ABSTRACT

AN INVESTIGATION OF TACTUAL APPARENT MOVEMENT

by Doris C. DeHardt

In previous studies concerned with apparent tactual movement, few
contributions were made toward an understanding of the phenomena in
question and the mechanisms responsible for their arousal; instead, the
results obtained by the early workers in the area were contradictory and
ambiguous. A multitude of methodological and theoretical shortcomings
were seen as the bases for this state of affairs. The purpose of the
present study was, by circumventing these shortcomings, to achieve such
an understanding. It was believed that an adequate test of each of the
following hypotheses was requisite to any complete understanding of appar-
ent tactual movement:

1) Stimulus conditions which satisfy the direct relation of TI and SS,
particularly at the extreme T13 and 853, are the conditions most
favorable for producing movement.

2) To secure maximum frequencies of apparent movement, it is not
necessary that conditions in which D is inversely related to TI
be used.

3) Frequency of on- skin movement is inversely related to TI and SS
jointly, suggesting that temporal and possibly Spatial summation
of neural activity from the two stimuli is necessary for the
eXperience of movement on the skin.

4) Frequency of off- skin movement is directly related to TI and SS
jointly, indicating that ”time and room" is needed to make it

feasible or logical to infer movement through the air.

Abstract Doris C. DeHardt

5) Cessation of 55 must occur (apparently before adaptation is
completed) so that both 8 onset and S Offset can be experienced
in order for apparent movement phenomena to occur.
6) An awareness of the departure of the stimulating objects from
the skin is necessary for the eXperience of off-skin movement.
Five (25, 3 males and 2 females (one of whom was not included in
the data analyses since she failed to report apparent tactual movement
experiences) were used in this study for one-hour periods on 14 separate
days. A Bartley kinohapt was used to present one- and two-point stimu-
lations to the volar surface of the forearm. A. drum, revolving at constant
speeds, upon which pawls were secured was used to achieve the desired
time intervals (T15) and durations (D5) of 55. The styli of the kinohapt
were released by activation of the solenoids, which in turn were activated
by microswitches that were tripped by the pawls. The spatial separations
between SS (855) were varied by moving the styli the apprOpriate distances
apart.
A total of 101 S conditions were presented to all 9s. TIs (from on-
set Sl to onset Sz) ranged from 0-600 msec. , Ds were 150, 300 and 5000
msec. , and 583 ranged from 1. 00-5. 00 in. Initially, 95 were instructed
to verbally describe their experiences; at a later stage of the experiment,
they indicated their experiences by selecting the appr0priate diagrammatic
representations from a key and/ or by drawing additional suitable repre-
sentations.
It was concluded that:
a) While the obtained relation of total amount of movement to T1 and
SS was only slightly in accord with the predicted relation, it was suggested
that it is more fruitful and enlightening to consider, separately, the re-

lations of on-skin and off- skin movement to TI and SS.

Abstract Doris C. DeHardt

U.‘

b) D need not be inversely related to TI in order to secure maxi-
mum frequencies of either on- skin or off-skin movement; D, in fact, is
not related to occurrence of on- skin movement and probably not to off-
skin movement either.

c) Frequency of on-skin movement is inversely related to TI, and
completeness of on- skin movement is inversely related to SS (and to T1
in minor degree). Both quantity and quality of on-skin movement are
heavily dependent on the degree of pliability of the skin tissue. A con-
ceptualization of the mechanisms involved in on- skin movement was given
which accounted for the on- skin movement results obtained, and which
greatly favored the notion that these mechanisms are peripheral in nature.

(1) Frequency of off-skin movement is directly related to T1 and SS
jointly for T1 sufficiently large. At small TIs, off- skin movement is in-
frequent, irrespective of the magnitude of SS. Thus, it was concluded
that "time a_nd_ room” is needed to make the inference of movement through
the air feasible and that neither "time" nor ”room" alone‘ is sufficient;
hence, it was concluded that off-skin movement experiences are the result
of the incitement of apprOpriate visual images.

e) The physical cessation of SS is not necessary for the occurrence
of apparent tactual movement phenomena.

f) Experiences of on- and off- skin movements are frequently accom-
panied by experiences of pick-up of the stimulating objects from the skin.
It is not entirely obvious why this association was true of on- skin move-
ment as well as of off-skin movement.

It was concluded that because on-skin and off-skin movements are
primarily aroused by different S conditions and were believed demonstrated
to depend on different mechanisms, a complete understanding of apparent
tactual movement cannot be achieved unless a distinction between the two

types of movement is maintained.

Abstract Doris C. DeHardt

A number of suggestions for future research in the area were made;
these indicate that additional studies in this area will prove to be extremely

interesting and enlightening.

Approved. «~- 3" Q/W “JR

Major Professor

Date MCX('75’

\J

 

AN INVESTIGATION OF TACTUAL APPARENT MOVEMENT

BY

Doris C. DeHardt

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

D OC T OR OF PHILOSOPHY

Department of Psychology

1961

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A C KNOWLEDGM ENTS

I am greatly indebted to Professor S. Howard Bartley for the
guidance and inspiration he has given me, not only during the course
of this investigation but throughout all of my advanced graduate train-
ing. I am grateful and proud of having been associated with him.

I also wish to thank Drs. Donald M. Johnson, Paul Bakan, and James
H. Stapleton for their assistance in this investigation.

To Mrs. Ardys Cox, Mr. Alfred Crowell, Dr. Thomas M.
Nelson, Miss Jane Ranney, and Mr. Thomas Trabasso, who con-

tributed many hours of their time as observers, I especially wish to
acknowledge my gratitude.

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ii

TABLE OF CONTENTS

CHAPTER

I. HISTORICAL REVIEW .................
II. STATEMENT OF THE PROBLEM. . . . . . .....
III. METHOD ........ . . . . . . ........

Observers .....................
Apparatus .....................
Procedure . ....................

IV. RESULTS ...... . . . . . .............

Relation of TI to SS . . .............
Relation of TI to D ...............
On- skin movement as a function of TI and SS .
Off- skin movement as a function of TI and SS .
Apparent movement in the absence of S offset:
d = 5000 msec. conditions ....... . . .
Experience of pickup of stimulating objects . .
One-point stimulations .............
Verbal reSponses ................
Results of conditions in which T1 = onset SI to
onset Sz interval. . . . . .........

V.‘ DISCUSSION ....................

UTHPUJNr—I

0‘

Hypothesis 1 ..... . . .............
Hypothesis 2 ....................
Hypothesis 3 ....................
Hypothesis 4 ....................
Hypothesis 5 .................. . .
Hypothesis 6 . ...................

v1. SUMMARY AND CONCLUSIONS . . ..........
REFERENCES ............. . ............
APPENDICES ..........................

iii

Page

1
16
20

20
20
25

33

34
36
36
39

45
47
48
48

49

55

55
56
57
60
61
62

70
74
77

LIST OF TA BLES

TABLE Page

1. Proportion of On-skin, Off—skin and Total Movement
ReSponseS at D : 150, 300,‘-and 5000 msec ....... 35

2. Relative Frequencies of the Three Types of On-skin
Movement at SS 2 1.00 to 4.00 in ............ 40

3. Relative Frequencies of the Three Types of On-skin
Movement at T1 (offset 5; to onset Sz) 2 -150 to 300
msec ......................... . . 4O

4. Perceived Nature of the Departure of the Stimulating

Object for One-point SS of D = 150, 300, and 5000
msec ................ . . ......... 48

iv

LIST OF FIGURES

FIGURE Page
1. A Bartley Kinohapt .................... 21
2. Theoretical PrOportion of Movement as a Function of TI

10.

11.

12.

for SS 2 1.00, 2.00, 3.00, and 4.00 in .......... 37

. Obtained PrOportion of Movement as a Function of T1

for SS 2 1.00, 2.00, 3.00, and 4.00 in. at D = 150 and
300 msec .......................... 37

Obtained PrOportion of Movement as a Function of T1
for all SSS Combined at D = 150 and 300 msec. Con-
ditions ........................... 37

. Theoretical Proportion of On-Skin Movement as a Func-

tion of TI for 882 1.00, 2.00, 3.00, and 4.00 in. . . . 38

. Obtained Proportion of On-skin Movement as a Function

of TI for SS = 1.00, 2.00, 3.00, and 4.00 in. at D = 150
and 300 msec. Conditions. . . . ............. 38

. Theoretical PrOportion of Off-skin Movement as a Func-

tion of TI for 552 1.00, 2.00, 3.00, and 4.00 in. . . . 41

. Obtained Proportion of Off- skin Movement as a Function

of T1 for SS = 1.00, 2.00, 3.00, and 4.00 in. at D = 150
and 300 msec. Conditions ........ . ........ 41

. PrOportion of Total, On- and Off-skin Movement for All

(_)S at D = 150 msec. as a Function of TI ......... 43

PrOportion of Total Movement for Each 9 at D = 150
msec. as a Function of TI ...... . .......... 43

PrOportion of On- skin Movement for Each (_)_ at D = 150

msec. as a Function of TI. . . . . . . . . . ....... 43
Proportion of Off- skin Movement for Each 9 at D = 150
msec. as a Function of TI ................. 43

LIST OF FIGURES - Continued

FIGURE Page

13. PrOportion of Total, On- and Off- skin Movement for

A11C_)_S at D = 300 msec. as a Function of TI ....... 44
14. Proportion of Total Movement for Each 9 at D = 300

msec. as a Function of TI ................ 44
15. Proportion of On- skin Movement for Each 9 at D = 300

msec. as a Function of TI . . . . . . .......... 44
16. Proportion of Off- skin Movement for Each 9 at D = 300

msec. as a Function of TI .............. 44
17. PrOportion of Movement that is On- skin Movement as a

Function of T1 for D = 150 and 300 msec. Conditions . . 46
18. PrOportion of On- and Off-skin Movement at D = 150

and 300 msec. as a Function of SS . . . . . . . . . 46
19. Proportion of On-skin Movement for Each 9 at D = 5000

msec. as a Function of TI ................ 46
20. PrOportion of Off— skin Movement for Each 9 at D =

5000 msec. as a Function of TI ............. 46
21. Proportion of On- Skin Movement as a Function of T1

for D = 150, 300, and 5000 msec. Conditions ...... 50
22. Proportion of Off-skin Movement as a Function of TI

for D = 150, 300, and 5000 msec. Conditions. . . . . . 50
23. Proportion of On-skin Movement as a Function of TI

for Individual 93 at D = 150 msec ........... 50
24. PrOportion of Off-skin Movement as a Function of T1

for Individual 95 at D = 150 msec. . . . ....... 50
25. Proportion of On- skin Movement as a Function of T1

for Individual 93 at D = 300 msec. . . . . . ..... 51
26. Proportion of Off-skin Movement as a Function of T1

for Individual 95 at D = 300 msec. ........ 51

LIST OF FIGURES - Continued

FIGURE

27.

28.

29.

30.

31.

32.

Proportion of On-Skin Movement as a Function of T1
for Individual 93 at D = 5000 msec ............

Proportion of Off-skin Movement as a Function of TI
for Individual Os at D = 5000 msec ............

Proportion of On- and Off-Skin Movement as a Function
of SS for All 95 at All Supplementary S Conditions. . . .

PrOportion of On-skin Movement and Bouncing for Each
9 at D = 150 msec. as a Function of TI. . . .

Proportion of On-Skin Movement and Bouncing for Each
9 at D = 300 msec. as a Function of TI ..... . . .

Proportion of On-Skin Movement and Bouncing for Each
9 at D = 5000 msec. as a Function of TI .......

Page

51

51

54

54

54

54

LIST OF A PPENDIC ES

APPENDIX
A. Response Key ......................

B. Data Sheet ........................

viii

Page
78

79

CHAPTER I
HISTORICAL REVIEW

Although apparent movement was of interest to researchers as early
as 1833 (Stampfer), it was Wertheimer, in his classic paper of 1912, who
gave impetus to the considerable concern for apparent movement which re-
sulted in the enormous number of investigations of the phenomenon in this
century, at first of visual apparent movement and then subsequently of
auditory and tactual apparent movement. In his paper, Wertheimer asserted
that the apparent movement in vision is a unique experience composed of .
unanalyzable “pure movement, " wherein no object is perceived and even
the attribute of quality is absent. The pure movement was called the "phi-
phenomenon, " and to account for it, Wertheimer suggested a physiological

explanation in terms of Kurzschluss, or ”short-circuits, " occurring within

 

the visual cortex. The school of Gestalt psychology credits its origin to
Wertheimer's experiment; its proponents accepted the phi-phenomenon as
an outstanding illustration of the non- additive configurations with which
they were concerned.

Korte (1915), in confirming Wertheimer's description and explanation,
presented laws or conditions (relating to the stimuli which arouse the phi)
necessary for the optimal occurrence of apparent movement. The primary
laws are: 1) Spatial separation and temporal interval are directly related;
2) Spatial separation varies directly with intensity; 3) intensity varies
inversely with temporal interval; 4) duration is inversely related to
temporal interval.

Many researchers attempted to verify Wertheimer's description and

explanation and Korte's laws for visual apparent movement. Among the

early workers were Benussi, 1917; Dimmick, 1920; Hillebrand, 1922;

and Higginson, 1926. Others (Burtt, 1917; Scholz, 1925; Mathieson, 1932)
attempted to determine whether the experience of phi could be produced
with the auditory modality, and if so, was auditory phi subject to Korte's
laws. Still other experimenters studied tactual apparent movement.

It is to those papers concerned with tactual apparent movement that detailed
consideration will now be given. As in the studies of visual and auditory
apparent movement, researchers in tactual apparent movement generally
attempted to determine: A) whether pure movement could be obtained,

B) whether there existed compulsory (mandatory) stimulus conditions for
the arousal of apparent movement, C) what the possible limiting range of
stimulus values capable of its arousal was, D) whether there existed
similarities of tactual apparent movement to visual and auditory, E) whether
Korte's laws were valid, and F) what the existential correlates of apparent
movement were.

Casual mention of the experience of tactual apparent movement was
made by Judd in 1896. Using successive two-point stimulations with
knitting needles, he found that when the second point was presented before
the cessation of the first "with the application of the second stimulus there
was sometimes simply an increase of pressure accompanied by a blunting
or diffusion of the sensation"(p. 428). VonvFrey and Metzer (1902), in
attempting to determine what time interval(s) minimize the difference
thresholds for two-point successive stimulations, obtained from their 9s,
descriptions of a "shifting" or ”stroking" of the stimulus along the skin.

Benussi (1913) made the first direct study of tactual apparent move—
ment, using a device which he built, called the Benussi kinohapt, for the
PuI‘pose of presenting successive two-point stimulations of varying
intensities (1), time intervals (TI), spatial separations (SS), and durations
(D) to the skin. The essential characteristics of the device were that tiny

rubber tips were mounted on stiff wires which were fitted to brass rods

and suspended vertically. The wires were activated by solenoids in such
. a way that when the circuit was completed through the coil of the solenoid,
the rod was expelled downward carrying with it the rubber-tipped wires
(the stimulating objects) which fell of their own weight upon the Skin.
When the circuit was re-made the rod, and with it the stimulus objects,

. retracted from the skin.

In his paper of 1913, Benussi reported obtaining tactual apparent
movement, and in his paper some of the descriptions of movement given
by his (_)_s are quoted. However, Benussi made little attempt to answer
the various questions posed regarding movement phenomena. Nevertheless,
in a study reported in 1917, he did so.

Using his kinohapt to present conditions with time intervals (from
onset S, to onset Sz) ranging from 0-2200 msec. , Spatial separations from
3-170 cm. , and durations of various fractional multiples of his TIs (which
he did not report) Benussi reported that with TI = 90-120 msec. and SS =
2-20 cm. fluttery "shiftings" within each of the successive areas were
aroused; with T1 = 240-260 msec. and SS = 3-12 cm. , "stroking" move-
ments were aroused between the first and second pressure spots; with
TI = 360-620 msec. and SS 2 3-20 cm.; "bow" movements, the experience
of something leaping through the air, were aroused. Benussi reported that
he suspected attitudinal factors were important in the perception of tactual
apparent movement because he found that immediately after movement had
been aroused at a given TI and SS, it could be aroused again with the same
T1 for different SSS. He also found an optimal constant ratio of 1:4 between
T1 and D. And although he stated that even the most definite movements
were of the most impalpable sort, he felt that pure movement was not
experienced. . Tactual apparent movement was, to Benussi, dependent upon
a temporal judgment of a supra-sensory order determined by processes of

memory.

Burtt (1917) investigated tactual illusions of movement with the
avowed purpose of verifying Korte's laws. In attempting to establish
whether duration is inversely related to time interval, conditions of D =
21, 42, 63, 84, 105 and 126 msec. and TI (from onset S, to onset 52) =
15, 21 and 40 msec.were presented to 4 (_)_s. (All possible combinations
of D with T1 were used in the experiment, but not all C_)s received all con-
ditions.) Spatial separation was held constant at 12 cm. Two 95 showed
a direct relation and two an inverse relation between D and TI', certainly
not evidence in support of Korte's law.

Burtt did claim evidence for a direct relation between SS and TI.
To put this law to test, he used time intervals (from onset to onset) of
15, 30, 45, 60, 75 and 105 msec. and spatial separations of 8, 12 and
16 cm. keeping D constant at 60 msec. Upon examination of the data
presented by Burtt in tabled form (p. 379), however, several deviations
from the purported relation can be noted, e. g. , movement occurred at
SS 2 16 cm. , TI - 60 msec. It appears that Burtt was a bit optimistic
about the conclusiveness of his results. There was a general increase
in movement as T1 increases up to 75 msec. , and a decrease thereafter,
1. e. at 105 msec.

The short-circuit theory was rejected by Burtt who suggested,
instead, that there may be a continuity of motor adjustment (e. g. with the
head and eyes) from S, to S; which gives the illusion of movement.

Whitchurch (1921) classified movement experiences into five types,
the first researcher in the area to attempt a classification. The five
types were: 1) full movement, in which the stimulus seemed to move from
the first to the second Spot stimulated; 2) bimembral movement, in which
the first and second stimuli each seemed to move; 3) unimembral move-
ment, in which either the first or second stimulus seemed to move;

4) intramembral movement, in which the stimulus at one or both Spots

seemed to move within the area of stimulation; and 5) pure phi, in which

the apparent movement had no qualitative, intensive or extensive beginning
and ending, but was a uniform "brushing" over the cutaneous surface.

In her principal experiment, using 4 Os, Whitchurch used D = 150
msec., TI (from onset SI to onset 52) = 25, 50, 75, 100, 250, 500, 750
and 1000 msec. and SS = 2.1-5. 5 mm. conditions. Not all 93 received all
S combinations. The maximal amount of full movement was reported at
TI 2 150 msec. The frequency of all types of movement increased up to
50 msec. , remained nearly constant until TI = 250 msec. , and decreased
continually after 100 msec. It is well to note here that Whitchurch was
concerned only with cutaneous or ”on-skin” movement and not "off- skin"
or bow movement. She restricted herself to tiny Spatial separations so as
to avoid visual association, which is necessary for the experience of bow
movement.

To two of her 4 OS, Whitchurch presented a few conditions of
D = 75 and 200 msec. Incidence of full movement was less for these dura-
tions than for 150 msec. duration conditions. She did not report amount
of other types of movement at these durations.

Whitchurch theorized very little in her paper, but she stated that a
higher perceptual order is involved in tactual apparent movement than in
visual apparent movement, so that there is less probability of determining
compulsory conditions for the tactual. Some of her 98 reported that they
experienced pure phi.

‘ Andrews (1922) attempted to obtain Optimal conditions for bow move-
ment. He presented conditions of D = 150 msec. , TI (from onset S, to
onset 82) = 100-1600 msec. and SS = 2, 6, and 10 cm. He presented no data
in quantified form (only some typical introspective reports were given), but
Andrews stated that no quantitative relations could be established. He, like
Benussi, suggested the importance of the prOper subjective attitude. One
trained _O_ reported apparent movement on 45% of the presentations. Two

untrained 9s reported none until the phenomena were indirectly suggested

by rapidly repeating the conditions in close succession. Andrews con-
cluded that the perception of movement in or on the skin is inferred from
a Spatial and temporal integration of pressure, and that this perception is
of a type different from the subjective processes which carry the meaning
of bow movement through the medium of associated visual and kinesthetic
images.

In a study primarily concerned with comparing the phenomenal
extent, i. e. , the perceived length, of apparent movement in vision, audition
and touch, Scholz (1925) reported no strict regularity in the relations
governing optimal movement, and his results contradicted Korte's space-
time law (in contrast to Burtt's purported verification of it). He presented
conditions with TI (from offset 81 to onset 82) = -150 to 900 msec. , SS = 2 to
16 cm. , and D = 150 msec. Scholz explained apparent movement by the
Hartmann-KOhler modification of Wertheimer's theory.

The purpose of a major investigation by Hulin (1927) was ". . . to
determine the possibility of compulsory conditions for the arousal of
tactual apparent movement by a succession of temporally and spatially
discrete stimuli. The limiting range of values was sought which would
arouse tactual movement” (p. 293). He used a modified form of Benussi's
kinohapt to present stimuli which were always of duration 150 msec. ,
were Spaced temporally (from offset 8, to onset 52) from -150 to 300 msec.
and spatially from 5 to 150 mm. Not all (_)s received all stimulus combi-
nations. The 93 were asked to draw a graphic representation of each
cutaneous perception aroused. The possible impressions were character—
ized by Hulin as being of three classes, simultaneous, successive, and
movement. Diagrams of various types of experiences within each of these
three classes were given to 93, and were to be used by them as a key or
guide for their graphical reporting. That is, 93 were told to draw their
characterizations as nearly as possible according to the symbols shown

in the key; however, if they found the key inadequate, they were to draw

any additional suitable diagrams. A few of the diagrams used in the
present study were those used by Hulin (see Appendix A, diagrams A1,
A2, A5, B1, B5, C1, C2, C3, C8, C12).

Hulin sub-divided movement into three different types in his dia-
grams. These were a) full, identical with Whitchurch's full movement,
b) end, combined Whitchurch's bimembral and unimembral movement,
and c) bow, defined as Benus Si defined it, i. e. a sort of leaping through
the air. An additional type of movement was added by some of Hulin's
OS and was the type that Whitchurch called intramembral movement.
Hulin called it inner movement.

Like Whitchurch, Hulin was interested primarily in the conditions
producing full movement. He found the maximum amount of it at T1 =
-75. For D = 150 msec. which Hulin always used, this is, then,
equivalent to a 50% temporal overlap for the two 83 which correSponds
to an internal of +75 msec when TI is measured from onset to onset.
Further, he reported a steadily decreasing frequency of full movement at
successively longer TIs. Precisely the same results were obtained for
all types of movement combined. There was little difference in fre-
quency of movement as a function of Spatial separation except for that of
150 mm. , where little movement occurred. The highest frequency of
movement was obtained for conditions of SS = 70 mm. Therefore, Korte's
suggested direct variation of time and Space was not verified. In fact,
Hulin felt that the only quantitative relation shown by his data was that
the time interval of -75 msec. ". . . is exceptionally favorable for the
arousal of apparent tactual movement" (p. 320).

By way‘of theorizing, Hulin stated that ”. . . the apparent tactual
movement consists of a perceptual complex which involves at least four
persistent though variable factors; the peripheral factors of (i) pressure
irradiation and (ii) perseveration, and the subjective (associative) factors

of (iii) visual imagery and (iv) kinaesthesis" (p. 320).

Neuhaus (1932) used a modified Benussi kinohapt to present two-
point stimulations of various time intervals, spatial separations, and
durations. He obtained illusory movement for time intervals ranging
from 0 to 500 msec. His results suggested verification of Korte's Space-
time relation. And he found that when distance and time were held constant,
movement was most likely to occur at either long or short stimulus dura-
tions. Some 95 failed at all times to report apparent movement. Neuhaus
was also concerned with the Speed and direction of apparent movement,
but since the present paper is not directly concerned with these matters,
discussion of them will be foregone.

Neuhaus rejected physiological theories of apparent movement
phenomena and said instead that, "Apparent movements are of a psycho-
logical nature" (p. 551). Two of the several arguments he gave for this
view were: 1) the occurrence of apparent movement is dependent upon
will, set and attention, so it cannot be physiologically determined, and
2) stimulus conditions are, in themselves, inadequate to explain the
phenomena. Kelly (1935) subsequently, and Benussi (1917), and Andrews
(1922) previously reported evidence to support the first argument.
However, because the statement in 2) is true of the present state of affairs,
it does not necessarily follow that physiological mechanisms cannot account
for apparent movement. Perhaps, by a new experiment, the state of
affairs will be reversed.

Neuhaus' was the last serious attempt to answer the questions posed
by the early workers in apparent tactual movement. Since his report ap—
peared, a few studies bearing only slightly on these questions have been
repOrted. Schaeffer (1939) presented diffuse stimulations to various areas
of his 95 Skin by means of a shower bath of moderate pressure, using a
shower head with varying numbers of holes. Apparent movements were
reported and were described as Spirals and linear to-and-fro surges.

Individual differences were marked. In most cases, movement of the body

changed the direction of the apparent movement, and voluntary acts, loss
of sleep, and treatment of the skin with ultra-violet light modified. the
spirals and surges. Schnehage (1939) used nearly Simultaneous,
rhythmical, alternating SS to ascertain whether blind 95 experience tactual
apparent movement on various parts of the body as do normally- sighted
95. He reported that they did.

Several studies and theoretical papers, in addition to those already
mentioned, dealt with and discussed the importance of attitude, set,
learning, and motivation in the determination of apparent movement
(Pieron, 1934; Ryans, 1937; Lehrnann, 1939; Jones and Bruner, 1954;
Toch and Ittelson, 1957). All of these authors believed that, because of
the influence on movement phenomena which these subjective factors were
shown to have, Gestalt theory attempting to account for movement was
heavily discredited.

In all of the studies of apparent tactual movement heretofore, it
has been assumed that the effective stimulus for pressure sensations is
Simply contact upon the skin by an object with supra-threshold force.

If one held the skin depressed at a constant level for a period of time, it
was usual to assume that such constituted a continuance of stimulation or
a constant stimulus, and it was assumed that the release or removal of
that object making the depression was cessation of stimulation. Nafe and
Wagoner (1941a, 1941b) (and others less significantly) have since Shown
that such a conceptualization of the adequate stimulus for the tactual
modality is not entirely accurate. Nafe and Wagoner found that it was not
the deformation of the skin, .31 s_e_, but rather the process of deformation
which is necessary for stimulation. More specifically, it is the process
of deformation occurring at or above a critical rate which constitutes
stimulation. They concluded thusly:

The present experiment indicates that any force exerted against
the pliable tissues sensitive to pressure will be effective as a
stimulus as long as it sets up movement of the innervated tissue

10

above a minimum in amount and rate. . . . If stimulation is pro-
duced by releasing a pressure from the tissues instead of by
applying it, the same result, i. e. a movement of the tissue, is
obtained due to the elasticity of the tissues and the effect for
sensation is the same. (1941b, p. 349)

(They found that a sensation was usually reported upon the release of the
pressure, but not always. The fact that some of their kymographic
records of the rate and amount of deformation and re-formation showed
that recovery (re-formation) was not immediately completed, i. e. the
amount of movement in re-formation was less than in deformation, would
account for this. It was reported that amount of recovery depended on
magnitude and duration of pressure.)

This new conceptualization of what constitutes an adequate tactual
stimulus has great significance for studies of apparent tactual movement,
or any tactual study for that matter. In all of the previous studies (except
Schaeffer's), two-point stimulations were used. But since an object can

stimulate when it deforms and when it reforms, it is possible that, in

 

actuality, four stimuli were unwittingly being presented. And if the stimu-
lating objects failed to move the Skin at or above the critical for any length
of time while they made contact with the skin, then the actual durations

of the stimuli were not what they were purported to have been. The nature
of the stimulus for touch as we now know it,. must surely be taken into
account, then, if any real understanding of apparent tactual movement is
to be realized.

From the historical review, it is clear that the questions set forth
for examination in the several studies were by no means unequivocally
answered. Indeed, it is difficult to make any statement regarding the
status of tactual apparent movement other- than that it is highly ambiguous.
The fact that so little can be made of the results of the previous studies
is undoubtedly due, in part, to the procedural dissimilarities, i. e. dis-

. 0 a o . o O O
Similarities of apparatus, observers or Os, stimulus conditions, and

11

treatment of results, in part to the inadequacies of same, and in part to
the fact that the questions were generally misstated, i. e. stated in such
a way that they were unanswerable.

It is probably always the case that procedural dissimilarities among
studies contribute to dissimilar results. It seems certain that this was
true of the apparent tactual movement studies, in which dissimilarities
were the rule rather than the exception. Some of the relevant differences
were:

a) hairs, blunt rubber-tipped rods, and pointed rods or needles

were used as stimulus objects,

b) 93 were sometimes naive, sometimes highly SOphisticated,
particularly in those studies in which E also served as an 9,

c) some researchers marked the Skin (the forearm was always used,
if not other areas in addition), and stimulated only the marked
areas, but most did not,

d) Burtt removed hair from (_)_s' arms, but no others reported
having done this,

e) random orders were used wholly or partially by some workers,
and not at all by others,

f) several different types of movement were defined and occasionally
at least a few of these were treated separately by some investi-
gators, while others were concerned only with incidence of move-
ment in general.

g) only in the study by Burtt (1917) was mention made of dampening
(or attempting to dampen) auditory stimuli from the timing devices,
and only Burtt and Hulin shielded the apparatus from 93 View, or
at least only they mentioned having done so,

h) the 93 in some studies served several hours a day, in others
only one hour per day (Whitchurch did not even mention the length
of her experimental sessions or how many there may have been

in a single day),

12

i) in some studies (23 received all possible S combinations and in
others they did not,

j) treatment of results varied widely from paper to paper,

k) the conditions themselves varied considerably as to time interval,
duration, Spatial separation, and undoubtedly intensity, also,
although rarely was the intensity of S mentioned.

Methodological differences thus were legion; it is not surprising
that some procedures were less adequate than others. The inadequacies
of certain of the procedures and some shortcomings common to all the
studies will now be indicated.

In the studies which made use of Os who knew the purpose of the
experiment in which he participated, and this was true of most studies
using SOphisticated 98, results could have been biased owing to the highly
suggestible nature of apparent tactual movement phenomena. It was found
by this writer (in preliminary experimentation), and in all likelihood by
others also, that a practiced 9 is required in an experiment involving
tactual apparent movement in order to obtain reliable reports (probably
because movement experiences are often hazy, transitory and strangly
unreal). However, the practiced 9 does not imply the knowledgeable 9.

It seems to me that 93 would best be treated by telling none of them the
purpose of the experiment, giving them all the same amount of practice
on the same conditions prior to the experimental conditions, and by estabu
liShing and defining certain reSponse categories (Similar to Hulin's
technique, for example) for them so that all 98 will use identical criteria
for the classification of their reSponseS, thus making it possible to

justifiably compare and combine 93' reports. This was rarely possible

 

in previous studies. And while it is true that the nature of the experiment
is suggested to 9 by giving him a number of diagrams by which he is to

categorize his responses, the purpose, nevertheless, remains obscured.

13

Since Benussi (1917) suggested that having gotten movement on a
preceding condition can alter the probability of obtaining movement on a
succeeding condition, it goes without saying that randomization of con-
ditions is essential.

Failing to stipulate criteria which differentiate the several types
of apparent movement as did some of the early workers, in addition to the
aforementioned shortcoming, also had the disadvantage that it served to
lessen the likelihood of achieving an understanding of movement phenomena.
All types of movement were combined into single frequency distributions,
obviating the possibility of establishing that different stimulus conditions
account for different types of movements. This seems particularly true
of on-skin versus off- skin movement. These are very different experi-
ences. Could not different conditions have given rise to them? Recall
that Benussi (1917) found on- skin movement at relatively short time inter-
vals, off-skin movement at relatively long time intervals. And Andrews
(1922) suggested that these two major types of movement were the result
of different processes. Do not the S conditions presented at a particular
time determine which processes are involved at that given time?

In experimentation preliminary to the present study, I found that
being able to hear the timing devices which determine the release of the
stimulating objects to the skin (in this case miCroswitches), altered the
amount of movement experienced. For conditions of relatively short time
intervals, the probability of movement was increased, apparently because
the "clicks" from the two microswitches had a rhythmical quality which
was interpreted tactually as a smooth, rolling motion. For relatively longer
time intervals, the clicks seemed to enhance the discreteness of the two
tactual stimulations, because the amount of movement was lessened.

It was also found that being able to see the needles drop onto the arm de-
creased the likelihood of experiencing movement. In other words, when

relevant auditory and visual stimuli accompany the tactual stimuli,

14

curiously biased reports of apparent movement can result, so it is essential
to eliminate such auditory and visual stimuli.

Presenting up to 500 trials per day as did Burtt, leads one to wonder
whether fatigue and boredom might not have influenced the results obtained.
It seems ill-advised to have more than one or two hours a day of experi-
mental participation so as to avoid such complications. And intertrial
intervals were uniformly not reported. If they were very Short, fatigue
again might have been a complicating factor.

Part of the failure to answer the questions posed in these studies was
due to the generally inadequate treatment of results. In the papers in
which only sample introspections were reported, it is not possible to express
quantitative relations between and among stimulus conditions. Most often,
the raw data in the form of key words describing the experiences, e. g.
series, flow, snake effect, were presented. But even in these cases it is
difficult to determine just exactly what types of movement were experienced,
because what connotations the key words had to the user(s) is not always
obvious. Hulin presented his results in graphical form, but Since not all
9s got all conditions, the value of such a treatment for inferential purposes
is questionable. Because the results from every previous study indicate
that the absolute amount of movement varies considerably between 93,
failing to give all 98 all conditions in an eXperiment renders it impossible
to make meaningful frequency distributions of movement (as a function of
time interval, for example), either for individuals or for the group.

None of the previous researchers reported the degree to which their
timing devices were accurate. Although there is no particular reason to
be suspicious, it Should be pointed out that unless extreme care were
taken to achieve and maintain accurate timing, the time intervals and
durations may have been in error (i. e. , not what they were purported to
have been). It is impossible to tell whether such care was taken and

simply not reported, or whether it was absent altogether in these studies.

15

At any rate, conditions whose temporal characteristics are of the order
of milliseconds are very precisely timed conditions, indeed.

The early workers surely would have obtained more fruitful and
conclusive evidence in support of their views if they had asked questions
which were more amenable to experimental examination. The question,
what are the existential correlates of apparent movement, while of a sort
common to the introspectionist of the early 20th century, seems meaning-
less to uS now. And how can one be sure he has or has not experienced
pure phi? There seems to have been some doubt about just how unreal it
is; conclusions as to whether phi occurred or not seem to have depended
on the judgments of the experimenters.

It was particularly unfortunate that the early researchers sought
compulsory conditions for the arousal of apparent movement. Very few
psychological antecedent events result in totally certain‘outcomes, in fact,
not a single example of such comes to mind. One must be content in
psychological research to seek out conditions which have higher or lower

response probabilities than other conditions.

CHAPTER II

STATEMENT OF THE PROBLEM

Inasmuch as the previous studies were frought with these
several methodological and theoretical difficulties, it is not surprising
that few positive contributions regarding apparent tactual movement were
made. If one were to execute a methodologically sound experiment,
however, a number of questions, meaningfully stated and worthy of being
entertained, could be put to test. Such is the purpose of the present
investigation. It is hOped that as a result, our knowledge and understand-
ing of apparent tactual movement specifically, and the tactual modality in
general, will consequently be enhanced. The questions are the following:

1) Can stimulus conditions be identified which have high probabilities
of producing apparent tactual movement? Are stimulus conditions which
satisfy Korte's Specifications those which have high movement reSponse
probabilities? And what conditions, if any, are not likely to be associated
with reports of movement?

2) Do movements on- skin and movements off-skin tend to occur under
different types of stimulation? What are the stimulus conditions associated
with the two classifications of movement?

3) Assuming l), is it possible to infer what are the physiological
and psychological mechanisms of apparent tactual movement? And as sum—
ing 2), can one infer that different mechanisms are Operating for on- and
off- skin movement? In other words, are there characteristics of the high
reSponse- probability stimulus conditions which suggest the Operation of

certain mechanisms as Opposed to others?

16

17

4) Is the offset of S, which we now know is not cessation but continu-
ation of S or restimulation, necessary for apparent movement? Is it
necessary for on- and off-skin movement, or just for one and not the other?

5) Is the experience of pickup, i. e. the awareness of the withdrawal
of the stimulating objects, necessary for apparent tactual movement, both
of the on- and off-skin variety, or is it necessary only for off-Skin (or on-
skin) movement?

To ascertain more definitely the ranges the several S variables
require, a pilot study was conducted prior to the present investigation.

All possible combinations of TI (from offset S, to onset 52) = -150, -75, 0,
75, 150, and 300 msec.; D1: 75, 150, 300 and 5000 msec. (the latter mean—
ing no offset prior to adaptation); and SS = 1. 25, 2. 50, 3. 75, and 4. 50 in.
were presented to one 9 in semi-randomized order in one-hour sessions.
An average of 10 conditions were presented per session, with one session
per day. 9 was asked to describe or relate everything he experienced.

(See p. 25 of the Procedure for details; the procedure in the pilot study

was similar to that of the present study.) C_)s reports suggested the following:

a) There are conditions which have much higher response probabilities
than others. Specifically, A) the shorter the time interval, particularly
for short Spatial separations, the greater the frequency of movement, and
B) the longer the temporal and spatial intervals, the greater the frequency
of movement. Thus, Korte's space-time relation seemed valid.

b) The movement which was reported with type A conditions was
almost entirely on- skin movement, and many of the movement responses
to type B conditions were of the off- skin variety.

c) Movement occurred with approximately 50% of the conditions of
D = 75, 150 and 300 msec. The maximal amount of movement for D = 75
occurred at TI = 0 and 75, for D = 150 at T1 = 150 and for D = 300 at T1 =
-150, suggesting that optimal movement is not necessarily obtained for

conditions where D is inversely related to TI.

18

d) The results in b) seem to suggest that on- skin movement may
depend for its existence on neural temporal and, possibly, Spatial summa-
tion, and that the visual imagery associated with off-Skin movement is
enhanced by ”Spreading out" the two stimuli in Space and time. It would
seem likely, though, that if the temporal and/or spatial intervals were
increased to a sufficient extreme, reports of movement would cease.

e) No movement was reported for conditions of D = 5000 msec.

9 reported very infrequently that he experienced pickup; however, in these

 

cases he stated that since pickup occurred after he no longer felt the
objects on his skin (i. e. adaptation had taken place), it seemed to him as
though pickup were just another 8 presentation.

f3) 9 was not asked to report whether he was aware of pickup on any
conditions except those of D = 5000 msec. However, it is believed that
an awareness or experience of pickup is necessary for off- skin movement.
That is, perhaps movement through the air is experienced because the
pickup is experienced (particularly of SI) and one simply infers that the
first S continues through the air and strikes again. (This supposition was
borne out by some of 9's verbal descriptions. For example, he reported
an experience which was like "a bird sailing through the air which touched
down with its feet in two places. ”

From the results of the pilot study and to a lesser extent from the
previously reported studies, the following hypotheses, which are the
experimental hypotheses of this study, are suggested:

1) Stimulus conditions which satisfy the direct relation of TI and SS,

particularly at the extreme TIS and SSS, are the conditions most favorable

 

for producing movement.
2) To secure maximum frequencies of apparent movement, it is
not necessary that conditions in which D is inversely related to TI be

used.

l9

3) Frequency of on- Skin movement is inversely related to T1 and
SS jointly, suggesting that temporal and possibly Spatial summation of
neural activity from the two stimuli is necessary for the experience of
movement on the skin.

4) Frequency of off- skin movement is directly related to TI and
SS jointly, indicating that "time and room" is needed to make it feasible
or logical to obtain movement through the air.

q 5) Cessation of 58 must occur (apparently before adaptation is com-
pleted) so that both S onset and S offset can be experienced in order for
apparent movement phenomena to occur.

6) An awareness of the departure of the stimulating objects from

the skin is necessary for the experience of off- skin movement.

CHAPTER III

METHOD

Observers. --Five 95, 3 males and 2 females, ranging in age

 

from 22-37 years were used. Three were psychology graduate students,
one a research associate in psychology and one an undergraduate senior
psychology major. Since all 93 were psychologists or aspiring psy-
chologists, they were sufficiently SOphisticated psychologically to be able
to ascertain the nature of the experiment. All of them knew that the
experiment in some way dealt with tactual experiences and that primary
among those of interest were movement experiences. However, none of
them was aware of the specific questions with which the study was concerned.
Each 9 was asked at the end of his final participation period to state what
he thought the experimental hypotheses of the study were. None gave

even a fair approximation of any of the hypotheses.

 

Apparatus. --A Bartley kinohapt (see Fig. 1) was used to present
the stimuli to the volar surface of the forearm. Although, as can be seen
in Fig. 1, the kinohapt can be used to present three stimuli, in this
experiment either one or two only were presented on any given trial.

The styli in this experiment were size 14 Singer sewing machine needles.
Horizontal and vertical adjustments of the solenoids were made with knobs
3 and 4 as shown in Fig. l. The left- and middle-positioned styli were
always used in this experiment. It was possible to separate these styli
vertically by distances ranging from 3/4 to 5 1/4 in. The solenoids were

activated by microswitches and were wired in parallel. The microswitches

20

Fig. 1.

 

 

A Bartley Kinohapt. Item 1 is the knob for adjusting the
whole carriage vertically; 2 is one of the solenoids activating
a stylus; 3 is a solenoid carriage adjustable horizontally;

4 is a knob adjusting a single solenoidyertically; 5, the arm
rest, adjustable in all directions; 6, the arm-rest lock.
(From Principles of Perception, Fig. 17.4, by permission
of S. Howard Bartley.)

 

22

were tripped by pawls on a revolving metal drum. Tripping the switches
opened the circuit, releasing the styli to fall of their own weight (S, =

. 365 gr. , S; = . 340 gr.) to the skin. (The time lag from circuit opened

to the complete fall of a stylus was no more than 13. 5 msec. , and like-
wise, for the lag from circuit closed to complete retraction. This was
established by determining the maximal number of full falls and retractions
which could occur in a given length of time. It was found that a single
release and retraction, for each stylus, required approximately 27 msec.
Assuming that the time of release and of retraction are identical, which
seems plausible, but was not definitely established [It looked as though the
two processes took place with similar speeds, but at these speeds, the
visual system is not sufficiently acute.], then each process required about
13. 5 msec. If the processes were completed in identical times, then the
lags were of no significance; the stimuli simply occurred the length of

the lag later in time than supposed. The actual lag from circuit opened

to contact of stylus upon the skin, and from circuit closed to withdrawal
from the Skin, was somewhat less than 13. 5 msec. , because both styli
were adjusted on every trial so as to be only 1/4 in. from the skin [in the
retracted position, of course]. The distance of the full fall of the styli,
however, was 3/4 in.).

The microswitches were mounted on posts carried by a ring con-
centric with the bottom edge of the drum. Their heights could be adjusted
so as to have the microswitches activated by the necessary pawls required
for duration variations. The posts, and consequently the microswitches,
could be moved horizontally around the ring by loosening the clamps which
secured them. The positions of the two microswitches could thus be
varied so as to provide a wide range of time intervals between SS.

Stimulus durations of 150, 300 and 5000 msec. were chosen for use
in this study. For conditions consisting of two stimuli, S, and 52, the

duration of S, always equalled almost that of 52, since the weights of the

23

styli were almost equal and were never varied in this experiment. To
present stimuli which would make contact with the arm for these lengths
of time, the following scheme was used: the aforementioned drum, which
had a circumference of 18.06 in. , was driven by a Cenco Stirrer (variable
Speed, 115 V) at constant Speeds. That is to say, the speed of revolution
could be varied by changes in pulley size, but once a size was chosen,

the Speed remained constant. Knowing the circumference of the drum and
the speed at which it traveled, then, it was possible to compute the length
of pawl necessary to provide a duration of any magnitude. By taking into
account the possible error in measurement of the pawls for D = 300 msec.

conditions, the possible error due to the difference between "time on" and

 

"time off" lags, errors made in measuring the drum circumference and the
slant of the pawls, and the error made in timing the drum Speed (3:. 5 msec. ),
it was ascertained that a duration of 300 i 20 msec. was maintained,
for D = 300-msec. conditions, throughout the experiment. To present
D = 150 msec. conditions, the D = 300 msec. pawls were also used and
the Speed of revolution was doubled. Conditions of D = 150 msec. were
accurate, then, to 150 i. 12. 5 msec. Another pair of pawls was used for
D = 5000 msec. conditions. These durations were accurate to 5000 + 500
msec. It would be well to point out here that accuracy was not quite as
important at D = 5000 as at D = 150 and 300 msec. , because adaptation
takes place before cessation of SS. (This is suggested by Nafe and
Wagoner's data (1941b), and it was also borne out by a great deal of pre-
liminary investigation into the matter, and subsequently, by the intro-
spective reports of the 98 used in the present study. The same sources
of evidence, with particular emphasis on the former, were used to
ascertain that complete adaptation does not take place before cessation
of stimuli whose durations are only 150 and 300 msec.)

The various time intervals between SS were achieved by rotating

one of the microswitches around the frame on which it was secured until

24

the appropriate distances between microswitches, and consequently the
onsets of the two 85, were reached. Only one microswitch was moved to
achieve any given T1, the other remained in constant position. The
appropriate distances between the rollers for each T1 were determined;
then these distances were marked on the drum so that possible time
interval errors would be constant or nearly so. The TIS for D = 300 and
5000 msec. conditions were accurate to i 13 msec. and for D = 150 msec.
to i 9 msec.

The metal drum and its associated paraphenalia were completely
housed in a fibre board box lined with cotton batting, in order that the
”clicks" produced by activation of the microswitches be greatly reduced in
intensity. About two-thirds of the front panel was hinged so that access
could be made to the interior for the purpose of making the necessary
manipulations to the microswitches. A 7. 5 W. lamp was suspended
from the roof of the box.

Other materials used in this experiment were the following: A 2'x3'
screen of black cloth tacked to a wooden frame was used to shield the
kinohapt from 9's view when he was in testing position. A black box
covered the kinohapt until C_) took this position; after he did so, the box
was removed by _E_.

95 were tested in supine position on a 2 l/2'x5' table which was
placed parallel to the one on which the kinohapt was located. To insure
_OS' comfort, an air mattress and several pillows were used. To make
the arm rest more comfortable a strip of foam rubber the length of the
arm rest was inserted in it. _ An Ace elastic bandage was used to secure
C_)'s arm in position. 7 The kinohapt rested on a sheet of foam rubber so
that the table would not serve as a resonator for the sound waves gener-
ated by the action of the solenoids (which otherwise were inaudible to 9).

The distance between the two needles was measured by a ruler with

1/50 in. separations. Vernier calipers were used to measure the distance

25

of the needles from (2's arm. A device similar to a bed serving tray,
except that the top slanted down toward 9 at a 600 angle, was used in

the portions of the experiment which necessitated 9's writing. 93' stimu-
lated arms were swabbed with alcohol at the outset of each session (though
this proved to be unnecessary). . Cotton and ear muffs were used so that

9 perceived absolutely no auditory SS associated with the apparatus.

Procedure. --Stimuli of D = 150, 300 and 500 msec. , SS = 1.00, 2. 00,

 

3.00, 4. 00 and 5. 00 in., and TI from offset S, to onset 82 (for D = 150 and
300 conditions) = -150, -75, 0, 75, 150, and 300 msec. , and TI from onset
to S, to onset S; (for D = 5000 msec.) = 0, 75, 150, and 300 msec. were
used. The following are the two—point stimulations which were used: All
possible combinations of D : 150 and 300 msec. , SS 2 1.00, 2.00, 3. 00,
and 4.00 in. , and T1 = -150, -75, 0, 75, 150, and 300 msec. were pre-
sented, a total of 48 different conditions. Conditions of D = 5000 msec.
were combined with SS = l. 00, 2. 00, 3. 00, and 4. 00 in. and TI (fron onset
to onset) = 0, 75, 150, and 300 msec. for a total of 16 unique conditions.
In addition, all three durations were used with T1 = 300 msec. and SS = 5. 00
in. , so there were three conditions of SS = 5. 00 in. And finally, one-point
stimulations were presented, two for each duration or Six in all. There
was a total, then, of 73 conditions.

98 were run on 14 separate sessions; all except the first two
sessions were approximately one hour in length (the first two were shorter).
All 93 except AC had one session per day, Six sessions per week.
Observer AC had two sessions per day, twelve per week. Her same-day
sessions were one hour apart. (This treatment of AC was, unfortunately,
a necessary concession to her participation in the experiment.)

Each 9' s 14 sessions were held at approximately the same hour
each day. Two Os were run at the early to mid-morning hours, two were

run in mid-afternoon, and the other was run at the late afternoon to early

 

26

evening hours. The first two sessions were orientation sessions, the next
six were practice sessions, and the final six were experimental sessions.

Fourteen conditions were selected randomly from the total of which
six were presented to 93 on the first session and eight on the second
session. These 14 conditions were used to orient Os to the experiment
and the experimental conditions. After the orientation sessions, two
complete sets of the 73 conditions were presented, the first set as practice
conditions, the second set as experimental conditions.

Two sets of semi—random orders of the 73 conditions were made up
for each 9. The orders were determined thusly: Twelve conditions were
presented on five of the practice and experimental days and thirteen on
the remaining day. Seventy-three slips of paper of equal Sizes, each
Specifying a stimulus condition, were made up. All conditions of D = 150
msec. were clipped together as were those of D = 300 and 5000 msec.
These three bundles were placed in a Shoe box and shaken. Two of the
three were selected for use on a single session. Each one selected was
separately unclipped, placed back in the box and shaken, and then 6 con-
ditions were drawn from the box; consequently, 6 conditions each of two
durations were chosen for a single session. (The split was not exactly
6—6 on one or two of the sessions since there were fewer D = 5000 than
D = 150 and 300 msec. conditions.)

The conditions were not completely randomized Since a great deal
of time was required to manipulate the apparatus from condition to con-
dition for all three stimulus variables. It was decided to only partially
randomize duration for two reasons. . First, because the variable of
duration was not believed to be as crucial or significant in the determin-
ation of apparent movement as were the other S variables, as indicated
by the results of previous studies and those of the present author's pilot
study, and second, it took longer to manipulate the apparatus for changes
in D than for the other variables, since to change from D = 150 to D = 300

and vice versa, it was necessary to change gear size and this change

 

 

27

necessitated a check on the drum speed. (Before each session and in
mid-session when D was changed, the drum speed was carefully checked
so that the Speed of the drum was always 2450 i 5 and 1225 i 5 msec.

Each condition, when it was presented, was presented 3 times in
succession. For the D = 150 and 300 msec. conditions, each of the three
trials constituted two identical successive stimulus presentations, that is
the drum revolved twice when conditions of these durations were being
presented. Two presentations were given because in preliminary investi-
gation, it was found that with conditions this short in time, C_)_s had dif-
ficulty making reliable reSponses, since, as the pilot study 9 reported,
"The stimuli had come and gone almost before I realized I was stimulated. "
98 were told to respond only to the second presentation, if possible, and
that the first one was simply to alert them to the impending arrival of
the second. Only one presentation per trial was given for D = 5000 msec.
conditions, since it was expected that if two presentations were given,
the Skin would not recover sufficiently after the first for the second to be
perceived as clearly and vividly as the first.

As already stated, the same conditions were given in practice
sessions as were given in the experimental sessions (although the orders
were different). The responses made during the practice sessions were
verbal responses; 93 were told to describe or relate their tactual im-
pressions in their own words. During the experimental sessions, 95
reported their impressions by selecting the appropriate characterizations
from a key (Appendix A). Further elaboration of the different procedures
used in the practice andexpe’r-imental sessions is forthcoming; the dif-
ference is suggested here so that the purpose of the two types of sessions
can be explicated. The principal purpose of the practice sessions was,
of course, to develop previously inexperienced 98 (with respect to
participation in a tactual study) into practiced 95. The reports from

these sessions also were used to aid in the determination of which diagrams

28

would be most suitably included in the key to be used in the succeeding
portion of the experiment. All of OS' verbal reports were recorded by
E with paper and pen. So although a complete set of verbal reports for
each _O_ was thus obtained, it was believed that these reports would not
suitably be considered as constituting primary data, subject to analytical
operations performed for inferential purposes. The results from the

experimental sessions were so considered. The bases for these desig-

 

nations were that in the practice sessions, a) the degree of Skill in report-
ing changed, probably exponentially, b) 95 did not have a common set

of criteria for responding, and c) the classification of the verbal responses
depended, too often, on E's interpretation of them, while in the experi-
mental sessions, the procedure used was assumed to have obviated these
difficulties. However, the intention was to use the verbal reports to
establish, though only roughly perhaps, the degree of consistency of 93'
responses.

The first 8 days of experimentation, consisting of the orientation
and practice sessions were called Part I of the experiment. At the outset
of the first session of Part I, 98 were given the following instructions to
read:

This study is concerned with the tactile or touch modality.
By means of a specially-built machine, I am going to present a
series of points (tactile SS) to the inside surface of your arm.
Your arm will rest in a foam rubber-covered tray and will be se-
cured in place by an elastic bandage. It is essential that you remain
still while your arm is in place on the arm rest. So that you will
be as comfortable as possible during the experiment, you are to lie
down on the air mattress and extend your arm onto the arm rest,
using the pillows to give your head support. You are to put cotton
in your ears and put on the ear muffs. Please keep your eyes
closed during the tactile presentations; you may, nonetheless look
around the room between trials. Do not, however, at any time,
look behind the black screen which shields the kinohapt from your
view.

I will give the signal, "Ready, " before each trial. At this signal,
you are to close your eyes and wait passively for the contacts to be

 

29

made on your arm. Approximately 2/3 of the time, a trial will
consist of two identical tactile presentations, and in the remainder
of cases, one presentation will be given per trial. I will tell you
ahead of time which of the two cases is forthcoming. When a trial
consists of two presentations, respond only to the second one if
possible. The first presentation will simply serve as a signal to
alert you for the second. Immediately after each trial, I want you
to tell me about or describe to me the impression or impressions
you had from the tactile SS. Tell me all you can about your im-
pressions in as detailed a manner as you feel necessary to insure
that your impressions are communicated to me.

The time interval from the end of one trial to the beginning of
the next is at least 45 sec. It will be longer if it takes me longer
than this to write down your response from the preceding trial.
Periodically, you will have short rest periods in which you will be
able to move your arm about and flex your fingers. [This was done
between conditions, or after every three trials.] If at any time your
arm feels strained or tired, please tell me and you can take your arm
out of the tray for a few minutes. [This was usually done mid-way
through a session, while E was changing and checking the drum
speed. ] —

The first two days of experimentation consist of orientation
trials, which will permit you to get oriented to the experiment and
the experimental conditions. During this period, it is particularly
important that you ask questions or make remarks concerning any
phase of the experiment about which you are in doubt. Are there any
questions?

The non-dominant arm of each 9 was used. Between each condition,
the positions of both needles were changed. 7 Spatial separations were in
error only as much as the ruler used to measure them was in error,
because the ruler was placed flush against the two needles. The needles
for the conditions of SS 2 1. 00 in. were placed mid-way between the elbow
and the wrist, and for progressively larger separations, the needles were
placed progressively closer to the elbow and the wrist. The perpendicular
distance from the needle tips to the arm was measured with calipers, and
care was taken to insure that the needles did not fall on hairs. (One 9
Shaved his arm periodically during the experiment because the hair on

his arm was so dense that this Situation was difficult to achieve.)

30

At the outset of Part II of the experiment, Os were instructed that
although most of the procedure was to remain unchanged, their method of
reporting was not. These additional instructions were read by 9 at the
beginning of the first experimental session (the instruction sheet was
called Sheet 1):

You are to use the diagrams given on Sheet 2 [see Appendix A]
to characterize the impressions you have from the various types of
stimuli. Study the diagrams carefully. Be sure to ask any questions
that come to mind concerning the diagrams and the impressions they
are intended to represent.

It is possible that you will not be able to find a diagram suit-
able for characterizing a given impression. . In this event, you are
to draw one that is appropriate on the sheet supplied you for your
responses [see Appendix B]. For all other impressions, i. e. , those
suitably represented by diagrams, you are simply to write down, on
this data sheet, the general class of the impressions, either A, B,
or C, corresponding to simultaneous, successive and movement
impressions, and the specific type of impression within a given
class, by writing 1, 2, 3, etc. , as the case may be, on your data
sheet. For example, if you have an impression which can be
characterized by this diagram: , you are to write A—3 on your
data sheet.

In addition to selecting or drawing a diagram to characterize
your impression, you are to further describe it by reporting on the
perceived nature of the departure of the stimulating object(s) from
the skin. The response categories are listed on Sheet 2, following
the diagrams, along with the key you are to use in making these
responses, e. g. ,. FF and SP.

You will receive 12 stimulus conditions per day with 3 trials
per condition. Your data sheet provides a line for each one of the
36 reSponses you will make per session. The column headings
indicate in what order you are to write the three components of each
response, e. g. , A-3-SP. If you need to draw a diagram, do so in
the blank space provided on the right side of the data sheet. Be sure
to label the diagram with the appropriate condition number and trial
letter. When you have finished categorizing a response, indicate
to me that you have done so.

After they read the instructions, 93 were then shown the slanted
writing tray and its use was explained. When 0 was in testing position, the

tray was placed in front of him so that he could readily see the diagrams

31

and could easily record his responses. (The set of diagrams and a data
sheet were tacked on the tray before the beginning of each experimental
session.)

Since it was found in the practice and experimental sessions, 'con-
trary to hypothesis, that apparent movement can occur in the absence of
offset of 83, i. e. at D = 5000 msec. , it was supposed that it would be more
meaningful and fruitful to consider time intervals, not from offset of S, to
onset of 52, but from onset to onset. (If one knew precisely when complete
adaptation to a stimulus of given duration took place, one could call this S
offset, and measure the temporal distance from this point to the onset of
52, but unfortunately complete adaptation time varies considerably, depend-
ing on Skin texture and condition, weight of S, etc.) Converting the time
intervals used in this study from the former to the latter measurement
scheme, one obtains, for D = 150 msec. ,7 TI = 0, 75, 150, 225, 300 and
450 msec. , for D = 300 msec. , T1 = 150, 225, 300, 375, 450 and 600 msec.
The TIS for D = 5000 msec. were, of necessity, initially defined from
onset to onset, and were 0, 75, 150, and 300 msec. In order to compare
durations at onset to onset TIS, then, it was necessary to supplement
these above TIS with the following additional conditions: at D = 150‘msec. ,
T1 = 375 and 600 msec., at D = 300 msec. , T1 = 0 and 75 msec. , and at
D = 5000 msec., T1 = 225, 375, 450, and 600 msec.

All of these supplementary conditions were presented except D =
300, T1 = 0 (which was not Since it was expected that 98 would experience
these conditions as simultaneous and/or single impressions and these
experiences were not particularly of interest) at all four of the major SSS,
i. e. at SS 2 1. 00, 2.00, 3.00, and 4.00 in., for a total of 28 additional S
conditions. These conditions were given on two successive days, 14
conditions per day, to the 4 _O_S who reported apparent movement in the
earlier sessions (one reported none in either the practice or experimental

sessions). The procedure maintained was precisely that used throughout

32

the earlier experimental sessions. Approximately 6 wks. to 2 mos.

 

separated these two supplementary experimental sessions from the earlier
six.

The purpose and the hypotheses of the experiment were briefly dis-
cussed with 95 at the end of their 14th session; the distinction between
on- and off-skin movement, both experiential and mechanistic, was
suggested in this discussion. Although it was feared that this discussion
might influence (_Ds' reports in the subsequent additional sessions, it was
hoped that since 6 wks. to 2 mos. had passed since the 14th sessions, Os
would not recall details of the discussion, or that if they did recall it, it
would have no bearing on their responses.

The results from experimental sessions 1-6 will be treated in the
initial portions of the following chapter, and subsequently, the data
obtained during sessions 7-8 will be presented. Until and unless other-
wise stated, the results reported in the succeeding chapter pertain to
conditions for which TI indicates offset-onset temporal separation between

SI and 52.

CHAPTER IV

RESULTS

Observer AC (female, age 37) reported no apparent movement
whatsoever throughout the course of the experiment. During the second
orientation session, she'exclaimedafter one presentation that, ."It seemed
like that moved but I just know it couldn't have; I must be cracking up.

I don't know what to believe is real anymore. " She was immediately

told by IE not to report what she thought S was, but to describe what her
experiences to S were as fully and accurately as she possibly could, no
matter how unusual and unreal they seemed. However, after this occasion,
AC never again mentioned movement except in reporting what she called
“radiating after-effects, " which she described as ”tingling going out in

all directions" from the point of contact after the stimulating objects were

 

experienced as withdrawn. It is not known, of course, whether she did
experience movement again and Simply was too embarrassed and ashamed
to admit that she had had such "crazy" experiences, or whether she did
not further experience tactual movement. At any rate, AC'S results will
not be considered henceforth in the presentation of the results.

The other 4 98 each reported several types of tactual apparent
movement. In addition to the 12 movement diagrams included on 93' key
(Appendix A), 8 other types of movement impressions were represented
by them with additional diagrams. These 8 were all variations of C11
and C12 impressions, that is, all represented off- Skin movement of one
sort or another. Some showed movement only part way between the two
end points, others showed one or both end points to be blunt (represented

by the hatched circle), some showed various combinations of movement

33

34

low and flat over the skin (C11) for part of the distance between the two
end points with bow movement (C12) over the remainder. On-skin move-
ments, then, were represented by diagrams Cl-lO and off-skin move-
ments by Cll-ZO.

Throughout this paper, movement experiences, when considered,
will be reported in terms of a) proportion of all types of movement
combined, b) prOportion of on? skin movement, and c) proportion of off-
skin movement, where the proportions are the relative frequencies for
the S condition(s) in question. (At a later time, analyses will be made
of the frequency Of different types of on- skin at the 4 SSS and 6 TIS; for
the present all types of on- skin and all types of off-skin movement are
considered collectively.) And unless otherwise stated, the results re-
ported are those obtained strictly from the experimental conditions
exclusive of the one-point and 5.00 in. S conditions.

The total, on- and off- Skin proportions of movement for OS singly
and combined at each of the three 5 durations are given in Table 1. As
can be seen, and as was indicated previously, movement was reported
for D = 5000 msec., contradicting hypothesis 5. The results relevant to
each of the 6 hypotheses will be presented in the order as were the
hypotheses, so that this matter will be elaborated further at the appropriate

time .

1. Relation of TI to 55. It was hypothesized that S conditions of

 

D = 150 and 300 msec. with high movement response probabilities were
those for which TI and SS were directly related, particularly those con-
ditions at the extreme TI and SS levels (with the exclusion of simultaneous
TI conditions). ’This hypothetical relation of TI and SS to proportion of
movement is expressed graphically in Fig. 2. . (It was expected that if TI
and/or SS were increased to a sufficiently great extreme, experiences of

movement would no longer occur, but just what constitutes sufficiently

35

great extremes was not known. T1 = 300 msec. and SS = 5. 00 in. con-

ditions will be expressly considered in this regard.)

Table 1. Proportion of On-skin, Off- skin and Total Movement Responses
at D = 150, 300, and 5000 msec.

 

 

 

 

D All Ds
9 150 300 5000 Combined
TT On .11 . 11 . 25 .15
Off .19 .15 . 04 .14
Total . 30 . 26 _ . 29 . 29
TN On . 53 .47 .46 .49
Off . 22 . 26 . 08 . 20
Total .75 .73 .54 .69
AlC On . 26 . 24 . 31 . 26
Off . ll .17 .12 .14
Total .37 .41 .43 .40
JR On .06 .15 .00 .08
Off . 08 . 22 . 08 .14
Total .14 . 37 . 08 . 22
Combined
(_Ds On . 24 . 24 . 26
Off .15 . 20 . 08
Total .39 .44 . 34

 

The obtained results for the 4 93 combined at TIS from -150 to 300
msec. and SSS from 1. 00 to 4. 00 in. for D = 150 and 300 msec. conditions
are presented in Fig. 3. , At T1 = -150 msec. only D = 300 msec. results
are included, because at D = 150 this TI constituted a simultaneous two-
point presentation for which it was expected that C_)s would make Class A
responses. Notice also that the results of the 5. 00 in. conditions are
presented.

Only at TI = 75, 150 and 300 msec. are the obtained proportions at

all similar to the predicted proportions. It would appear that SS is an

36

important variable in the determination of amount of movement only at

the larger TIS (at least for the SSS and TIS presented in this experiment).

2.. Relation of TI to D. It was expected that TI need not be inversely

 

related to D in order to maximize apparent movement; it was, in fact,
thought somewhat likely that amount of movement would be Similar for

both D : 150 and 300 msec. conditions at the various TIS. The obtained
results (for all (_)s and SSS combined) are presented in Fig. 4. The inverse
relation was, as expected, not evidenced, but the two curves bear only a
loose similarity. (The points on the curves at TI 2 -150 msec. should

not be compared, since they were not expected to be similar.)

3. On-skin movement as a function of TI and SS. The predicted

 

relative frequencies of on-skin movement at each combination of the 4
SSS and 6 TIS are shown in Fig. 5. The results obtained for the 4 Os
at D = 150 and 300 msec. conditions, Shown in Fig. 6, do not support this
prediction. Roughly speaking, only a rather gradual decrease in propor-
tion of on- skin movement as a function of T1 for a_l_l_ SSS was obtained.

If variations in the size of SS did not appreciably affect the amount
of on- skin movement, the quality of on- skin movement was greatly affected
by such variations. It was expected that the smaller the SS, the greater
would be the extent or completeness of the movement on the Skin, and the
larger the SS, the lesser would be the completeness. For example, it was
expected that at SS = l. 00 in. more full movement, continual on- skin move-
ment from point 1 to point 2, would be reported than at the other SSS, and
that inner movement, back and forth movement restricted to a small
circular area around the end points, would more likely occur at SS 2 4. 00
in. than at the other SSS. On- skin movement was classified according to
the following three decreasing levels of completeness: A) full movement,

represented by diagrams C8, 9, and 10 in the response key (Appendix A),

Proportion of Movement

Proportion of Movement

PrOportion of Movement

1.

.75—

00

 
 
  

 

1.00"
2.oo"—.——-——
.«-' 3.00n -

 

 

4. OO'L""'.‘.~o-s u-..

 

TI
Fig. 2. Theoretical Proportion of Movement as a Function of TI for

5521.00, 2.00, 3.00 and 4.00 in. 00..
.mw______

.00"——-. ——

...00" ............ ..

 

unbwwt—t

 

l

 

 

150* -75 o is‘ 150 360
T1 in msec. (offset S, to onset 52)

Fig. 3. Obtained Pro ortion of Movement as a Function of TI for SS —
100, 2, 00, .00, and 4. 00 in. at D— - 150 and 300 msec.

150 msec.

 

 

-150 -715 6 -' 75 150 grit)
T1 in msec. (offset S, to onset 52)
Fig. 4. Obtained Pro ortion of Movement as a Function of T1 for
Combined at = 150 and 300 msec. Conditions.

Proportion of On-skin Movement

1.

Proportion of On-Skin Movement

.751

00

‘.§-.
.’\‘“.-

38

1.00"
2.00" ———.._...._..
3.00" —— . _—

4. 00" m----..........

 

   
      

\
-...,...“.““ \
"."""--..“‘. \ . \ \
"‘-~...._‘... \ \
.ve ...... .‘..‘ . N§~

“.§.
‘9
§..'.Q..‘..‘
.\

 

TI

Fig. 5. Theoretical PrOportion of On-skin Movement as a Function of
TI for SS = 1.00, 2.00, 3.00, and 4.00 in.

1.00"
2.00" —————

3.00" -
N 4.00" .............. .....
5.00" C’)

 

 

 

~150* —75

 

150 360
TI in msec. (offset S, to onset 52)

o)—
‘1
U1

Fig. 6. Obtained PrOportion of On-skin Movement as a Function of TI
for SS = 1.00, 2.00, 3.00, and 4.00 in. at D = 150 and 300

msec . Conditions .

*Only S conditions of D = 300 msec. included.

39

B) end movement, partial movement between points 1 and 2, represented
by diagrams Cl, 2, 3, and 4, and C) inner movement, represented by
diagrams C5, 6, and 7. In Table 2 are presented the relative frequencies
of each of these classes of on- skin movement at each SS from 1. 00 to 4. 00
in. for all 95 and all two-point conditions presented in the initial 6
experimental sessions. The obtained relative frequencies for the 4 SSS
support amazingly well the expected relation. Full movement constituted
61% of on- skin movement at SS = 1.00 in. conditions, and decreased con-
tinually until at the 4. 00 in. conditions no full movement was reported.
End movement increased from 39-69% and inner movement increased from
0-31% as SS was increased from 1.00 to 4.00 in.

A Similar determination of relative frequencies of theSe three classes
of on- skin movement as a function of T1 was made. (Only D = 150 and 300
msec. conditions were included here, since TIS for D = 5000 were not
comparable to those for 150 and 300.) A summary of the results obtained
is presented in Table 3. Type of on- skin movement is, evidently, not
nearly as dependent on T1 as SS, although as might be expected, full move-
ment is not common at large TIS, and end movement is most common at
T1 = 300 msec.

Analyses comparable to the two preceding ones for off- skin move-
ment were not made since only three partial off- skin movement reSponseS

were reported in the entire study.

4. Off-Skin movement as a function of TI and SS. The theoretical

 

and obtained proportions of off- Skin movement responses are graphically
presented in Figs. 7 and 8, respectively. , The obtained results can be
seen to bear some similarity to the predicted results. The results ob-
tained indicate that at T1 = -150 to 75 msec. , SS does not noticeably in-
fluence proportion of off- skin movement, while at T1 = 150 and 300 msec.
it does so and generally in the manner predicted (SS = 3.00 in. , TI =

300 msec. conditions excepted).

40

Table 2. Relative Frequencies of the Three Types of On- skin Movement
at SS 21.00 to 4.00 in.

 

 

 

Class of On-Skin SS

Movement and

Typical Member 1.00 2.00 3.00 4.00
Full .61 .38 .22 .00
o-—>o
End . 39 .61 .67 .69
o—9-—>O
Inner .00 .01 .11 .31

@@

 

Table 3. Relative Frequencies of the Three Types of On-skin Movement
at TI(offset S, to onset 52) = -150 to 300 msec.

 

 

 

Class of On-skin TI

Movement and _

Typical Member -150 .- {-75 , 0'.) ‘75 150 300
Full . 23 .46 . 26 . 26 .05 .00
o-—->o
End .70 .49 .70 . 58 . 95 .78
o—-> —>o
Inner .07 .05 .04 .16 .00 .22

OO

 

Proportion of Off-skin Movement

Proportion of Off—Skin Movement

1.

 

41

 

1. 00..
2.00”—————_— .O..o'

3.00"______ .'."o ' /
4. oo .. fl,» /

 

 

 

TI

Fig. 7. Theoretical PrOportion of Off-Skin Movement as a Function of T1
for SS =1.00, 2.00, 3.00, and 4.00 in.

 

 

00
1

1. 00"-
2. 00"... __ __ __

'75“ 3.00" .
4. OO""'¢¢“OO~QOOOOO
5. 00" (°)

. 50 4 .O..........00

 

 

J
-150* -75 0 75 150 300

T1 in msec. (offset S, to onset 52)

Fig. 8. Obtained Proportion of Off-skin Movement as a Function of TI
for SS = 1.00, 2.00, 3.00, and 4.00 in. at D = 150 and 300

msec . Conditions .

*Only S conditions of D = 300 msec. included

42

Since a meaningful distinction between on- and off-skin movement
was and is considered by the author crucial to an understanding of appar-
ent tactual movement in general, it therefore, would afford a basis for
new contributions in the area of apparent movement. , It would be well,
then, to further examine the results obtained regarding on— and off- skin
movement.

Except at the largest time intervals, amount of movement of either
variety was found to depend primarily on TI, with differences in SS
contributing little to the total effect. Therefore, a consideration of
amount of movement as a function strictly of TI will now be undertaken.
Because they provide further insights into the identification of conditions
associated with reports of on- and/or off- skin movements, the following
figures are presented: 1) Fig. 9, Proportion of Total, On- and Off-Skin
Movement of All Os Combined, at D = 150 msec. , as a Function of TI;

2) Fig. 10, Proportion of Total Movement for Each 9, at D = 150 msec. ,
as a Function of TI; 3) Fig. 11, Proportion of On- skin Movement for Each
_O_, at D: 150 msec. , as a Function of TI; 4) Fig. 12, Proportion of Off-
skin Movement for Each 9, at D = 150 msec. , as a Function of TI;

5) Figs. 13-16, identical in nature to Figs. 9-12, except that D = 300
instead of 150 msec. As can be seen in Figs. 9 and 13, the on.-- skin curves
for the two durations are very similar (except at T1 = -150, of course),
while the off- skin curves are not so. And regularity among 93 is seen
only for off-skin curves for D = 150 msec. , thus suggesting that the two
types of movement are a product of or arise from dissimilar mechanisms,
and that the difference between these two durations does, after all, have
significant bearing on the reports of apparent movement.

Another interesting way of examining the on- and off- Skin data is
the following: Hypotheses 3 and 4 of the study state that amount of on-
skin movement varies with TI (and SS) and off- skin movement directly

with TI (and SS). These hypotheses might otherwise have been stated that

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45

if movement occurs at successively shorter TIS the more likely it is

to be on-skin movement, and if at longer TIS, off- skin movement.
Presented in Fig. 17 are the obtained conditional proportions of on- skin
movement for conditions of D = 150 and 300 msec. , separately and com-
bined. (The conditional off- Skin proportions are, of course, 1 minus on-
skin proportions.) Only at TI = 0 is there a departure from the expected
results.

The amount of movement obtained at the various SSS is also of
interest in that the proportion of on- Skin movement showed a different
relation to SS than did off— Skin movement. . In Fig. 18, on- and off-
movement obtained as a function strictly of SS is graphed for D = 150 and
300 msec. ~ For both durations, off-Skin movement increased very slightly
as a function of SS, while incidence of on- Skin movement was relatively
the same across SS except for peaks at 3.00 in. for D = 150 and 2.00 in.
for D = 300 msec. conditions. All 4 curves are highly similar though.
The on- Skin curves for individual 98 (not shown) were all similar; the off-
skin curves, however, were of two types; one pair was relatively flat and

another increased as a function of SS.

5. Apparent movement in the absence of S offset: D = 5000 msec.

 

conditions. It was predicted that no movement would occur with these S

 

conditions. Though, of course, Ss of D = 5000 msec. eventually ceased,

it was not until after adaptation had taken place so thoroughly that 95
almost never experienced pickup when it finally occurred, in fact, 93
usually began to respond before S offset and they almost never realized they
had done so. The on- and off- skinmovement results for individual Os

are presented in Figs. 19 and 20, respectively. . It is interesting to note
that individual off- skin curves, like those for 9D = 150 msec. bear certain
Similarities to each other and they are also somewhat similar in shape

to the D = 150 msec. off-skin curves.

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47

6. Experience of pickup of stimulating objects. It was predicted

 

that in order for off- Skin movement to occur, experience of pickup or
departure of the stimulating object must also occur. To test this hypothe-
sis, the proportion of movement responses occurring in conjunction with
reports of pickup were found for each 9. All three trials for each con—
dition were not counted in the determination of these proportions, since
they probably were not independent. Instead, the mode response regarding
both presence or absence of off- skin movement and pickup and non-pickup
for each condition was found. Os occasiOnallyreported different pickup
experiences for the two styli; when this was the case the experience report-
ed for the first stylus was used in this analysis since it was of principal
importance. Results of the 56 conditions exclusive of the one-point,
Simultaneous, and 5. 00 in. S conditions were used in this analysis.

The proportions of off- skin movement responses accompanied by the
experience of pickup (either fast or Slow) were . 57, . 86, . 78 and 1.00

for TT,. TN, AltC, and JR, respectively. The combined proportion was
.87. In testing the null hypothesis that p: .5, a t = 7.11, df = 41, p < .01,
was obtained, so the proportion of movement with pickup was significantly
greater than . 5 or chance. The same test was made for on- Skin move-
ment. The proportions of on-skin movement with pickup. were . 52, . 80,

. 78, and 1.00 for TT, TN, AlC, and JR, respectively, and the combined
p = . 75. A p = . 75 was also significantly greater than . 5 (t = 4.46,

df = 59, p < . 01) so that both on- and off- skin movement occurred a sig-
nificantly greater number of times with experience of pickup than would be
expected by change. Experience of pickup may, then, enhance the prob-
ability of the occurrence of apparent tactual movement. It is certainly

not a sufficient condition for its occurrence; of the 53 cases in which 'the

4 98 reported experience of pickup, 47% of these were no_t accompanied

by reports of movement.

48

One—point stimulations. 03' reports of pickup for the one-point

 

stimulations are summarized in Table 4. Since the shorter the D, the
greater the experience of pickup, one might expect that less movement
would occur at the longer Ds. Reference to Table 1 indicates that this
supposition is not correct. (Table 1 gives movement for two—point con-
ditions, of course; only two or three Spurious reports of movement were
obtained with one-point SS. Frequency of experience of pickup for two-
point 55 was approximately the same for D = 150 and 300, and was much
less for D = 5000 msec. [Thirty- five, 39 and 7 were the respective fre-
quencies]. (25 TN and JR do show a drop in apparent movement at D =
5000 msec. , but it must be remembered that the TIS for D = 5000 were
not altogether comparable to those of the other two durations, and there-
fore, it may be that amount of movement at D = 5000 msec. cannot be

justifiably compared with amounts at D = 150 and 300 msec.).

Table 4. Perceived Nature of the Departure of the Stimulating Object
for One-point SS of D = 150, 300 and 5000 msec.

 

Nature of Departure
(Percent Reported)

 

D FP SP NP ?
150 42 25 29 4
300 12 33 29 25
5000 12 4 71 12

 

Verbal responses. The group verbal response curves for total,

 

on-skin, and off- skin proportions of movement for D = 150, 300 and
5000 msec. were highly Similar in shapes to their respective experimental
curves. There was, however, more movement reported during the
experimental sessions, especially off-skin movement, for D = 150 and 300

msec. There was 63% agreement for general classification of

49

impressions, i. e., A, B, and C (Appendix A) between 98' verbal

(practice sessions) and multiple choice (experimental sessions) responses.

Results of conditions in which T1 = onset S, to onset Sz interval.

 

Each of the 4 95 who received the additional 28 conditions reported that

he or she had no trouble resuming experimentation without additional
practice trials, even after the long interim between experimental sessions
6 and 7. None had any questions about the use of the response key, and
only the usual questions about the recording of their responses were asked.
The results of_a_l_1 two-point S conditions with TIS indicative of onset to
onset intervals are presented in Figs. 21-28. (For D = 300 msec. , TI =

0 msec. conditions, the proportions were assumed to be . 00 and were so
represented, but since no such conditions were presented to _O_S, these

are only theoretical proportions.) These results, recall, were obtained
from the original experimental session conditions after the TIS were con-
verted from offset-onset to onset-onset temporal separations and from

the 28 supplementary onset to onset conditions. By combining the two sets
of results, it was possible to compare duration curves at 8 onset-onset
TIs, ranging from 0 to 600 msec.

In Fig. 21, the proportions of on- skin movement for all 98 com-
bined as a function of T1, for each of the three Separate durations, are
presented. As can be seen, with TI given in terms of onset-onset, the
proportion of on- Skin movement is very nearly the same across TI for
the three S durations. It would appear that amount of on- skin movement
for 95 combined was not appreciably altered by variations in S duration.
After T1 = O (simultaniety), a general decrease in on- skin movement as
a function of TI is seen for all three durations. Although a general in-
crease in movement occurred up to about TI = 375 for all DS as a
function of TI (Fig. ‘22), the off-skin curves are less similar than the

on- Skin curves. From T1 = 300 to 600 msec. , the D = 150 and 5000 msec.

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52

curves are quite Similar in shape, while the D = 300 msec. curve is
rather different from the former two.

It is imperative to note here that none of the TIS from 300 to 600
for D = 300 were presented in the two supplementary experimental sessions,
while for D = 150, two of them were presented (and these were the only
two D = 150 conditions presented at the later time) and for D = 5000, 3 of
the 4 supplementary TIS were in this range. Since, as stated before, the
purpose of the experiment was discussed with Os at the conclusion of their
14 original session, and particularly since on- and off- skin movement was
specifically discussed, it unfortunately, appears likely that _O_s' frame of
reference had changed or shifted from the early to the later sessions or
that they did not have _a_r_1_y workable frame of reference for making judge-
ments to the last 28 conditions. (For the first 73 conditions they did,
presumably, because they had already encountered all of these 73 con-
ditions in the practice sessions.) It appears that, perhaps because of
suggestibility, 98 were more prone to experience movement in the last
two experimental sessions than in the first six, and since off- skin move-
ment is believed to be far more dependent on broad cognitive references
than is on- skin movement, it is particularly with off— skin move-
ment that the increase is seen. A specific case in point is the following:
The D = 150 on- and off- skin curves of Figs. 21 and 22 are broken down
by (2 and these resulting individual _O_ curves for D = 150 are presented in
Figs. 23 and 24. Upon examination of the off- skin curves (Fig. 25) the
male 9 curves, i. e. those of TT, TN, and AlC, it can be seen that the
proportions at both T1 = 375 and 600 exceeds that obtained at T1 = 450.
It is curious, indeed, that it was T15 of 375 and 600, for D = 150 con-
ditions which were presented in the follow-up sessions. The off-skin
curves for TT and TN at D = 5000 (Fig. 28) Show the same effect. While
it is possible that these increased proportions are representative of the

"true" state of affairs at these TIS, I do not believe it likely.

53

The obtained proportions of on- and off-skin movement for individual
95 for D = 300 msec. conditions are presented in Figs. 25 and 26, and
for D = 5000 msec. conditions, in Figs. 27 and 28. Only the off-skin
curves at D = 150 are consistent in shape for the 4 OS; and it is inter-
esting to note here that JR'S curve is the most atypical of the four, and
JR is the only female of the four. (This was also true in comparing other
sets of individual curves, for example as seen in Fig. 19.)

In view of the aforementioned effect which seems to have been mania
fest during the two supplementary sessions, I believe it is unwise to
further combine the results from these sessions with those of the previous
sessions. However, it is possible to examine, separately, the results
obtained from the two supplementary sessions, for although the absolute
amount of movement reported was greater (at least for 3 (_)_S) than the
previous sessions, within these two sessions the relative prOportions of
movement obtained for the various S conditions can be contrasted. It was
especially hoped that an examination of these results would suggest more
completely in what manner SS is related to frequency of on- and off- skin
movement. The results of the 7 D and TI combinations at each of the 4
SSS for the 4 95 combined are graphically presented in Fig. 29. As be“
fore, the proportion of on-skin movement remained fairly constant as SS
was increased from 1. 00 to 4.00 in. , while off- skin movement increased,
rather abruptly at 2.00 in. and to a lesser extent at 4. 00 in. Only at
SS 2 1. 00 is the proportion of on-skin movement greatly different from

proportion of off- Skin movement, however.

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CHAPTER V

DISCUSSION

While it is evident from the presentation of results that only quali-
fied support for some of the experimental hypotheses, specifically
hypotheses 1, 3, and 4, was obtained it is, nevertheless, possible to
identify several important relations pertaining to features of apparent
tactual movement phenomena with which these hypotheses were concerned.
It is well to emphasize again that these phenomena often seem unreal and
transitory, making meaningful response criteria difficult to achieve since
referents for these experiences are lacking, and that they are highly
subject to set, attitude and day-by-day variations in mood, comfort,
fatigue, boredom and physical state. Therefore, inter- and intra-
observer variations are to be expected, and thus it is difficult for possible
lawful relations between S conditions and movement experiences to be
made manifest. All 98 at various occasions during the course of the
experiment expressed concern about the accuracy of their responses
for reasons variously given as inability to concentrate, tiredness, and
vague feelings of uncertainty about their experiences. Suggestions for
controlling for the effects of such subjective factors are made at the con-
clusion of this chapter.

The results pertaining to hypotheses l, 3, and 4 as well as of 2,

5, and 6 will be discussed in order, after which the results in general,
along with alternative hypotheses and suggestions and implications for

further research, will be discussed.

Hypothesis 1. As shown in Fig. 3, only at the large time intervals

 

does SS appear to function jointly with T1 in the determination of amount

55

56

of apparent movement in the manner predicted. At the shorter intervals,
1. e. , from TI = -150 to 75, amount of movement did not vary appreciably
for the 4 SSS, but for each SS declined as a function of TI (except at

SS = 1. 00,. TI 2 -150). . As will be evident in the discussions of on- and
off- skin movement, this was due to the fact that off— skin movement, which
occurred predominately at the larger TIS as predicted, was dependent on
the magnitude of both TI and SS, while amount of on- skin movement, which,
as predicted, was inversely related to T1, was not but was dependent only
on T1. By combining on- and off- skin movement? forthe purposes of
analyzing total amount of movement as a function of SS, two different rela-
tions of 5 conditions to frequency of movement are then operative in the
resultant combined data. So as not to obscure theitwo different relations,
it would be well to consider on- and off— skin movement only separately and

not combined.

Hypothesis 2. The results obtained are in accord with the hypothesis

 

that D need not be inversely related to TI in order to obtain maximal
apparent movement (cf. Figs. 4, 7, 13, 21 and 22). This is particularly
true of on-skin movement as shown in Fig. 21.. The relations between on-
skin movement and T1 are very nearly the same for the three durations
used in this study, including D = 5000 msec. . FOr all Ds, the highest
proportion of on- skin movement was obtained with TI (onset S,-onset $2) =
75 msec. S conditions, and a decreasing proportion of on- skin mOvement
was obtained thereafter. These results are in agreement with those
reported by some of the early researchers. Burtt (1917) reported maximal
movement (of all types) at T1 = 75, Whitchurch (1921) reported the greatest
amount of on-skin movement (although she did not call it that) between 50
and 100 msec. , and Hulin (1927) found that all types of movement com-
bined and full movement alone (diagram C 8 in the key. used in the present
study, of. Appendix A) occurred most frequently at T1 (offset-onset) =

-75 which is equivalent to T1 (onset-onset) = 75 sinCe Hulin used only

57

D = 150 msec. conditions. In each of these early reports, movement
also decreased continually as a function of TI after the peak frequency
was reached.

Because only for onset-onset TI conditions can all three durations
be compared across TI, it is difficult to determine from the results of
‘ the present study, how off- Skin movement, for all three durations, is
related to T1, due to the inadvisability of combining the supplementary
data with the initial experimental data, especially with regard to off-skin
movement. (It Should also be recalled that two presentations of S con-
ditions of D = 150 and 300 msec. were presented per trial and only one
of D = 5000 msec. And the inter-trial intervals for D = 150 msec. were
one—half those for D = 300 conditions since the same pawls were used to

present conditions of both these durations, which necessitated that for D =

 

150 msec. conditions the drum speed be twice that of the speed for D = 5
300 msec. conditions. Consequently, it is difficult to make positive state-
ments regarding the relation of S duration to occurrence of movement.)
The off— skin results of this study, given in Fig. 22, indicate that only
conditions of D = 150 and 5000 msec. , and not of D = 300 msec. , are
similarly related to incidence of off- skin movement. However, it remains
for future experimentation to adequately answer the question of how S

duration is related to off- skin (and possibly on- skin) movement.

Hypothesis 3. . A comparison of Fig. 6 with. Fig. 5, which contain,

 

respectively, the obtained and theoretical proportions of on-skin move-
ment as a function of T1 with SS as the parameter, suggests only that
there is a general decline in on- skin movement as a function of TI for

all SS. Only the proportions of on- skinmovement obtained for the 4 SSS
at T1 = -150 msec. are greatly different, but even then, not in the manner
predicted. . In any event, it appears that the prime factor in the determin-

ation of amount of on - skin movement is the temporal interval between

58

the two SS, at least for the conditions used in this study. However, it may
be that the SSS used in this study were not varied over a wide enough range
to permit the possible effects of SS on incidence of on- skin movement to

be made evident. Possibly S conditions with SS = . 25, 2. 50, 5. 00 and

10. 00 in. would produce differing amounts of on- skin movement at the
various TIS. Since extent or completeness of on-skin movement was found
to be greatly related to the magnitude of SS and in such a way that it
declined as a function of SS, it is expected that if SS were continually in-
creased beyond 4. 00 in. , at some point the incidence of on- skin movement
would begin to decline. . And it would be interesting to determine whether
amount of on- skin movement would increase for SSS decreasing in magni-
tude from 1.00 in.

An interesting feature of on- skin movement noted in the results
obtained is the following: It was supposed before the experiment com-
menced that differences in the non-neural features of 95' skin would be a
relevant factor in the determination of on- skin movement, since it is the
movement of this portion of the skin tissue which in turn activates the sur—
rounding neural tissue, which then eventuates in a tactual experience if
the rate and amount of movement was sufficiently great. (Bartley gives a
clear account of the relative contributions of the two types of tissue in his

Principles of Perception, 1958, p. 361.) Since on- Skin movement was

 

thought to be heavily dependent on neural activity and off- skin on visual
imagery, it, then, was expected that only occurrence of on- skin move-
ment would be influenced by skin quality. . It was hoped that by including
both males and females in the study, these possible effects would be, in
part at least, controlled for since by including both sexes it was felt that

a systematic biasing of the on-skin results would not then occur. However,
since one female was removed, only one remained, along with the three
male 93 whose data were analyzed. It might, then, be fruitful to examine

the frequency of on- skin movement reported by the various OS.

59

By reference to Table 1, one can see that prOportions of on- skin
movement (for all BS combined) varied greatly among 95, with the follow-
ing proportions obtained: TN = .49, A1C = .26, TT = . 15, and JR = .08.
(Note also that the amount of off-skin movement was the same for three
Os, 6% higher for the fourth.) If I were to rate these 4 93 as to their
firmness or lack of pliability of skin tissue, I would rank them precisely
in this order. The implication is, in other words, that it may be that
degree of pliability of skin texture does influence amount of on-skin move-
ment. The less pliable the skin, the greater the resistance it would offer
to the stimulating object and the greater would be the impact of the object.
Possibly, then, the greater the impact and, therefore, the greater the
volume of tissue moved, the greater the likelihood of on- skin movement.
(Nafe and Wagoner (1941b) stated that they thought variations in skin
texture would influence rate and amount of movement in this way, but they
did not systematically vary skin texture nor did they elaborate further.
They used 2 _O_S, and although their sex was not reported, at least one
was male, since the principal author served as 9.) This supposition
might, then, account for the consistently dissimilar on- skin results among
_O_S at all durations (cf- Figs. 11, 15, and 19) despite the fact that the
off-skin results for identical S conditions (except those of D = 300 msec.)
are not dissimilar (cf. Figs. 12 and 20).

To further investigate this suppo’sition, the author served as _O_ on
5 successive days, each day with a different skin treatment applied to the
tested forearm. (Prior to this testing, the author had served as» 9 for
approximately two weeks, six hours per week, so was a practiced 9.)
Eight conditions were chosen semi-randomly from the original D = 150 and
300 msec. two - point stimulations, exclusive of 5. 00 in. and simul-
taneous conditions, by another 12.9 was not aware of which 8 conditions
were chosen until the end of the fifth session, except that E was told to be

sure and include some conditions with overlapping stimulations since these

60

are particularly conducive of on-Skin movement and to choose all other
conditions randomly. Prior to experimentation on the first day, an ice
pack was applied to (_D_' 8 arm, and on the second day a 100 W. lamp was
placed on the arm, in each case until the applications became quite un-
pleasant. (This was done to test the hypothesis that more movement
would occur with the heated than with the chilled arm.) On day 3, facial
cleansing cream, which is quite oily and can be worked into the skin,

was liberally applied to the arm three hours before testing. It was sup-
posed, of course, that by so doing, the pliability of 9's skin would be
increased. Although it was difficult to achieve a skin condition of low
pliability since C_), being a female and never engaged in extreme physical
activity, had rather pliable skin to begin with, but it was found that by
scouring the arm several times before testing with a gritty scouring
powder, the skin became much more taut and rigid (probably because of
its drying out), and, therefore, less pliable. Testing after scouring was
done on the 4th day, and on the 5th day, 9 was tested under normal skin
conditions. The proportions of on- skin movement obtained for the 5 days
were, in order, .14, .25, .21, .33, and .29. It is, of course, impossible,
to ascertain whether these variations were the usual day-by-day variations
either partly or‘ completely or whether they were truly the result of the
variations in skin texture, but they are in the predicted directions.

There was 1.1% more on-skin movement with the hot compared to the cold
condition and 12% more movement with the less pliable than the pliable

condition.

.. Hypothesis 4. Fairly good support was obtained for hypothesis 4,

 

as can be seen by contrasting Fig. 8 with Fig. 7. This was true of the
results of the D = 150 and 300 msec. conditions combined and for the
individual 9 results for D = 150 msec. (Fig. 12), but not for the individual

9 results for D = 300 msec. (Fig. 16). Just why there was consistency

61

of off- skin results among 95 at D = 150 (and for D = 5000 msec. also,
cf. Fig. 20) and not at D = 300 is not clear. The combined results for
93 at D = 150 and 300 msec. conditions, Shown in Fig. 8, do suggest as
predicted that "time and room" is needed to allow for the inference of
movement through the air to occur, and that the more of each, the more
likely is off- skin movement to occur, at least for the conditions used.
The limiting TI and SS conditions are not suggested in this study since,
apparently, not extreme enough conditions were included in the range of
TI and SS values used. The proportion of movement at SS 2 5. 00 in. is
considerably less than at SS 2 4.00 in. for TI = 300 msec. , but it is
greater than at S = 3. 00 (which, in itself, is an aberration unaccounted
for) so it is difficult to say whether an SS = 5.00 in. is "too great" so
that the inference of off- skin movement is difficult to make. (Benussi
(1917) and Hulin (1927) reported some bow movement at $53 up to 20 cm.
and 150 mm. , respectively, and TIS (onset S, to onset 5;) up to 620 and

450 msec. , respectively.)

Hypothesis 5. It is believed that the results of this study unquestion-

 

ably indicate that, in contradiction to hypothesis 5, apparent tactual move-

ment of the off-skin and on- skin variety can occur in the absence of S

 

offset. (In the phenomenal sense, S ceases, but no re-stimulation of the
skin occurs until after 5 sec. and even then it often does not occur, so
that an immediate experience of the physical S offset is not possible.)

It is necessary, therefore, in future experimentation to consider onset-
onset TIS when S conditions are used which are of durations such that
complete adaptation takes place while the stimulating objects are still in
contact with the skin. One could reasonably concern oneself with either
or both onset-onset or offset-onset TIs when experimenting with S con-
ditions short enough to preclude adaptation, since these conditions

stimulate continually throughout the duration of S and at S offset.

62

(Offset S, to onset Sz TIS would indicate how temporally far apart 5; is
from the last effective presence of 8,.) If both duration extremes are to
be presented, as in this study, and it is desired to compare the results

of all durations, then TI must be defined in terms of onset to onset.

Hypothesis 6. Off— skin experiences occurred a significantly greater

 

number of times when pick-up was also experienced thanwhen it was not,
as was predicted. This was a reasonable prediction in view of the fact
that experience of off- skin movement was considered to depend on a visual
image of one stimulating object picking up, moving over and touching
down again. It is not, however, reasonable that experiences of on- skin
movement were also associated, to a significant extent, with experiences
of pick-up. This apparent paradox bothered 95 too, because during the
experimental sessions, in which they were asked to indicate their pick-up
impressions, all of them at one time or another stated to the effect that
they couldn't understand it, but it (the first stimulating object) seemed to
hit with a sharp, concentrated impact and then simultaneously. it picked
up and moved across the skin toward the second point of impact. (93 also
mentioned somewhat less frequently, a similar effect with D = 5000 msec.
conditions. The stimulating objects were felt to leave but were still felt
to be present at the same time; the experience of their presence then
gradually diminished, usually after 2 or 3 sec.).

It is not certain, since experience of pick-up. was associated with
on-skin movement as well as off-skin movement, just why experiences
of movement were accompanied by experiences of pick-up at all. Perhaps
on-Skin movement is also dependent, to some extent, on visual imagery.
The experience of off- Skin movement is one of visualizing an. "up and over"
the skin path of the first stimulating object. Perhaps on-skin movement
occurs from the visualization of an "up and across or on" the skin path.

The latter visualization is not totally illogical, since it would be possible

63

to make the first stylus follow such a path. (The stylus, by depressing
the skin when it falls, comes to rest in this depression. It could lift
out of this depression, re-forming the skin, and then be dragged lightly
over the surface of the skin.) It may be, however, that movement re-
sponses and pick-up responses coincided as they did because they were
simply two ways of describing the same experiences. Or perhaps the
coincidence was fortuitous.

The results obtained support the view held by the author that on- Skin
and off- skin movements are generally aroused by different S conditions,
and hence the belief that a thorough, meaningful analysis of apparent
tactual movement must embody a distinction between these two types of
movement is supported. The S conditions which have high on- skin re-

sponse probabilities have low off— skin probabilities, and vice versa-

 

The likelihood of occurrence of both types of movement is most heavily
dependent on the time interval between S, and 52. On-skin movement most
likely occurs at very short TIS, and generally decreases as T1 is increased,
while off- skin movement occurs infrequently at short TIS and frequently
at long TIS. Apparently size of SS is relevant to amount of off- skin but
not of on- skin movement, at least for the S values used in this study.
It does have definite relevance to the completeness of on-skin movement,
however. This was not true for off-skin movement, since a large pro—
portion of off- skin movement responses were C12 responses at all SSS.
The relevance of variations in S duration to either on- of off- Skin
movement is not apparent. . If variations in D are important, they are
probably more important for off- skin than on- skin movement.
It was hOped that the results obtained would be such that the involve-
ment of different mechanisms for on- skin and off- skin movement would
be clearly indicated. It was supposed that end organ activity was respons-
ible for on-skin movement and visual imagery for off- skin movement. On

the basis of the results of this study, there is no reason to question the

64

latter supposition, but there is some doubt about the former. How does
one account for the fact that on- skin as well as off- skin movement occurred
more frequently with experiences of pick-up than without such experiences
without implying that visual imagery also plays a role in experiences of
movement on the skin?

However, the qualitative differences in on- skin movement as a
function of SS can be interpreted as strong support for the notion that
movement on the skin .1: determined by the combined effects on the end
organs produced by two SS occurring in close temporal and Spatial contiguity.
As has been made clear, it is movement of the skin which must necessarily
occur if a tactile impression is to be aroused. It is obvious that when an
object falls into the Skin, tissue is displaced (depressed) directly under the
object, and that the tissue surrounding the locus of stimulation, though to
a lesser extent, is also diSplaced, the amount depending, among other
things, on the weight of the stimulating object and the resistance offered by
the tissue (as Nafe and Wagoner (1941) suggested). The closer the tissue
is to the S object, the more it will be displaced and the sooner it will be
displaced. And recall that Nafe and Wagoner found that movement p_e_r_ is,
while necessary, is not sufficient for arousing tactile sensations, but it
must be movement greater than or equal to a certain rate and amount.

A tiny stylus falling into the skin is experienced as a tiny, discrete
point, then, because sufficient movement occurs only at the point of con-
tact; the movement in the surrounding tissue does not incite experiences
because it is not sufficiently great. Now consider dropping 3‘19. styli onto
the skin in close temporal and spatial succession; the impacts of the two
styli would both contribute to the displacement of the tissue intervening
between the two points of contact, so that the resultant effect would be that
the combined rate and amount of displacement between the two styli would
then be made sufficiently great to arouse a tactile impression. (In their

verbal responses, 95 frequently mentioned, for very short TI and SS

65

conditions, experiencing a bar or wire diagonally falling or being placed
on the skin, and sometimes these seemed to have knobs at the ends.)
Obviously, the shorter the SS and T1, the greater the amount of common-
ality of diSplaced tissue and therefore, the greater the likelihood of the
arousal of tactile impressions between the two stimulated loci. Experience
of on- skin movement occurs because the Spread of movement of S, occurs
first, is enhanced by 52 following closely and quickly, and consequently
S, seems to move toward 8;. S, seems to move toward S, since it occurs
first and becomes the dominant of the two. This domination due to
primacy might be overcome by making 52 sufficiently more intense than
S,, in which case the direction of movement would be reversed. This
effect, called delta movement, has been produced visually and auditorially.
It would be extremely interesting to know whether it could also be pro-
duced tactually.

This conceptualization of the arousal of on- skin skin movement
accounts for the on- skin results obtained in this study extremely well.
It accounts for the decrement in amount of On- skin movement as a function
of TI, and forthe dependence of its completeness upon SS (and to a lesser
extent, TI). The conceptualization would also account for the similarities
in amount of on- skin movement for the three durations used. Since the
movement produced by the styli begins to subside rapidly, the critical
rate is quickly past and so it does not matter how long the styli remains
on the skin as long as they are not again retracted and dropped.

To make the conceptualization of the mechanism of on- skin move-
ment complete, two additional factors must be considered. First of all,
it is sometimes the case that the apparent effects produced by the con-
? tiguity of the two 55 are not perceived to move; instead, more than two
points or bounces (usually 3 or 4) all of which occur in a straight line from
point 1 to point 2, are perceived, but as stationary. Apparent effects of

this type, represented by diagrams B8-ll in the response key, were

66

reported by Os in this study, particularly by JR. Such effects Should be
taken into account here; although not movement phenomena, they are

phenomena pertaining to the connectedness of S, and 52. In Figs. 30, 31,

 

and 32 (cf. p. 54 ) are presented the prOportions of on-Skin movement
and apparent bouncing responses for each 9 .‘for D = 150, 300, and 5000
msec. , reSpectively. With the addition of the bouncing responses, inter-
observer variations for on-skin phenomena are reduced at each duration
(Figs. 11, 15, and 19 contain individual curves for on- skin movement
alone), although the individual curves at D = 300 msec. are still not greatly
Similar. This would suggest that bouncing is just another manifestation
of on- skin apparent effects, and so ought to be included with on- skin move-
ment analyses. One might consider a continuum of connectedness as going,
from low to high degree, from bouncing, to inner, to end, to full move-
ment. The fact that JR had such a high relative proportion of bouncing
experiences can be accounted for in the same manner as was the fact that
she reported a lesser amount of on-skin movement than the other Os,
i. e. , by the greater pliability of her skin. The total number of bounces
reported by OS to the original two-point experimental conditions, in order
of their supposed lack of pliability (from high to low), were TN, 6, AlC,
4, TT, 25, and JR, 37.

An additional factor which must be considered obtains from the
recent work of von Béke’sy (1955, 1957, 1959), and Schmid (1961).
They were concerned with traveling waves upOn the skin and the Signifi-
cance of these on tactile localization and inhibition. Von Békésy found
that a mechanically induced wave initiated at point A was experienced only
at point A, even when the wave traveled for several cm. . (In attempting to
accountfor such precise tactile localization he stated that, ". . . the
maximum of the vibration amplitudes is always directly under the tip of
the vibrator, and this is the reason why the sensation is localized mainly

under the vibrator.” (1959, p. 5). This does not indicate sufficient

67

cognizance of the criticality of the rate and amount of tissue movement.)
The work of von Be’késy, Schmid, and others has some relevance to the
conceptualization of on- skin movement, because they reported that a
vibrating S, (or even a non-vibrating S,) can inhibit an 52 (generally they
mean raise the absolute threshold) or facilitate 82 (lower absolute threshold),
depending apparently on intensity and/or TI of-Ss- Von Békésy suggested
that an inhibitory mechanism improves localization. . Schmid, in review-
ing pertinent studies to date, stated that the data show that facilitation
only occurs with Simultaneous SS when their intensities are not greatly
diSprOportionate, and that inhibition occurs either when the intensities are
disproportionate or when TI is very small. (In her study, maximal
inhibition was obtained at TI 2 1-5 msec. and decreased and was scant at
TIS up to 40 msec. She used shocks for SS; S, was presented on the second
digit of the hand, 52 on either the third or fourth.) None of the conditions
necessary for facilitation or inhibition were presented in this study except
the simultaneous S conditions, and movement, of course, was not expected
or considered at those conditions. Nonetheless, in an account of on-skin
apparent effects and in future apparent tactual movement research, these
effects should be considered; qualifying statements about TIS and Is con-
ducive of inhibitory and facilitory effects on thresholds should be made
because apparent on-skin effects might be expected to be correspondingly
inhibited and facilitated, at such TIS and Is. . It is interesting to recall
here that Whitchurch (1921) and Hulin (1927), Who both presented some
TIS shorter than 75 msec. (from onset to onset), obtained maximal on-
skin movement at TI = 50-100 msec. and 75 msec. , respectively, and
gradually increasing amounts up to these maximums.

The fact that large variations among 93 in amount of on- skin but not
of off- skin movement was obtained also supports the supposition that
peripheral or end organ effects are involved in the arousal of on- skin

movement (and not in off- skin movement) because of the suSpected role

68

played by quality of skin tissue. This is in accord with the conceptualization
given, since styli would displace a greater volume of firm skin tissue than
pliable skin tissue. It would be interesting to determine whether on-skin
movement varies directly with muscular tonus by having 95, while being
tactually stimulated, squeeze a hand dynamometer with varying amounts of
effort. And the fact that amount of on- skin movement reported by the
author varied at all, much less varied in the predicted and accountable
directions, when skin conditions were externally manipulated is indicative
of the function of end organs in on- skin movement (if one is willing to
assume that the inter-day variations obtained were not merely of the order
one would normally obtain for a given 9, and that (_D, by having complete
knowledge of the experiment, did not bias the results in the expected
directions).

The results obtained in this study, though equivocal, are nonetheless
clearly rich in implications for future research in the area. It would be
exceedingly worth-while to test the hypothesis that the degree of plia-
bility or elasticity of skin tissue is related to the proportion of on- skin
movement experienced, and that the relation is an inverse one. In the
same vein, it would be expected that intensity of 5 would be related to
amount of on- skin movement. All other S variables held constant, it is
expected that the greater the intensity of $3, the greater would be the
amount of on- skin movement reported (at least as long as the increase in
I is identical for each 5). (Naturally I would have to be at least supra-
liminal and probably would have to be subliminal for pain.) And, as
already mentioned, it would be of great interest to know whether delta
movement can be obtained tactually by presenting S; with greater I than S,.

. It would be fruitful in future research to present more widely varied
SSS and TIS in order to establish whether SS can be a determinant of
amount of on- skin movement, what the limiting SSS and TIS are for both

on- skin and off- skin movement, and whether inhibitory on- skin effects

69

are manifested at the predicted S conditions. The possible contribution
of S duration to movement experiences might well be more thoroughly and
precisely examined. Inter-trial intervals and number of presentations
per trial should be the same for all those S conditions which are to be
compared.

A further investigation of the pick-up experiences associated with
experiences of both on-skin and off- skin movement might clarify the re-
lation or _significance of the one to the others. This clarification might be
made simpler by having 93 report when, in relation to their total impression
aroused by S, S seemed to be withdrawn, if withdrawal were experienced,
and what happens to S if pick-up is not experienced. It is not certain,
however, whether or not 95 could make such specific judgments because
even in this study, 95 reported occasionally that they had difficulty making
accurate reports about the perceived departure of S.

Since, as mentioned at the outset of this chapter, many factors can
Operate to enlarge inter- and intra-observer variations, and particularly
since large variations were obtained in this study, it would be very valuable,
though time-consuming, in future research to repeat all conditions a
number of times for each 9 on different days, .since in this manner effects
of such factors might be averaged out for each condition and, therefore,
more stable and representative responses might be obtained.

Finally, it is suggested that in order to achieve the greatest possible
understanding of apparent on- skin phenomena, ones point of departure in
future research should be more complete than simply a consideration of
on-skin apparent movement, but should be expanded to include non-moving,

on- skin apparent effects as well.

CHAPTER VI

SUMMARY AND CONCLUSIONS

In previous studies concerned with apparent tactual movement,
few contributions were made toward an understanding of the phenomena
in question and the mechanisms reSponsible for their arousal; instead,
the results obtained by the early workers in the area were contradictory
and ambiguous. A multitude of methodological and theoretical short-
comings were seen as the bases for this state of affairs. . The purpose of
the present study was, by circumventing these shortcomings, to achieve
such an understanding. It was believed that an adequate test of each of
the following hypotheses was requisite to any complete understanding of
apparent tactual movement:

1) Stimulus conditions which satisfy the direct relation of TI and
SS, particularly at the extreme TIS and SSS, are the conditions most
favorable for producing movement.

2) To secure maximum frequencies of apparent movement, it is
not necessary that conditions in which D is inversely related to T1 be used.

3) Frequency of on- skin movement is inversely related to TI and SS
jointly, 5 suggesting that temporal and possibly Spatial summation Of
neural activity from the two stimuli is necessary for the experience of
movement on the skin.

4) Frequency of off- skin movement is directly related to T1 and SS
jointly, ' indicating that "time and room" is needed to make it feaSible or
logical to obtain movement through the air.

5) Cessation of S must occur (apparently before adaptation is
completed) so that both S onset and S offset can be experienced in order

for apparent movement phenomena to occur.

70

71

6) An awareness of the departure of the stimulating objects from the
skin is necessary for the experience of off- skin movement.

Five 93, 3 males and 2 females (one of whom was not included in the
data analyses since she failed to report apparent tactual movement experi—
ences) were used in this study for one-hour periods on 14 separate days.

A Bartley kinohapt was used to present one- and two-point stimulations to
the volar surface of the forearm. A drum, revolving at constant speeds,
upon which pawls were secured was used to achieve the desired time inter-
vals (TIS) and durations (Ds) of SS. The styli of the kinohapt were released
by activation of the solenoids, which in turn were activated by microswitches
that were tripped by the pawls. The spatial separations between Ss (SSs)
were varied by moving the styli the appropriate distances apart. -

In S conditions presented in this study, TIS (from onset $1 to onset Sz)
ranged from 0-600 msec. , Ds were 150, 300 and 5000 msec. , and SSS
ranged from 1.00 to 5. 00 in. In the original study, 73 S conditions were
presented in semi-random orders to all _O_S; in part I of the original study,
which constituted the practice stage, all 73 conditions were presented to
which 9s were asked to verbally describe their experiences, and in part 11,
these conditions were again presented but C_)s in this case were instructed to
indicate their experiences by choosing disgrams, from a response key given
them, which represented their experiences (or by drawing any necessary
additional diagrams). A supplementary study was done 6 wks. -2 mos.
after the original, using those 95 who reported movement in the latter, in
which 28 additional S conditions were presented. 98 responded to these as
they did in part II of the original study. The data obtained in part I, for
various reasons, were not deemed suitable for analytical operations; the
data which were analyzed and upon which the following conclusions were
based, were obtained in part II of the original study and the supplementary

study, though primarily in the former.

72

It is concluded that:

a) While the obtained relation of total amount of movement to T1 and
SS was only slightly in accord with the predicted relation, it is suggested
that it is more fruitful and enlightening to consider, separately, the re-
lations of on- skin and off-skin movement to T1 and SS.

b) D need not be inversely related to TI in order to secure maximum
frequencies of either on- skin or off- skin movement; D, in fact, is not re-
lated to occurrence of on- skin movement and probably not to off— skin move-
ment either.

c) Frequency of on- skin movement is inversely related to T1, and
completeness of on- skin movement is inversely related to SS (and to T1
in minor degree). Both quantity and quality of on-skin movement are
heavily dependent on the degree of pliability of the skin tissue. A conceptuali—
zation of the mechanisms involved in on- skin movement is given which
accounts for the on- skin movement results obtained, and which greatly
favors the notion that these mechanisms are peripheral in nature.

d) Frequency of off— skin movement is directly related to T1 and SS
jointly for T1 sufficiently large. At small TIS, off-skin movement is in-
frequent, irrespective of the magnitude of SS. Thus, it is concluded that

”time and room" is needed to make movement through the air possible and

 

that neither "time" nor "room" along is sufficient; hence, it is concluded
that off-skin movement experiences are the result of the incitement of
appropriate visual images.

e) The physical cessation of S is not necessary for the occurrence of
apparent tactual movement phenomena.

f) Experiences of on- _a_n_<_1 off- skin movements are frequently accom-
panied by experiences of pick-up of the stimulating objects from the skin.

It is not entirely obvious why this association was true of on- skin move-

ment as well as of off- skin movement.

73

It is concluded that because on- skin and off- skin movements are
primarily aroused by different S conditions and were believed demonstrated
to depend on different mechanisms, a complete understanding of apparent
tactual movement cannot be achieved unless a distinction between the two
types of movement is maintained.

A number of suggestions for future research in the area were made;
these indicate that additional studies in this area will prove to be extremely

intere sting and enlightening .

REFERENCES

Andrews, W. A. Haptical illusions of movement. Amer. J. Psychol.,
1922, 33, 277-284.

 

Bartley, S. H. Principles of perception. New York: Harper, 1958.

 

Benussi, V. Kinematohaptische Erscheinungen. Arch. ges.Psychol.,
1913, 29, 385-388.

 

Benussi, V. Versuche zur Analyse taktil er’weckter' Scheinbewegungen.
Arch. ges. Psychol., 1917, 36, 59-135.

 

Burtt, H. E. Auditory illusions of movement. J. exp. Psychol., 1917,
2, 63-75.

 

Burtt, H. E. TaCLual illusions of movement. J. exp. Psychol., 1917,
2, 371-385.

 

Dimmick, F. L. An experimental study of visual movement and the phi—
phenomenon. Amer. J. Psychol., 1920, 31, 317-332.

 

Higginson, G. D. The visual apprehension of movement under successive
retinal excitations. Amer. J. Psychol., 1926, 37, 63-115.

 

Hillebrand, F. Fur Theorie der stroboskOpischen Bewegungen. Z. Psychol. ,
1922, 89, 262-272.

 

Hulin, W. S. An experimental study of apparent tactual movement.
J. exp. Psychol., 1927, 10, 293-320.

 

Jones, E. E., and Bruner, J. S. Expectancy in apparent visual move-
ment. Brit. J. Psychol., 1954, 45, 157-165.

 

Judd, C. H. Ueber Raumwahrnemungen im Gebiete des Tastsinnes.
Phil. Stud., 1896, 12, 425-428.

Kelly, E. L. The effect of previous experience and suggestion on the
perception of apparent movement. Psychol. Bull., 1935, 32, 569-570.

 

Korte, A. Kinematoskopische Untersuchungen. Z. Psychol., 1915, 72,
193-296. '

 

Lehrnann, H. Wahrnehmungslehre und Scheinbewegung. Zweiter Teil:
Wesen und Entstehung der Scheinbewegung im Lichte neuer Versuche.
Arch. ges Psychol. , 1939, 102, 375-450.

 

74

75

Mathieson, Anna. Apparent movement in auditory perception. Psychol.
Monog., 1931, 41 (No. 187), 74-131.

Nafe, J. P. and Wagoner, K. S. The nature of sensory adaptation.
J. gen. Psychol., 1941, 25, 295, 321.

 

Nafe, J. P. , and Wagoner, K. S. , The nature of pressure adaptatiOn.
J. gen. Psychol., 1941, 25, 323-351.

 

 

Neuhaus, W. Taktile Scheinbewegungen. Arch.ges. Psychol., 1932,
83, 519-563. -

Pieron, H. Remarques sur la perception du mouvement apparent.
Anne’e psychol. , 1934, 34, 244-248.

 

Ryans, D. G. The phi-phenomenon: a fundamental Gestalt. J. gen.
Psychol., 1937, 17, 155-161.

Schaeffer, A. A. Apparent movement in a diffusely stimulated tactile
field. J. gen. Psychol., 1939, 20, 91-107.

 

Schmid, Ethel. Temporal aspects of cutaneous interaction with two-point
electrical stimulation. J. exp. Psychol., 1961, 61, 400-409.

 

Schnehage, H. J. Versuche fiber taklile Scheinbewegung bei variation
phanomenaler Bedingungen. Arch. ges.. Psychol., 1939, 104,
175-228.

 

Scholz, W. Experimentelle Untersuchungen iiber die ph'anomenale GrOsse
von Raumstrecken. Psychol. Forsch., 1925, 5, 219-272.

 

Stampfer, S. Die stroboskOpischen Scheiben oder Optischen Zauberscheiben,
der Theorie und wissenschaftliche Anwendung. Jahr. polytech.
Instit. (Wien), 1833, 18, 237.

 

Toch, H. H. , and Ittelson, W. H. The role of past experience in apparent
movement: a revaluation. Brit- J. Psychol., 1956, 47, 195-207.

 

von Békésy, G. Human skin perception of traveling waves similar to
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von. Békésy, G. Sensations on the skin similar to directional hearing,
beats and harmonics of the ear. J. Acoust.. Soc. Amer. , 1957,
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von Békésy, G. , Similarities between hearing and skin sensations.
Psychol. Rev., 1959, 66, 1-22.

 

76

von Frey, M. , and Metzner, S. R. Die Raumschwelle der Haut bei
Successivreizung. Z. Psychol., 1902, 29, 179-180.

 

Wertheimer, M. Experimentelle Studien iiber das Sehen von Bewegung.
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APPENDICES

77

APPENDIX A: RESPONSE KEY

Code:

represents a single discrete point

represents a single blunt area (you can allow some variation in the
width of such an area)

represents a continuous line or area (you can allow some variations in
the width and/or length of these lines)

>c:::€% 0

represents movement on the surface of the skin (you can allow some

 

or . . . _—
variation in the lengths of these arrows)

To?" represents movement o_f_f the skin surface, in the air, and the arrow

, ) indicates the direction of movement)

I /
9 indicates sequential order

0

CLASS A: Simultaneous and Single Impression(s)

O

I 0 ® ®
O

i s ® . ®

9.

1. 2. 3. 4. 5. 6. 7. 8.

 

o
@
(...

CLASS B: Successive Impressions
2 2 O O
O ® (’2 82 2 ‘3, / ,6). / /

O
/1 01 01 01
1. 2. 3. a 5. 6. m 8. a 1d 1L

O3

/:)1 @l 01/ $1 0

CLASS C: Movement Impressions

0 g (’8 (I, 0 ® ® C/‘EK 05"

I ۤ - ,
’e‘ g 1 ' I
O o I, ,, 0 ® (5 0’
1. 2. 3. 4. 5. 6. 7. 8. 10. 11. 12.

 

ReSponse categories to use in describing the nature of the departure of the
stimulating object(s) from the skin:

 

 

ReSponse categories Key (use of data sheet)
Fast Pick-up FP
Slow-Pick-up SP

No Pick-up (stayed down or faded out) NP

Not Sure ?

78

APPENDIX B:

DATA SHEET .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cond. Trial Class Type within 8. Nature of Space for drawing
given class departure additional diagrams
1 .

c.
,__£ a.
b.
c.
3 a.
b.
c.
4 a.
b.
c.
5 a.
b.
c.
6 a.
b.
c.
7 4a.
b.
__ C-
8 a.
b.
c.
9 a.
b.
c.
10 a.
b.
c.
11 a.
b.
c.
12 a.
b.
c.

 

I."