9..ka F.“ .2
$3“ 43.

 

A.

   

.n

3.
\4

 

f1
u.

at
.1
x

o £§
:4.

 

 

 

 

 

   
      

  

LIBRARY

Michigan State

was University

This is to certify that the

thesis entitled

RESPONSES TO REPEATED TACTILE STIMULATION IN

THE PLANARIAN: DUGESIA TIGRINA

 

presented by

John M. VAnDeventer

has been accepted towards fulfillment
of the requirements for

MW in P

Mfiw‘

, Major platessor

DateV‘w‘3‘ ’qé7

ABSTRACT

RESPONSES TO REPEATED TACTILE STIMULATION
IN THE PLANARIAN: DUGESIA TIGRINA

 

by John M. VanDeventer

Habituation, which may be Operationally defined as
the repeated application of an unconditioned stimulus,
has, in the past, received little attention. In view
of its importance in connection with a number of other
behavior processes, there exists an urgent necessity to
subject habituation to systematic scrutiny. The present
paper represents an effort to do this. Its aims are
(l) to assess the effects of this process for the

planarian, Dugesia tigrina, (2) to determine whether

 

this species lends itself to further study of the
process and (3) to identify some of the variables
which may indicate the nature of the process.
Definitions of habituation were examined; it was
found that the majority of investigators define habitua-
tion in terms of response characteristics rather than in
terms of procedure. For purposes of the present study,
habituation was described as the repeated application
of an unconditioned stimulus, regardless of the type of
response produced. It was then visualized that changes
other than a response decrement might occur.
A pilot study and four additional studies suggested

by the pilot study are described. In the pilot study,

John M. VanDeventer

the effects of repeated presentation of light, electric
current and tactile stimulation were examined. It was
decided that the use of tactile stimulation might lead
to the most fruitful results. In addition, the results
of the pilot study indicated that changes in response
tOpography may accompany the decline in reSponsiveness,
an observation which earlier definitions of habituation
would have made difficult.

In Study I the effects of repeated posterior
tactile stimulation were studied. A decline in
responsiveness (tail contractions) was observed, but
the change in response tOpography suggested by the pilot
study did not occur. Dishabituation with light indicated
that the effects observed were not due to "fatigue" nor
to receptor adaptation. Dishabituation trials were
significantly correlated with habituation trials
establishing some degree of reliability of the procedure.
It was decided that the change in response tOpography
observed in the pilot study may have been due to
difficulty in applying the stimulus to the same area
on each trial (this was corrected by a stimulus modifi-
cation in Study I and subsequent studies). In Study II
anterior and medial application of the tactile stimulus
was compared to the posterior application of Study I.

It was found that (l) anterior stimulation produced only
tail contractions and turns and that posterior stimulation

produced only tail contractions whereas medial

John M. VanDeventer

stimulation produced both, (2) in the case of medial
application tail contractions declined while head
reSponses appeared to first increase and then decrease
and (3) with anterior application, turns away declined
while turns toward the stimulus increased and then
declined. These results indicate that a change in
response topography takes place with medial and anterior
stimulation.

Study III was designed to observe the retention of
the effects of medial tactile stimulation. These
effects were retained for more than 2a hours but less
than 96 hours. A low correlation between training and
retraining trials suggest that the data was unreliable.
Possible sources of unreliability are discussed. It
was concluded, among other things, that posterior
stimulation would be a better procedure in the study
of the retention of the effects of habituation than
medial stimulation.

Finally, in Study IV, the effects of concurrent
stimulation upon the course of habituation were studied.
Habituation to a posterior tactile stimulus under
conditions of low illumination was compared to habitua-
tion under conditions of a high level of illumination.
The latter required significantly fewer trials to
criterion (three responses in ten consecutive trials)

than was the case during the former condition.

John M. VanDeventer
It was concluded that both a decline in responsive-
ness as well as a change in response tOpography under
some conditions as a result of repeated tactile
stimulation occurs in the planarian, Q. tigrina; and
that the Species may be profitably studied in this
respect providing that additional studies be undertaken

to identify possible sources of "noise" in the procedure.

RESPONSES TO REPEATED TACTILE STIMULATION
IN THE PLANARIAN: DUGESIA TIGRINA

 

by

'l‘:

,
l L

1 y‘
, {)l .
John M. VanDeventer

A THESIS

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

DOCTOR OF PHILOSOPHY

DEPARTMENT OF PSYCHOLOGY

1967

GHQW’AK.
iS-lt—é}?

ACKNOWLEDGEMENTS

I wish to express my appreciation to my wife, Luise,
and two children, John and Carla, for tolerating the
various inconveniences arising out of the following
study, perhaps eSpecially for being able to live with
worms in the living room and vats of boiled water in
the kitchen. I wish also to express my gratitude to
my good friend and advisor, Professor Stanley Ratner
who has rendered invaluable advice, suggestions and
other help during the preparation of this study as well
as upon other occaSions. I would also like to extend
this gratitude to the other members of my committee,
Professors John King, Paul Bakan, and Bill Stellwagen
for their suggestions and sudden Sunday morning
c00peration; and finally to my secretary, Mrs. Marilyn

Howard who typed the final manuscript.

iii

TABLE OF CONTENTS

Page
Acknowledgements— -------------------------------------- ii
List of tables- ________________________________________ iv
List of figures— --------------------------------------- v
List of Appendix I figures- ---------------------------- vi
List of Appendix II tables- ---------------------------- vii
Introduction __________________________________________ 1
Definition of the area of investigation ___________ 2
Habituation research with planaria ................ lO
Planaria as an object of study .................... 12
Results of the Pilot Studies ........................... 14
Study One: Light ................................. 15
Study Two: Electric Current ...................... 15
Study Three: Tactile Stimulation ................. 16
Discussion of pilot study results ................. l7
EXperiment I: The Effects of Repeated Tactile
Stimulation: Posterior application _______________ 19
Gethod -------------------------------------------- 19
Results ------------------------------------------- 21
Discussion ---------------------------------------- 25

Experiment II: The Effects of Repeated Stimulation:

Anterior and Medial application .................. .27
Method ............................................ 28
Results .......................................... 29
Discussion ........................................ 36
Experiment III: The Effects of Repeated
Stimulation: Retention Tests ..................... 38
Method -------------------------------------------- 39
Results .......................................... 40
Discussion ........................................ 50
Experiment IV: The Effects of Recurrent
Stimulation: .................................... .55
Method ........................................... .56
Results .......................................... -56
Discussion ........................................ 56
Summary and Conclusions ------------------------------- -6l
References ------------------------------------------- '63
Appendix I -------------------------------------------- ‘66
Appendix II ............................................ 71

iii

LIST OF TABLES
Table

1 Means, standard deviations and differences
between means for posterior contractions
to the stimulus in Experiment I for each
block of trials -----------------------------

2 leans and standard deviations of frequency
of anterior responses to the stimulus in
Experiment I for each block of trials -------

3 Means and standard deviations of frequency
of anterior responses of the random group
in Experiment I for each block of trials----

4 Means, standard deviations, and differences
between means for various loci of stimu-
lation in Experiment II ---------------------

5 Means, standard deviations, and differences
between means for turns away from the
stimulus in Experiment II for each block
of trials -----------------------------------

6 Means, standard deviations, and differences
between means for turns toward the stimulus
in Experiment II for each block of trials---

7 Means, standard deviations, and differences
between means for retention intervals in
Experiment III ------------------------------

8 Correlation coefficients between habituation

trials and rehabituation trials to criterion
in Experiment III ...........................

9 Means, standard deviations, and differences
between means for trial blocks of Posterior
Contractions in Experiment III --------------

10 Means and standard deviations for trial
blocks of all anterior responses in
Experiment III ------------------------------

ll Means and standard deviations for trial
blocks of anterior turns in Experiment III--

12 Means and standard deviations for trial
blocks of anterior contractions in
Experiment III ------------------------------

13 Means, standard deviations and differences
between means for tactile stimulation

with and without concurrent light stimulation
iv

Page

23

2h

24

31

34

35

42

#3

A7

48

48

#9

Figure

1

LIST OF FIGURES
Page

Pesponse frequency as a function of

blocks of trials for the posterior

stimulation and random response groups

of Experiment I ----------------------------- 22

Frequency of anterior turns as a function
of locus of stimulation with responses
of the random group ------------------------- 30

Turns toward and turns away from an
anterior applied stimulus as a function
of blocks of trials in Experiment II -------- 33

Savings score as a function of retention
interval ------------------------------------ 41

Posterior and anterior responses as a
function of trial blocks in Experiment III-- 45

Anterior turns and anterior contractions
as functions of trial blocks in
Experiment III ------------------------------ 46

Comparison of posterior contractions

as functions of trial blocks for

habituation and rehabituation in Experiment

III ----------------------------------------- 52

Comparison of anterior responses as
functions of trial blocks for habituation
and rehabituation in Experiment III --------- 53

Posterior contractions for subjects
with and without concurrent light
stimulation in Experiment IV ---------------- 57

LIST OF APPENDIX FIGURES

Figure Page

Izl Contractions and turns in response to
light as a function of trial block,
Pilot Study One -------------------------- - 67

1:2 Results of Pilot Study 1, dark adapted
group ------------------------------------- 68

1:3 Results of Pilot Study 2, Contractions
and turns in response to shock as a
function of trial block ------------------- 69

1:4 Results of Pilot Study 3, Contractions

and turns in response to tactile
stimulation ------------------------------- 70

vi

Table

LIST OF APPENDIX TABLES

Ilzl Summary of the Analysis of Variance of

II:

II:

II:

II:

II:

II:

II:

II:

trial block scores for posterior
contractions in Experiment I ................

Summary of the Analysis of Variance of
locus by stimulation scores in
Experiment II -------------------------------

Summary of the Analysis of Variance of
trial block scores for turns away from
the stimulus in Experiment II ---------------

Summary of the Analysis of Variance of
trial block scores for turns toward the
stimulus in Experiment II -------------------

Summary of the Analysis of Variance of
the retention interval in Experiment III----

Summary of the Analysis of Variance of
trial block scores for posterior
contractions in Experiment III --------------

Summary of the Analysis of Variance of
trial block scores for all anterior
reSponses in Experiment III -----------------

Summary of the Analysis of Variance of
trial block scores for anterior turns
in Experiment III ---------------------------

Summary of the Analysis of Variance of

trial block scores for anterior
contractions in Experiment III ..............

vii

Page

72

72

72

73

73

73

74

74

74

INTRODUCTION

The field of study generally subsumed under the
term "Habituation" has rarely occasioned any systematic
study. This seems singularly strange insofar as some
type of "acclimitization" procedure - which, among
other phenomena, includes habituation - precedes the
laboratory investigation of other processes in nearly
all vertebrate phyla. This kind of procedure seems to
be less evident in invertebrate studies but this lack
may reflect more the relative paucity of investigations
of these organisms rather than the inapprOpriateness of
such a procedure.

Those studies of infrahuman organisms which have
been conducted in the past have been largely defined by
interests and problems stimulated by practical human
Psychology rather than a general Psychology which ignores
phylogenetic boundaries. It is probably for this reason
that habituation has been passed over lightly. While it
may constitute a major mode of response modification in
the invertebrates, its role in human behavior has been
obscured for multiple reasons. First, human behavioral
complexity and a variety of people creates a situation
where habituation is less readily observable and some-
what less interesting. Second, the majority of
psychological investigations have been undertaken with
adult subjects, that is to say, with subjects that may
be to a considerable extent already habituated to a

l

.2
variety of stimuli. Third, the theorists of the
thirties deemphasized instinct theory and therefore the
analysis of the unconditioned response was deemphasized.

In the last few decades, however, the importance
of habituation as a factor in human behavior has become
clearer. Its relationship to learning has been emphasized
(Maltzman and Raskin, 1965). A greater concern with
problem areas other than learning where habituation is
more readily seen has also lead to a greater interest
in response decrement as, for example, the study of
vigilance (Bakan, Belton and Toth, 1963) or as an
explanation of the inability of the feebleminded to
learn (Denny, 1964).

Zoologists have possessed a greater interest in
the phenomenon of habituation than Psychologists have
and, as a result of this greater interest, nearly all
of the earlier research studies of the process have been
under their leadership. Nevertheless, their inquisitive-
ness has been directed more to the demonstration of its
existence in some one species rather than to the
systematic inquiry after its prOperties and nature.

The present study was conceived in the Spirit of
establishing a rude beginning of a systematic investi-
gation.

Definition g§_thg Aggg 9; Investigation. The
relative sparsity of systematic research dealing with

habituation demands that the definition of the phenomenon

3

be subjected to careful scrutiny. A recent concern
with operational definitions in the experimental lit-
erature begs clarification of one point at the onset
of this discussion, yig.,whereas most writers appear
to set up rigid specifications of a phenomenon (pre-
sumably following the lead of the natural scientists),
such definitions are not in fact altogether warranted
in the absence of precise theoretical formulations
relating the variables in the domain of experience
concerned (Frank, 1957). Furthermore, even granted
a formal theory, the general notion of an event need
not be as rigidly Specified as would be necessary in
the case of a concrete problem deriving from the
theory (Nagel, 1957). Thus, the most desirable course
to follow would be to admit of as broad and neutral a
definition as is possible and reserve the more precise
formulations for the level of a particular experiment.
In cases where we know little about a phenomenon even
the latter suggestion should be relaxed to some degree.

It will be argued that the majority of previous
workers have become more and more Specific in their
definitions of habituation and as a result of this
rigidity may have directed attention away from in-
vestigational strategies which might lead to the
determination of the nature of the phenomenon. Harris
(1943) probably represents the earliest attempt to

review the scattered studies of habituation. He defines

L,
the process as follows (evidently establishing the
precedent for future workers):

(By habituation) . . . what is referred to
are all those instances of decrement in
magnitude of unlearned responses (I) which
occur centrally in the intact organism, (2)
which are due to repetitive stimulation
activation, and which may . . . be dis-
tinguished from the types of response
decrement occurring as a result of, for
example, receptor adaptation, loss of the
effector's ability to respond, or any of
the various types of inhibition. (p. 385)

Later, Thorpe (1961), apparently in an effort to
revive interest in habituation, offers a similar def-
inition:

Used in its widest sense, habituation is a

Simple learning not to respond to stimuli

which tend to be without significance in

the life of the animal; and stimuli without

significance obviously cannot release con-

sumatory acts. Habituation thus implies a

tendency merely to drOp out responses, not

to incorporate new ones or complicate those

already present. In this respect it is

pertainly the simplest kind of learning. ...
p. 21

Thorpe's otherwise excellent review (1961), in

search of precise formulation of habituation, commits
a major error: explanation of a poorly understood
process in terms of another poorly understood (albeit,
not quite as) process, yig,, learning. Were there any
relationship between the two, habituation is most
analogous to extinction and the explanation of extinc-
tion as learning not to respond is certainly not above
question (Kimble, 1961). It would be more prudent to

maintain an independence from learning in the study of

5

habituation until the evidence shows, more vividly, the
relationship (this evidence, indeed, would probably be
in the form of the identification of the physiological
substrates of the two processes).

A more recent paper was even more specific: Thompson
and Spencer (1966) suggest that habituation acts in the
following manner:

Given that a particular stimulus elicits a

response, repeated applications of the stimulus

result in decreased responses (habituation).

The decrease is usually a negative exponential

function of the number of stimulus presentations.

(p. 18)

In addition, they maintain that the phenomenon has the
following prOperties: (1) spontaneous recovery, (2)
more rapid habituation after a series of habituation
trials and Spontaneous recoveries, (3) the more rapid
the frequency the more rapid the habituation, (4) the
weaker the stimulus, the more rapid the habituation,
(5) strong stimuli may yield no habituation, (6)
stimulus generalization occurs, (7) dishabituation
occurs with another strong stimulus, (8) and finally,
the dishabituating stimuli tend to habituate as well.
Thompson and Spencer (1966) further assert that the
extent to which any observed response decrement fits
these prOperties will determine whether there has beenj
habituation. It seems grossly premature to specify the
prOperties of a process which has not yet been adequately

surveyed. For example, the almost total lack of any

systematic study of invertebrate species leaves us

6

without a frame of reference against which to view the
more extensive vertebrate studies. This neglect of
invertebrates leaves Psychology in a position which
would be analogous to the investigation of hormone
chemistry in ignorance of inorganic chemistry. When
psychology looks to the natural sciences it usually
cannot see the strategy because of the instruments.
Habituation in vertebrate species may (1) be an
entirely different process than the analogous type

of behavior in invertebrates, (2) or, as we go "up"
the phylogenetic scale, a particular simple process
may more reflect the influence of other behavioral
processes than it does its own individual properties,
(3) or finally, what is called habituation in ver-
tebrates may be a complex of processes which do not
occur in that combination in "lower" species. Only
additional research, unfettered by such heavy defi-
nitional chains can delineate the nature of the process.
Of paramount importance is a thorough study of inver-
tebrates.

All of the above cited reviewers (as well as
persons conducting specific investigations) tend to
identify the site of effect when the effects of repeat-
ed stimulation are being considered. Generally speaking,
most investigators make some attempt to distinguish
whether the effects observed are taking place centrally

or peripherally and, if the latter, whether in the

7
receptor or the effector side of the "reflex arc."
The procedure usually applied is termed "dishabituation."
This procedure may take several courses; the site of
stimulation may be changed and if, as a result, the re-
sponse rate increases, then "fatigue"nay be ruled out--
but not receptor adaptation; but receptor adaptation and
fatigue may be ruled out by applying a second stimulus
concurrent with the habituation stimulus after it has
been established that the second stimulus does not
elicit the reSponse in question; receptor adaptation--
but not fatigue--may be ruled out if a different
response can still be elicited with the same stimulus.
Still another procedure may be used: if the retention
of the effect is relatively long, then both receptor
adaptation and fatigue, the effects of Which are of
brief duration, may be ruled out. If the effect is not
transient, it may be argued that is central in locus.
This is, at best, questionable since unwarranted assump-
tions are being made about central events. Failure to
dishabituate or failure of retention may not necessarily
vitiate the interpretation of habituation.

In a discipline noted for its disagreements, the
definers of habituation stand out with their essential
agreement. With the manner in which they have agreed to
define habituation (as a form of learning and with the

exact specification of the response) they have led us

8

away from the major research problem associated with
habituation. By Specifying the response side of the
process, any theoretical formulations would undoubtedly
explain why habituation occurs but not why it does not
occur. The same problem seems to have arisen in the
area of learning; interest in the behavior change has
caused failures to change to become largely ignored.
Thus current learning theories, while they enable us to
explain why learning will occur, do not enable us to
easily predict when it will-not occur (that is due to
impossibility rather than poor procedure) even though
the usual learning paradigm is applied. It is evident
that this state of affairs has been brought about by a
study of the learning process as defined by responses
rather than a study of the learning paradigm. Only a
theory which explains why something did not occur is
adequate.

The purpose of the present discussion is to draw
attention to the possibility that a reSponse decrement
is one of several possible response outcomes which may
result when the habituation paradigm is applied. This
suggestion has recently been tendered in a review of
Annelid learning by Ratner (1967). If the term
"habituatinn" refers to a type of response outcome,
yig., a decrement, then the past reviewers have shirked
their reSponsibility in failing to study the broader

problem, i.§., the effects of repeated unconditioned

stimulus presentation.

Viewing the problem in this fashion now makes
possible some preliminary comments about habituation.
First, at least methodologically, habituation is not the
same thing as learning when the latter is viewed as
repeated presentation of two stimuli rather than just
one. Second, it is methodologically different from ex-
tinction in that while both result from the repeated
presentation of a single stimulus, the complete defini-
tion of extinction requires the inclusion of the
previous learning paradigm. Indeed, we might suspect
that insofar as learning is defined by research with
"higher" vertebrates, the term may well include a
variety of processes (one of which may be habituation).
To state now that habituation is a simple form of learn-
ing seems at best confusing and nothing is lost by
eliminating any mention of learning from a definition of
habituation.

The present study, then, is conceived as a study of
the effects of repeated presentation of an unconditioned
stimulus, whatever the outcome of such a paradigm.
Within this framework, it is now possible to ask what
different outcomes may be expected when an organism is
repeatedly exposed to a stimulus. Such a course could
produce no change, a response increment, a response
decrement, a change in response t0pography, or some

combination of these outcomes. On the basis of actual

10

research have any of these outcomes been observed?
Rushforth (1965) reports that while a response decrement
was found to occur with repeated mechanical stimulation
in Hydra pirardi, no change was observed with respect to
light in spite of 200 presentations of the latter.
Response increments commonly occur and are generally
subsumed under the term "sensitization." Here complex
changes have been observed to occur; for example,
Gardner (1966) describes the habituation of Lumbricus
terrestris to vibration as involving two types of
reSponses, one of which dr0ps out before the other.
Wendt (1951) has reported that during the habituation
of nystagmus not only does the movement decline but
may go in the direction Opposite of the original
(secondary nystagmus). It is a general known fact
that for vertebrates, the reSponse to a strange stimulus
may first involve an immobility response, then a with-
drawal reSponse which decrements to a state of "alert-
ness" which is replaced by incrementing approach
reSponses which may in turn tend to decrement.

Habituation Research with Planaria. In the course
of the study of habituation, planarian species seem to
have been virtually ignored. Harris in his review (1943),
cites only one study, Pearl (1903). The latter inves-
tigator found a response decrement to mechanical
stimulation applied to the anterior end. Conditions

under which the study was made are not described. Harris,

11
however, seems to have missed two other studies:
Walter (1908) reported a response decrement to rotation
of the subjects' bowl as well as a decline in reSpon-
siveness to the crossing of a light-dark boundary;
Dilk (1937) reports a response decrement for Dugesis
gonocephala when vibration was presented for one
minute or longer with inter-trial intervals of not more
than 10-15 seconds. These three poorly described
studies appear to be the only ones, barring brief
asides in the studies of other processes, i,§.,
Thompson and McConnell (1955) in their study of classical
conditioning in the planarian D, dorotocephala note that
their light control group showed a slight decline in
responsiveness to light, until a report by Best and
Rubenstein (1962) that planaria delay feeding in an
environment with which they are not familiar. This
study, however, suffers from the failure to include a
handling control group and to include data on the size
of the food which in large concentrations may act as
an aversive stimulus. This is particularly important
in view of the fact that the Species used (Qgrg
foremanii) by Best and Rubenstein (1962) is very
sensitive to contamination (VanDeventer, 1963). Best's
and Rubenstein's paper was followed by a report by
Westerman (1963). In this study a response decrement to
light was retained over several days. This study is

difficult to place in prOper perspective with other

12
of habituation insofar as "practice" was given through-
out the retention interval, i,§,, the method of dis-
tributive practice, commonly associated with learning,
was used.

In summary, habituation in planarian species is
certainly indicated but has not been clearly established.
Variables which affect the habituation of responses have
not been reported. The restrictive definition of
habituation as a response decrement has guided these
previous studies.

Planaria §§.gg_0bject 2£.§pgdy. Planaria have
been selected for study in the present investigation
for a variety of reasons. First, my previous research
has dealt largely with this particular group (VanDeventer,
1960; VanDeventer, 1963); VanDeventer and Ratner, 196A;
Ratner and VanDeventer, 1965). Second, it is my bias
that there exists an urgent necessity to study and
understand the behavior of the "lower" invertebrates.
Third, planaria have become increasingly pOpular as
objects of investigation in Psychology. This pOpularity
has centered primarily around learning and thus there is
a necessity for studies of less glamorous tOpics in
order to place the learning research in prOper perspective.
Other, more mundane reasons such as the ready availability
of subjects and materials for their care, have, of course,
in the past, played some role in the choice of this

animal for research.

13

To recapitulate, the aim of the present study is
severalfold: (l) to conduct a study of habituation
free from the strictures of the earlier investigations,
(2) to determine the effects of repeated stimulation
on planaria, (3) to determine whether or not such
effects may be easily studied in this particular group
of animals, (4) and finally to consider a few variables
which might affect the nature and direction of the
effects. This investigation, then, is essentially

exploratory and descriptive in nature.

RESULTS OF THE PILOT STUDIES

In consideration of the lack of research dealing
with the effects of reported stimulation on planaria
several pilot studies were conducted in order to deter-
mine the most appropriate beginning to the undertaking
of the present study. Three primary objectives might
be realized by such preliminary studies: (1) which
particular stimulus would be the most appropriate to
study; (2) identification of possible response changes
other than a decrement in responding; (3) and deter-
mination of difficulties which might arise with regard
to questions of technique, measurement, 23g.

Planaria are sensitive to a wide variety of energy
form such as light (Parker and Burnett, I901), temper-
ature (Mast, 1903), gravitational forces (Olmsted, 1917),
chemical gradients (Wulzen, I916), electric current
(Shafer and Corman, 1963), tactile stimulation (Walter,
1907) and water current (Beauchamp, 1937). Temperature
changes, chemical change and changes in water current
were ruled out at the onset due to obvious difficulties
inherent in controlling these forms of stimulation in
studies of brief, intermittant stimulus presentation.
Whereas gravitational changes might be produced
readily and rapidly, such changes would be easily
confounded with changes in water current and alterations

of chemical gradients; thus this form of stimulation was

14

15
also ruled out. It was decided to consider the relative
advantages of light, electric current, and tactile stim-
ulation.

Study One: Lighp. Brief pulses of light (one
second) with a Short inter-trial interval (three seconds)
were presented to two groups of Dugesia tigrina. One
group was light adapted, the other, dark adapted. A
third group was observed for the random response fre-
quency. As Halas, James, and Stone (1961) have previously
noted, there were two types of responses to light:
anterior turns and contractions. The former predominated
whereas the latter rarely occurred. Inspection of
Appendix Figure 1:1 for the light adapted group reveals
a distinct reSponse decrement with regard to turns as a
function of trials. The same trend appears to occur
with the contractions but the incidence seems to be too
low to be subjected to analysis. Inspection of Appendix
Figure 1:2 for the dark-adapted group reveals that
dark adapted subjects do not habituate appreciably to
light over the same interval used with group 1. These
subjects also Show no contraction reSponses in contrast
to the light adapted group.

Study Two: Electric Current. One group of Q.
trigina was treated in the same way as in Study One
except that electric current was used rather than light.
As in the case of a previous study (Shafer and Corman,

1963) two types of responses to electric current were

16

observed: anterior turns and longitudinal contractions
(usually anterior). Whereas Shafer and Corman interpret
their study in such a way as to suggest that the type of
response is a function of head orientation with regard
to the polarity of the electrodes, such an explanation
seems untenable here insofar as 60 cycle alternating
current was used rather than direct current as was the
case in the Shafer and Corman investigation (1963).
Appendix Figure 1:3 shows slight habituation of the
contractions and no apparent habituation of the turns.
It is of some interest to note that the turn frequency
shows a possible increment after repeated stimulation.

Study Three: Tactile Stimulation. One group of

 

D. tigrina was touched briefly on the posterior and
with a human hair; the inter-trial interval was five
seconds. With this group a criterion of habituation
was used (only three responses out of ten consecutive
trials) and when the criterion had been reached, dis-
habituation trials were given. These consisted of
turning on an overhead light and immediately following
this with tactile stimulation. The responses to tactile
stimulation were (in order of decreasing frequency)
posterior contractions, single anterior turns, anterior
contractions, head waving, momentary cessation of
locomotion. The latter two responses occurred very
rarely. Each type of reSponse occasionally would occur

in combination with any of the others. Appendix Figure

17
l:4 depicts posterior responses (contractions) and
anterior responses (Largely turns and contractions but
head waving and stOpping are also included) as a function
of trials as well as the results of the dishabituation
trials. Whereas a decrement in the posterior responses
is definitely indicated, the anterior responses suggest
an interesting course, 115., an increment in response
which is followed by a decrement. The dishabituation
trials rule out both "fatigue" and sensory adaptation
(as only posterior contractions are shown and Study One
found no such reSponses to light, therefore, those
contractions must be to the tactile stimulation). The
subjects of this study were dark-adapted and were tested
in the dark. An additional two subjects were tactilly
stimulated in the presence of continuous light from a
100 watt bulb suspended 8 inches above the test chamber.
These subjects appeared to habituate to the tactile
stimulus in remarkably few trials.

Discussion gf the Pilot Study Results. In general,
the results of the pilot study were encouraging. The
results seemed to be the most primising in the case of
tactile stimulation. This seemed definitely to be an
exception to the usual definition of habituation.
Dishabituation to tactile stimulation produced a
majority of posterior contractions when light was used
as a dishabituating stimulus. Neither light nor shock

produced any tail contractions whereas tactile stimu-

l8
lation elicited a majority of posterior contractions as
well as a number of anterior turns. While fatigue could
be ruled out with any of the above stimuli with a
dishabituation procedure, sensory adaptation could not
be so easily excluded if either light or shock were
used, insofar as anterior turns could be attributed to
the dishabituation stimulus whether it were light,
electric current or a tactile stimulus. On the other
hand, if tactile stimulation were used to habituate,
then either light or shock could be used in the dis—
habituation procedure since neither of these appeared
to elicit tail contractions. It was thus decided to
continue the study with tactile stimulation even
though this form of stimulation is more difficult to
control than either electric current or light.

The pilot studies suggested the following inves-
tigations: A more carefully controlled study of the
course of responses to repeated tactile stimulation in
2, ti rina, the effects of background stimulation upon
the phenomenon in question and the retention of the
effects of repeated stimulation. The use of the hair
created undue problems of control so that the tactile

stimulus was altered for the ensuing investigations.

EXPERIMENT ONE: THE EFFECTS OF REPEATED TACTILE
STIMULATION; POSTERIOR APPLICATION
METHOD

Subjects. 2O 2. tigrina were arbitrarily selected
and divided into two groups. The colony of planaria
had been collected from the Fox River beneath the spill-
way of the dam across the river at Burlington, Wisconsin.
They were maintained in boiled tap water--approximately
50 per quart~~which was changed after each feeding of
raw beef liver. They were fed once a week and were
kept in total darkness. Subjects were tested 3-5 days
after feeding and members of one group were tested
alternately with members of the other group. The 88
were 7-10 mm. long. No testing was attempted until the
colony had been in the laboratory for at least a month.
The laboratory temperature was 70° F.

Apparatus and procedure. One S at a time was

 

transferred by means of a medicine drOpper pipette'
(with an enlarged hole) from its home container to the
test chamber which was a round milk glass cereal bowl
and was allowed to swim for one minute prior to testing.
Testing was accomplished in a dark room with a 7% watt
red darkroom buib suspended 10 inches above the test
chamber. The test stimulus was modified from the one
used in the pilot study. An enameled copper wire was
affixed to a match stick with paraffin wax. The tip of
the wire was then heated in a flame until a ball was

formed at the end of the wire. Measurements of the ball

19

20
and wire diameters were taken with the aid of a micros-
cope micrometer eyepiece. The diameter of the ball was
approximately 0.4 mm. and the wire diameter was 0.1 mm.
The ball on the tip permitted contact without fear of
puncture and enabled E to more easily apply the test
stimulus to the same area and, in addition, produced
approximately the same amount of contact from trial to
trial. For the experimental group (I) a trial consisted
of momentarily touching the posterior tip of S with the
test stimulus. The ITI was 4 seconds. Responses which
were expected to occur were posterior contractions,
anterior turns, anterior contractions, head waving and
momentary cessation of locomotion. All responses which
occurred one second after the onset of stimulation were
recorded. Testing of an S was discontinued when S
failed to reSpond 7 out of 10 consecutive trials. When
S had met this criterion, dishabituation was given.
This consisted of turning on a 100 watt bulb for one
second. The bulb was suspended 8 inches above the test
chamber. Immediately following the onset of the light,
S was touched on the posterior. The same ITI and same
procedure for recording reSponses during habituation
was used during dishabituation trials. Ten dishabituation
trials were administered. For the control group (II), a
random reSponse group, the same procedure was followed
except that the test stimulus was not applied and S's

behavior was observed every 4 seconds for a period of

21
one second during which time all responses were recorded.
All 83 in group II received 70 trials and no dishabitua-
tion test was administered.
RESULTS

The results of this study, depicted in Figure 1,
indicate that a reSponse decrement occurred as a result
of repeated stimulation with respect to posterior con-
tractions. Comparison of the anterior responses of
group I with those of group II (the random response
group) indicate that anterior reSponses to tactile
stimulation do not appear to differ significantly for
the two groups in contrast to the results which had
been obtained in the pilot study.

In the case of posterior contractions, on the other
hand, a large number of responses were elicited. Group
II (random response group) exhibited no posterior con-
tractions. An analysis of variance (Appendix Table II:l)
revealed a significant effect (F=5.85, p<:.Ol) of trials
on posterior contractions. Means, standard deviations
and differences between means are provided in Table l.
The latter were analyzed with Duncan's range test,the
results of which are also indicated in Table l. Toward
the end of the curve in Figure l, the function flattens
out slightly and then drops; this is probably an
artifact of the loss of over half the subjects after
trial block V. The mean dishabituation score does not

differ significantly from the first two trial blocks

22

.OH ma : .UomeHUcw no: Co£3 .20fihopwpo weapoos no: access can ..m;w
.oadsmm one :a mnflcflmsoh mm Mo hopes: one opmowecfl mmmonpcopmm SH monsmflm
.H pcosflemmxm mo mddopw ownedmoe Eocene new cowpmHSEwpm howhomeQ one

pom manage Cop mo wxooan mo coapoCSM m>mm honosvonm omSOQmmmun.H meswwm

xooam amass
.neemae HHH> Has H> > >H HHH HH H
(q qlllllll¢11 a a «llllllld - a

\\\\\HUUUI¢ u - \\oll I H
. -.----.!-.J.V«/._ I.-.
Amucv , ./l..LvA.Hu

 

 

 

ans / .. e
Amnpzp poahopcmv

Quopw oncommop Sousa.» Illa... 1 N:
manna .Horuopcm ollllll.

mcoflpomhpcoo nowhopmoa I 8

 

esuodseg

Aouenbeag

23

Table 1. Means, standard deviations, and differences
between means for posterior contractions to the stimulus
in Experiment 1. for each block of trials.

 

 

 

 

Trial Block I II III IV V VI Dishab.
Mean 8.0 6.8 5.9 5.9 4.0 5.0 8.3

S. D. 1.73 1.89 2.11 1.23 1.58 1.73 1.90

N 10 10 IO 9 9 4 IO

 

Trial Block

 

I 8.0

II 6.8 1.8

III 5.9 2.1* .9

IV 5.9 2.l* .9 0.0

V 4.0 4.O=v'< 2.8* 1.9 1.9

VI 5.0 3.0* 1.8 .9 .9 1.0
Dishab. 8.3 0.3 1.5 2.4* 2.4* 4.3):< 3.3

 

 

3::p < .05

24

Table 2. Means and standard deviations of frequency of
anterior responses to the stimulus in Experiment I for
each block of trials.

 

 

 

 

Trial Block I II III IV V VI
Mean 1.6 1.7 1.6 1.2 1.0 1.0
S. D. 1.11 .84 1.28 1.29 1.05 .71
N 10 10 10 9 9 4

 

 

Table 3. Means and standard deviations of frequency of
anterior responses made by the random group in Experiment
1 for each block of trials.

 

 

 

Trial Block I II III IV V VI VII
Mean 1.7 1.4 0.8 1.0 0.9 1.3 0.9
S. D. 1.00 1.20 .60 1.00 0.83 1.11 1.22

 

N 10 10 10 10 10 10 10

 

 

25
but does differ significantly from the remaining trial
blocks. While blocks after block VI are shown in the
figure, they are not included in the analysis due to the
small N involved. The mean trials to criterion for the
group was 44.9 trials.
DISCUSSION

The results of Experiment One clearly indicate that
repeated posterior stimulation results in a decrement of
posterior contractions with no apparent changes in
response t0pography. This is contrary to the expectations
generated by the pilot study in which it appeared that
there were a Significant number of anterior turns the
habituation of which took a different form than the
habituation of the posterior contractions. The dis-
habituation procedure clearly restored the frequency of
posterior contractions to its original level and thus
ruling out fatigue. That these posterior contractions
were not responses to the dishabituation stimulus (light)
is indicated by the results of the pilot study where no
such reSponses were elicited by light; adaptation of
tactile receptors is thus ruled out as an explanation
of the decrement observed. The failure to replicate the
results of the pilot study will be discussed in the
next experiment which was conceived in part as a result

of this failure.

26

The validity of the interpretation that dishabitua-
tion restored the responsiveness to normal was checked
by doing a product moment correlation between the first
block of habituation trials and the 10 dishabituation
trials. The correlation obtained was r=.75; a t-test
performed on this correlation indicated that it was
significantly different from zero (t=3.21; d.f.=8;

p <. .01).

EXPERIMENT TWO: THE EFFECTS OF REPEATED STIMULATION
ANTERIOR AND MEDIAL APPLICATION

At the time that the pilot study was completed,
one explanation for the change in reSponse topography
due to repeated stimulation which was considered, was
that the posterior contractions represented withdrawal
reSponses whereas the anterior responses might be
interpreted as approach responses. Some of the anterior
turns which the subjects made were nearly 180°; it
seemed as if, on these occasions that the subjects
were attempting to reach the test stimulus. Such an
interpretation is further supported by Pearl's observa-
tion (1903) that planaria tend to stOp in the corners
of their containers, as well as by the results of
VanDeventer and Ratner (1964) which suggest that
responsiveness to light may be reduced by increased
body contact with a surface. Insofar as Pearl (1902)
has made the generalization that planaria tend to react
to weak stimuli with a positive reaction and to strong
stimuli with a negative reaction, we might have pre-
dicted the pilot study results, 1.2., a decrement of
posterior contractions accompanied by an increment of
anterior turns; with repeated application, a strong
stimulus becomes functionally a weak one. The present
study was thus projected to examine this hypothesis and

add support to the interpretation of anterior turns

27

28

during tactile stimulation as approach reSponses. In
view of the outcome of Experiment 1, this latter inter-
pretation appeared less tenable. However, a few casual
observations suggested that the study might still be
worth the effort, as it might be possible to explain

the differences between the results of the pilot study
and Experiment 1. In the pilot study the test stimulus
consisted of a hair which was applied to the side of

the subject p333 the posterior, whereas the test stimulus
of Experiment I was applied to the posterior tip of the
subject. A few tests revealed that if the test stimulus
were applied to the anterior of the subject, all the
responses seemed to be turns. One might therefore
predict that if the test stimulus were applied to the
medial area of the subject, both posterior and anterior
responses would result and thus the differences between
the results of Experiment 1 and the pilot study could be
explained.

Experiment 2 was thus designated to examine two
considerations: (1) the hypothesis that anterior
reSponses would increase as the stimulation locus is
moved toward the anterior, and (2) to examine the course
of habituation to a tactile stimulus applied to the
anterior; more Specifically, to see if turns away would
decline and turns toward the test stimulus would increase.

Method

Subjects. 20 naive Q. tigrina as described in

29
Experiment 1 were divided into two groups: a medial
stimulation group and an anterior stimulation group.
Data from Experiment I was used for the posterior
stimulation group. Experiment 2 was conducted at the
same time as Experiment 1, being broken up in this
fashion for eXpository purposes.

Apparatus and Procedure. The procedure was the

 

same as that utilized for Experiment 1, except SS in
Group III were touched with the test stimulus on the
anterior just posterior to the auricles and Group IV
was touched on the side at the midline (referred to as
medial stimulation). All reSponses described in
Experiment 1 were recorded. For Group III, the direction
of an anterior turn with respect to the stimulus was
recorded as "toward" or "away" (only anterior turns
were elicited by the test stimulus when applied to the
anterior. All SS received 50 trials.
Results

The frequency of anterior turns for 50 trials for
various loci of stimulation are depicted in Figure 2.
Also presented are the frequencies of all responses (all
posterior plus all anterior) for each group as well as
the frequency of such reSponses for the random response
group from Experiment 1. An analysis of variance
performed on the groups indicates that the site of
stimulation significantly (p‘4 .Ol) affects the frequency

of anterior turns (summary of the analysis of variance

Frequency

Response

30

 

 

 

35 F
.-———__-.-_—-”’
30 _
-——-—§ anterior turns
-----o all reSponses
—--—o random group
(anterior turns)
25 ..
20 _.
15 ..
lO ..
5 ..
l n l
Posterior Medial Anterior

Stimulation Locus

Figure 2.--Frequency of anterior turns as a function of
locus of stimulation with responses of the random group
(Experiment 1) shown as means of all types of reSponses
for the three loci of stimulation groups. The data for
the posterior stimulation group is from Experiment 1.

31

Table 4. Means, standard deviations, and differences
between means for various loci of stimulation in
Experiment II. All Ss received 50 trials, posterior
and random data from Experiment 1. A Fartley F-max
test indicates that the variances (F=31) are Signifi-
cantly different. A Kruskal-Wallis test (H=35.2)
indicates that the effect of loci of stimulation on
responses is significant. The analysis of variance
data is retained to be consistent with the rest of
the paper.

 

 

 

random post. med ant.
Group response stim. stim. stim.
m??— 5.6 5.9 11.4 33.0
S. D. 1.91 1.76 2.94 9.74
N 10 10 10 10

 

Group
N 5.6

My 5.9 0.3

REE—EL— 11.4 5.8* 5.5..
m 33.0 27.z.=:= 27.12. 21.6..

 

 

*Significant, p < .05

32
may be found in Appendix Table 11:2). ieans, standard
deviations, and differences between means are provided
in Table 4. A Duncan's range test was performed
(Significant differences are indicated in Table 4) on
the data. The results of this test indicated that all
three groups differed significantly from one another
with reSpect to anterior turn frequency, and that the
random reSponse group did ;not differ significantly from
the posterior stimulation group, whereas it did from
the other two site of stimulation groups.

The type of turns (away or toward) made by the
anterior stimulation group for each block of trials is
shown in Figure 3. An analysis of variance (summaries
are in Appendix Tables II:3 and II:4) was performed on
turns away and on turns toward. Both analyses showed
significant effects (p < .01 for both types of responses)
of trial blocks on turn frequency. Means, standard
deviations and differences between means are presented
in Tables 5 and 6. Duncan's range tests (significant
differences are indicated in Tables 5 and 6) indicate
that the difference between the high frequency of turns
for the first block and the low frequency of turns for
the last block for turns away are significantly different.
In contrast, this is not the case for turns toward, rather,
for turns toward, the frequency of turns in the first

block of trials is significantly lower than the remaining

33

 

 

 

 

9.»
...—.... turns away from
the stimulus
8 - o-----o turns toward the
stimulus
7-
6.
>.
S
(D 5 -
s
0'
23
e4 _
o \
g \
x
8.3 - ~-
(an) ‘ v---.
a: ” .-
2 ' ”
I
I
I
1 ’ .1
L n l l A
I II III IV V

Trial Block

Figure 3.--Turns toward and turns away from an anteriorly

applied test stimulus (Experiment 2) as a function of blocks
of ten trials.

34

Table 5. Means, standard deviations, and differences
between means for turns away from the stimulus in
Experiment II for each block of trials.

 

Trial block I II III IV V
Mean 8.3 4.6 2.9 2.7 1.7
S. D. 1.19 2.69 2.17 2.69 2.59

 

Trial block
I 8.3
II 4.6 3.7

III 2.9 5.4 1.7

IV 2.7 5.6 1.9 .2

V 7.7 6.6 2.9 1.2 1.0

 

 

*p < .05

35

Table 6. Means, standard deviations, and differences
between means for turns toward the stimulus in
Experiment II for each block of trials.

 

 

 

Trial Block I II III IV V
Mean .7 2.9 4.1 2.4 2.5
S. D. .64 1.45 2.41 1.50 2.11

 

 

Trial Block
I .7
II 2.9 2.2*

III 4.1 3.4* 1.2

 

 

IV 2.4 1.7* .5 1.7
V 2.5 1.8* .4 1.6+ .1
*p < .05

+ very near p (.05

36

blocks of trials.

Discussion

 

The results of Experiment 2 have demonstrated that
the type of response elicited by tactile stimulation
depends upon the site of stimulation. This supports
the hypothesis raised at the beginning of Experiment 2
in order to account for the failure of Experiment 1 to
replicate the findings of the pilot study; in the pilot
study the site of stimulation probably varied from the
posterior to the medial section of the subject, giving
rise to a higher incidence of turns than was the case
for Experiment 1 where only the posterior tip was
touched due to the better stimulus control achieved by
the modification of the test stimulus for Experiment 1.
Experiment 2 also generates a second conclusion:

2. tigrina is differentially sensitive to the location
of tactile stimulation, an observation which does not
seem to appear in the literature.

Analysis of the data for the anterior stimulation
group suggests that repeated stimulation to the anterior
end, in contrast to repeated stimulation to the posterior,
produces a more complex response change. A response
decrement in turns away occurs, accompanied by an
increment in turns toward (had the trials been extended
further, from the appearance of the function for turns

toward in Figure 3, one would expect to find a decrement

37
in this response). Pearl (1903) has observed that

strong stimuli elicit withdrawal responses in planaria
whereas weak stimuli elicit approach responses. In

line with this generalization, the results of Experiment
2 may be interpreted thusly: Repeated stimulation with
a strong stimulus creates conditions whereby the strong
stimulus becomes functionally a weak one. This accounts
for the change in response topography observed in the
anterior stimulation group of Experiment 2. Some modi-
fication of Pearl's (1903) generalization, is however,
forced by a consideration of the results of Experiment
1. Any turns observed during posterior stimulation

may be considered to be random turns so that the only
response (if at all) to posterior stimulation is a
posterior contraction which is essentially a withdrawal
response. If the hypothesis (as a result of repeated
stimulation a strong stimulus becomes functionally a
weak one) raised above is correct, then one may conclude
that a strong posterior tactile stimulus serves the

same function as a weak posterior tactile stimulus.
Additional research may reveal that D. tigrina will

give withdrawal responses to both weak and strong stimuli,
making Pearl's (1903) generalization less broad. It is
not within the sc0pe of the present paper to pursue these

matters further.

EXPERIMENT THREE: THE EFFECTS OF REPEATED
STIMULATION: RETENTION TESTS

Information regarding the span of the retention of
the effects of repeated stimulation has been examined
much less often than the occurrence of a response
decrement. Rushforth has demonstrated retention in
Hydra pirardi for four hours; Walter (1908) found that
D. gonocephala and Q. maculata recover response (cessa-
tion of locomotion) to rotation within one minute;
Miller and Mahaffy (1930) have reported recovery from
habituation to a shadow within one minute for the
Trematode Cercaria hamata; and Gardner (1966) has
reported retention of habituation to vibration in the
earthworm for an interval of 96 hours.

It is tempting to suggest (Gardner, 1966) a phylo-
genetic trend in the retention period of the effects of
repeated stimulation; however, short intervals may not
be characteristic of planaria. Whereas Walter (1908)
found full recovery in less than a minute for the
response to rotation, Westerman (1963) has found some
retention of a response decrement to light by planaria
for a five day period. Westerman's (I963) procedure,
however, utilized a distributed presentation of the
light over the five day period; this practice makes it
difficult to compare his results with other studies of
habituation which ordinarily do not use distributive

"practice."

38

39

The present experiment was designed to examine the

retention interval of the effects of repeated stimulation.
Method

Subjects. 40 D. tigrina as described in Experiment
1 were divided into 4 groups (1 minute, 1 hour, 24 hours,
and 96 hours retention interval groups).

Apparatus and Procedure. The procedure was the
same as that utilized in the previous experiments except
as follows: 83 in this experiment were stimulated
medially in the hOpe of gaining more information about
the possible change in topography suggested by the pre-
ceding experiment. The Ss from the various retention
groups were tested alternately. All reSponses previously
described were recorded. During the retention interval,
8 was transferred (except for the 5 minute group which
were retained individually in the test chamber in which
they had been habituated) to a finger bowl until re-
habituation trials were begun. Rehabituation was conduct-
ed in the same manner as the habituation trials had been
conducted. Savings scores were determined by the
formula:

% Savings = H - R
H

Where H = trials to criterion for original habituation;
and R = trials to criterion during rehabituation. When
S had failed to respond 7 times out of 10 consecutive

trials, habituation (or rehabituation) was discontinued.

40
Results

Savings scores as a function of retention interval
are presented in Figure 4. The shape of the curve
resembles that often obtained in studies of retention
of learned responses and compares to retention curves
generated by other studies of habituation (1.2., Gardner,
1966). A Hartley Fmax.-test indicated that the variances
were not significantly different. An analysis of
variance (summarized in Appendix Table 11:5) indicated
a significant effect of retention interval on the
savings scores. Means, standard deviations and dif-
ferences between means are presented in Table 7. A
Duncan's range test was performed on the data (signifi-
cant differences are indicated in Table 7). All groups
were significantly different from the 96 hour group but
not from each other (although the difference between
the 5 minute and 24 hour groups was in the expected
direction and nearly significant - see Table 7).
Pearson Product Moment correlations between habituation
trials to criterion and rehabituation trials to criterion
were determined. The correlation coefficients are
presented in Table 8. None differ significantly from
zero.

The course of habituation for medial stimulation
for various responses (posterior contractions, all
anterior responses, anterior turns and anterior con-

tractions) is shown in Figures 5 and 6. An analysis of

41

as ea

. m
H >popcfl coapnopoh mo coapoczm m we onoom mwsfi>mmun.¢ oesmam

Hm>noch :ofipampom
.pg em

_

.h: H
d

.GHE m

..0H

ION

..0m

.0m

'00

.05

tom

om

 

OOH

.04.

SSutAeg Queo deg

Table 7.

42

Means, standard deviations and differences

between means for retention intervals in Experiment III.

 

 

 

 

Interval 5 min. 1 hr. 24 hr. 96 hr.
Mean 70.7 51.8 44.0 9.2
S. D. 15.96 9.31 40.32 43.29
Interval
5 min. 70.7
1 hr. 51.8 18.9
24 hr. 44:00 2607+ 7.8
96 hr. 9.2 61.5* 42.6’:< 34.8*
::<p< .05

+ almost Sig (diff.é 26.82)

43

Table 8. Correlation coeficients (Pearson's product
moment) between habituation trials and rehabituation
trials to criterion in Experiment III.

 

Retention
Interval ,_5 min. 1 hr. 24 hr. 96 hr.

‘018 ell-Ll- -olI-lp 02].

 

44

variance was performed on each category of responses
(summarized in Appendix Tables II;6 - 11:9). The
analysis revealed a Significant effect of trial block

on posterior contractions but not for the other three
categories. Means, standard deviations and differences
between means for posterior contractions are presented
in Table 9. A Duncan's range test was performed on the
posterior contraction data (significant differences are
indicated in Table 9). Several differences are signif-
icant in the expected direction. The frequency of
posterior contractions from trial block I is Significantly
higher than any of the succeeding trial blocks. Means
and standard deviations for all anterior responses,
anterior turns, and anterior contractions are presented
in tables 10-12, respectively. The data suggest a
differential habituation rate for posterior contractions
and anterior reSponses; the former exhibit a decrement
from the first trial, the latter showed no significant
habituation. Trends in these curves, however, suggest

that additional research might be profitable.

Rehabituation curves are shown in Figures 7—8.
This data was not analyzed because of difficulties
created by the trials to criterion approach which was

used in this experiment to obtain the retention data.

45

6
F c
o——o posterior
contractions
.- - - -o all anterior
5' responses
4

Frequency
I

Response

 

 

n l L .L
I II III IV V
Trial Block

 

Figure 5.--Posterior and anterior responses as a
function of blocks of ten trials in Experiment 33
Figures in parentheses indicate the number of 33
remaining in the sample,i.g.,those 83 which have
not met criterion. When not indicated, n is 40.

46

——-o anterior turns
an"... anterior contractions

>.
03».
c
o
s
0*
Q)
p
[1.
@2-
m
a
o
9.
m
o
a:
1. .

 

 

I l I I j

I II III IV V
Trial Block

Figure 6.--Anterior turns and anterior contractions as
functions of blocks of ten trials for Experiment 3.
Numbers in parentheses represent the number of 33
remaining in the sample,i.g., the number of 88 not
meeting criterion.

Table 9.

47

leans, standard deviations, and differences

between means for trial blocks of posterior contractions
in Experiment III.

 

 

 

 

 

Trial Block I II III IV V
Mean 5.95 4.18 2.80 1.90 1.68
S. D. 2.24 1.69 1.19 1.73 1.57
N 40 40 40 31 19
Trial Block

I 5.95

11 4.18 1.77*

111 2.80 3.15* 1.38

IV 1.90 4.05::< 2.28* 0.9

V 1.68 4.27* 2.5* 1.12 0.22

 

 

*p < .05

48

Table 10. Means and standard deviations for trial
blocks of all anterior responses in Experiment III.

 

 

 

 

Trial Block I II III IV V
Mean I 3.3 3.85 3.1. 3.2 3.1
S. D. 1.69 2.09 1.67 1.82 1.81
N 40 4O 4O 31 19

 

 

Table 11. Means and standard deviations for trial
blocks of anterior turns in Experiment III.

 

 

 

 

Trial Block I II III IV V
Mean 2.3 2.75 2.55 2.22 1.90
S. D. 1.66 1.58 .77 1.53 2.24

 

N 40 40 40 31 19

 

 

Table 12.

49

Means and standard deviations for trial

blocks of anterior contractions in Experiment III.

 

Trial Block
Mean

S. D.

N

 

1.55
1.20

40

II III IV V
1.75 1.3 1.19 1.05
1.30 1.45 1.28 1.22
40 40 31 19

 

50

Discussion

 

Retention of habituation to a tactile stimulus,
when all reSponses are considered, appears to persist
longer than 24 hours but less than 96 hours. Scores
for reSponse components were not considered separately,
rather total scores involving both anterior and posterior
responses were used. The extreme variability of the
component scores led to their rejection. The correla-
tion coeficients (see Table 8) between total habituation
scores and rehabituation scores indicates the low
reliability of rehabituation. This may be due partially
to the procedure. The posterior stimulation data of
Experiment 1 and the anterior stimulation data of
Experiment 2 appears, upon inspection, to be less
variable than the medial stimulation data. This would
suggest that a future attempt to replicate Experiment 3
but using posterior or anterior stimulation would be more
successful in providing reliable data. One other source
of unreliability may derive from differential starvation
periods within the retention intervals. Time since
last feeding may increase or decrease the extent of
differences between individuals or within individuals.
These effects have not been studied and should be examin-
ed before further research is conducted. Another source
‘of unreliability might arise from the difficulty in
stimulating the same area during medial stimulation as

compared to anterior or posterior stimulation because of

51

the change in the configuration of the subject's body
while it is moving. Between individual variation may
have been caused by the width of the subject's body.

The impression was obtained that thicker subjects tended
to make more anterior contractions than turns.

If posterior and anterior responses are considered
separately, Experiment 3 suggests that (1) posterior
responses Show a different habituation course than do
anterior reSponses (the former showing a decrement
from the beginning, the latter not exhibiting a
significant decrement) and (2) anterior turns and
anterior contractions (other anterior responses - head
waving and cessation of locomotion - did not occur with
sufficient frequency to analyze) appear to have the
same form (see Figure 6). It is possible, then, that
both anterior turns and contractions are equivalent
responses. No anterior contractions were observed
with anterior stimulation in Experiment 2. Hyman (1951)
indicates that tactile receptors (hairlike projections
which tend to cluster at the sides of the body) are
densest near the anterior and diminish in number toward
the posterior; thus contractions may reflect difficulty
in stimulus localization for the subject when the stimulus
is applied at the medial region.

Examination of Figures 7—8 gives one the impression
that the shorter the retention interval, the more

closely the rehabituation function resembles the last

52

.cowhmpweU weapoos

no: mm mo gonads esp ..Mxfl.oamsmm on» :a mcwnflmth mm mo popes: esp opmoflpafi
mmmonpcmpmd ca meanesz .m pcosapoaxm ca coammSpHnmnma new coflpmSpHnmn pom manage
cop mo mxooan mo chflpQSSM mm macapomEpcoo sownomeQ mo :omHemdsoonn.h mpdwam

 

      

 

coflpmSpHpmnom soflpmSpflnmm
xooam awake xooam HMflHB
> >H HMH HH HH > >H HHH HH H
J S a d d J 4 d d u
Amflcv cl
fl
:1: .z/ ... H 1 H
l.N .1 Nnd
%
d
0
U
S
l. m .. mm
3-5 m
.b
n
m.
... a 1 an
Uopmoapcw unexpogpo
no: open: oanc m
.h: 00 .Illllll. m
..Hn INN ollllo
0H: H III. ‘0 i 0
as A file

 

53

.oHdEmm on» Ca mcflcflmsma mm mo access can mpmoflpcfl
momonCoamd CH memessz .m pcoefiaodxm :H soapmdpflnmgoe use coaumdpwnmn pom
manage cop mo mxooan mo mcofipocsm mm noncommoe noflpopcm mo comaemdsooul.m madman

 

coflpmdpfinmnom :oaumSpanmm
xooam Hmwhe xooam Heaps
> >H HHH HH H > >H HHH HH H
q . u . u a u m .q .
$1: H H
L
H o 1
a 5 .
mad
I N l %
.d
o
u
S
me

    

Ja
J

popmoapcfi omfispozpo o .m
no: can: OH H: II. lam

u

.... a ll. .. seas . m

.uz am cllunlo
..E H cult-l

.fis m 1

 

 

54

trials of the habituation function, i.e., the first
rehabituation trials for the shorter retention intervals
appear as if one were coming on the scene in the middle
of habituation. This is true of both posterior response
frequencies and anterior response frequencies.

The results of Experiment III generally indicate
the necessity of identifying the sources of noise before

additional research is contemplated.

EXPERIMENT IV: THE EFFECT OF CONCURRENT
STIMULATION

During the pilot study a few subjects were stimulat-
ed with the tactile stimulus in the presence of high
illumination. The presence of the latter seemed to in-
crease the Speed of habituation.t For this reason, the
data of Experiments 1, 2, and 3 were collected under a
very low level of illumination so that the course of
habituation might be extended long enough for study.
The effects of changes in concurrent stimulation have
not often been studied. The few which have, however,
indicate a variety of effects with a variety of situa-
tions. VanDeventer and Ratner (1964) have found that
responsiveness to light decreases in containers which
provide maximum body contact. Ratner and Gardner (1967)
report the same effect for the earthworm, Lumbricus
terrestris. Ratner and VanDeventer (1965) have also
found that occasional rheotactic stimulation induces a
greater responsiveness to light in Q. tigrina. Gee
(1912) has noted that hunger in the leech is associated
with repeated responses to stimulation and a full crop
is associated with positive thigmotaxis and a negative
response to light. The present Experiment was thus
designated to assess the effects of concurrent stimula-
tion, yi§., high illumination, on responsiveness to a

tactile stimulus.

55

56

Method
Subjects. 10 Q. tigrina as described in Experiment
1 were used and compared with data from Experiment 1 (as
it were, subjects in the present Experiment were run
alternately with those of Experiment 1).

Apparatus and Procedure. The procedure was the

 

same as that followed in Experiment 1 (posterior stimu-
lation) except as follows: When the Us were introduced
into the test chamber, a 100 watt bulb, which was
suspended 8 inches above the test chamber, was turned
on. The light remained on for the duration of the
habituation procedure. A glass dish filled with water
was placed between the bulb and the test chamber to
act as a heat filter. Trials to criterion (S's failure
to respond 7 out of 10 consecutive trials) were recorded..
Results and Discussion

Means, standard deviations and differences between
mean frequencies of reSponse for the high illumination
group of Experiment 4 and the low illumination group of
‘ Experiment 1 are presented in Table 13. An F-test
indicated that there was no significant difference
between the variances of the two distributions. A t-
test was performed on the difference between the two
means. The difference was significant (t=3.93,
p < .0005). It may be concluded that habituation to a ‘
tactile stimulus for dark adapted D. tigrina is much

more rapid under conditions of high illumination than is

57

.oHus .emsmeaesa no: case

.:oH:opfl:o w:fipoos no: mm mo popes: on» opmowp:fl momm:p:o:mm :fi mannedz
.H p:oEH:mdxm Eonm we mum: xnmp on» :a :oapflasswpm .a p:osaammxm :fl
mamfihp :op mo mxooan mo :oapo::m m mm :oflpwasefipm pnmfia p:o:::o:oo
p:o:pa3 p:m :pfls mpothSm now m:oapom:p:oo :oa:opmomun.0 onswam

xooam HMflpe

 

 

 

H> > >H HHH HH H
q a . T 1 q A L;
H
l
a. N
1 MN
I .2
m
S
I
pzmaa Ewe p:o:::o:Oo Is
:33 :oapmasefipm mafipompltlul II I o
pnwfla unwann p:m:::o:oo I
:33 :oapmassflum mHHpomp I II
_I
I. L N.

esuodseg

Aouenbedg

58

Table 13. Means, standard deviations and differences
between means for tactile stimulation with and without
concurrent light stimulation, low illumination data
from Experiment I.

 

 

Trials to criterion

Group low illumination high illumination
Mean 44.9 21.7
S. D. 15.38 21.22
N 10 10

Group
Low
illum. 44.9
High
illum. 21.7 23,2*

 

 

*p < .0005

59
habituation under conditions of low illumination. Several
explanations are plausible at this time. Since the sub-
jects were dark adapted prior to administering both the
tactile stimulation and the high level of illumination,
it may have been that the light was the center of
"attention" for the subject, 1.2., the light stimulation
may have blocked other sensory inputs. Were this the
case, light adapted 83 would show little or no difference
under either illumination condition during habituation.
On the other hand, it is possible that the visual input
may be functionally equivalent to the tactile input with
respect to whatever occurs during habituation. In this
case, light adapted 83 would probably habituate more
rapidly when tested in the dark and certainly when tested
in the light. In addition, habituation to light should
generalize to tactile stimulation. It is not within the
scope of the present paper to pursue these questions
further at the moment. Preliminary research underway
indicates that this latter hypothesis is probably incor-
rect; there does not appear to be any generalization
from tactile habituation to light stimulation (and if
the hypothesis were correct there should be reciprocal
generalization). Inspection of Figure 9, which shows
the functions obtained with the two groups, gives more
support to the first hypothesis suggested. If the
concurrent stimulation were dominating Ss "attention"

then we would expect the ends of both curves to resemble

60

each other as the S habituates to the strong stimulus.
In Figure 9, the High illumination group shows a rapid
drop in the beginning and then begins to parallel the
low illumination group.

The findings of Experiment 4 support the previous
findings of the effects of concurrent stimulation on

response levels.

SUMMARY AND CONCLUSIONS

The primary aims of the present study were to
explore the possibilities of the use of planaria in
the study of habituation and, if this were plausible,
to identify those sense modalities which might be most
useful to meet the task of answering questions concern-
ing habituation. A more general aim was to draw
attention to the weakness of defining habituation as a
response decrement and unnecessarily tying it to the
concept of learning. Generally speaking, the results
of the present study encourage the continued use of
planaria for this task with some reservations. The
poor reliability of the data in Experiment III suggests
that some noise is associated with the procedure, at
least with the use of medial stimulation. If this can
be identified and controlled, the animals would lend
themselves to further research concerning the effects
of repeated stimulation. That the noise occurred was
not altogether surprising if one is familiar with the
literature on conditioning in planaria where a con-
siderable amount of variation occurs not only between
investigators but also within studies. A study is
currently being undertaken to clarify some of these
issues.

The more important findings may be summarized:
(1) a clear response decrement to tactile stimulation

occurs in 2. ti rina; (2) both sensory adaptation and

61

62

"fatigue" have been adequately ruled out; (3) reSponse
t0pography may change during the course of habituation
(future research should not use a trials to criterion
technique when examining this particular aspect of
behavior); (4) response t0pography does change as a
function of site of stimulation; (5) habituation is
retained for more than 24 hours but less than 96 hours;
(6) no permanent effects after 96 hours are indicated;
(7) and concurrent stimulation (high background illumi-
nation) increases the Speed of response decrement to

repeated tactile stimulation.

REFERENCES

Bakan, P., Belton, J.A. and Toth, J.C. Extraversion-
Introversion and decrement in an auditory vigilance
task. In Buckner, D.N. and McGrath, J.J., (Eds.),
Vigilance: ‘1 Symposium, N.Y.; McGraw-Hill, 1963.

Beauchamp, R.S.A. The rate of movement of Planaria
alpina. ‘1. Exp. Biol., 1935, 1g, 271-2 5.

Best, J.B. and Rubenstein, 1. Environmental
familiarity and feeding in a planarian. Science,

1962 . 122. 916-918.

Denny, M.R. Research in Learning and erformance. In
Stevens, H.A. and Heber, R. (Eds. , Mental
Retardation. Chicago: University of Chicago
Press, 1964

 

Dilk, F. Ausbildung von Assoziationen bei Planaria
gpngcephala. ;. vergl. Physiol., 1937, 25,
47‘ 2-

Frank, P. PhiIOSOphy g1 Science. New Jersey: Prentice-
Hall, 1957

 

Gardner, L.E. Habituation in the earthworm: retention
and over-habituation. Unpublished PhD thesis,
Michigan State University, East Lansing, Michigan,

1966

Gee, W. The behavior of leeches with especial reference
to its modifiability. Univ. Calif. Pub. 2001.,
1913. 2» 197-305.

Halas, E.S., James, R.L. and Stone, L.A., Types of
responses elicited in planaria by light. g, Comp.
Physiol. Psychol., 1961, 24, 302-305.

Harris, J.D. Habituatory response decrement in the
intact organism. Psych. Bull., 1943. 4Q,
BBS-[F220

 

Hyman, L.H. The Invertebrates, Vol. II. N.Y.;
McGraw-Hill, 1951.

 

Kimble, G.A. Hilgard (sic) and Marquis' Conditioning
and Learning. N.Y.: Appleton-Century-Crofts, 1961

Maltzman, I. and Raskin, D.C. Effects of individual
differences in the orienting reflex on conditioning
and complex processes. 1, Exp. Res. Person.,

1965 . 1. 1-16.
63

64

Mast, S.0. Reactions to temperature changes in
spirillum, hydra, and freshwater planarians,
_A_I_n_0 it Ph!SiOlo , 1903 , _]_._0_, 165-1900

Nagel, E. The Structure 91 Science. N.Y.: Harcourt,
Brace and World, 1961

 

Olmsted, J.M.D. GeotrOpism in Planaria maculata.
1. Anim. Behav., 1917, 1, —81-86.

 

Parker, G.H. and Burnett, F.L. The reactions of
planarians, with and without eyes, to light.
Ag. 1. Physiol., 1901,‘2, 373-385.

Pearl, R. The movements and reactions of fresh-water
planarians. Quart. 1. Micro. Sci., 1903, 46,
509-7119}.

Ratner, S.C. Annelid learning: a critical review.
In Corning, w.c. and Ratner, S.C. (Eds.).
Chemistry of Learning, N.Y.: Plenum Press, 1967.

 

Ratner, S.C. and Gardner, L.E. Studies of the behavior
of earthworms. In A. Stokes (Ed.), Laboratopy
Manual 91 Animal Behavior. San Francisco, Calif.:
W. H. Freeman, 1967.

 

 

Ratner, 8.0. and VanDeventer, J.M. The effects of
water current on responses of planaria to light.
1. Comp. Physiol. Psychol., 1965, 60, 135-139.

Rushforth, N.B. Behavioral studies of the Coelenterate
Hydra pirardi Brien. Anim. Behav. Supp. 1, 1965.

 

 

Shafer, J.M. and Corman, C.O. ReSponse of planaria to
shock. 1. Comp. Physiol. Psychol., 1963, 26,
601‘603 0

Thompson, R. and McConnell, J.V. Classical conditioning
in the planarian, Dugesia dorotocephala. 1, Comp.

Physiol. Psychol., 1955. &§, 65-68.

Thompson, R.F. and Spencer, W.A. Habituation: A
model phenomenon for the study of neuronal
sgbstrates of behavior. Psych. Rev., 1966, 13,
1 “1+3.

 

Thorpe, W.H. Learning and Instinct (2nd Ed.). Cambridge:
Harvard Univ. Press, 1963.

 

VanDeventer, J.M. Regeneration and retention in the
planarian, Dugesia tigrina. Unpublished MA thesis,
Bradley University, Peoria, Illinois, 1960.

 

65

VanDeventer, J.M. The effects of environmental con-
tamination on the frequency of reSponse to light
of two Species of planaria. Mich. Psychologist,
1963, 22, 3 (Abstract).

VanDeventer, J.M. and Ratner, S.C. Variables affecting
the frequency of response of planaria to light.
J. Comp. Physiol. Psychol., 1964, 21, 407-411.

Walter, H.E. Reactions of planaria to light. 1. Exp.
2661., 1907, 5, 35-162.

Wendt, G.R. Vestibular functions. In Stevens, S.S.
(Ed.), Handbook 91 Experimental Psyphology, N.Y.:
Wiley, 1951.

 

Westerman, R.A. Somatic inheritance of habituation of
responses to light in planarians, Science, 1963,

liq, 676‘677 o

Wulzen, R. Some chemotropic and feeding reactions of
Planaria maculata. Biol. Bull., 1916, 33, 67-69.

 

 

APPENDIX I

66

67

.OHHz

.vmpgmvmupstH ohm mm .H >659m pOHHQ mo mpHSmmp mmHmep cop mo mxooap
mo :OHpondm m mm pnwfia 0p oncommmh cfi mandp 6:6 mGOfipomppcooll.HuH mpsmfim

xoofim Hanna
> >H HHH HH H

I

  

  

mCOHPOMLPGOO I

 

N
esuodseg

m

4-
Aouenbng

68

.oauz
.mamwpp amp mo mxooan mo coapoc5m m mm pnwfia op mmcoamoh ca maps» bum
mcoflpomgpsoo .osopw Umpmmvmnxpmu “H >USpm poaflm mo mpasmwmnn.mnH mhdwfim

xooam Hanna
> >H HHH HH H

 

 

I.H
I.N
H
8
S
d
0
«mm
mCOHpOMMPGOo OIIIIO 8
may: I d
9 J
1%
n
8
U
0
..A
aim
10
Ln

 

69

.oan .UmUSHocH ma
msonw mmcoomop Eoncmu < .mamfinp amp mo mxooan mo soapoczm m mm xoonm op

oncommop :fi mGQSp 62m mCOflpomnpcoo .N hUSpm poaflo mo mpazmomln.muH mpdwflm

xooam Hanna

HH H
4.11:1... .wns::‘.dfl.-unn-ur-nanuanv

 

     

.'
\\‘. ’l'l'

oz
esuodseg

."'l'|‘.

mCOflpomppcoo .msopw Eovcmp
mcpzp .msopw Sousa...” I

maps.» .xoonm quill:

mcofipomLQGOU .onzm clllllb

1
M
Aouenbeag

 

7O

. muz
mmcommmp 2p

.mawflpp cop mo mxooan mo coapocsm m mm cofipmadefipm mHHpQMp op
mQLSp 6cm mCOppoohpcoo .m >65pm poawm mo mpHSmmmnn.dnH mhdwfim

xoopm Hmpnp

 

 

 

.Dmflmflm H> > >H HHH HH H
_ _ . p _ . .xz
\
\\
a! \‘II \o\ l H
\ N
I‘ l

J mwa
S
d
O
u
l .JMW
J...
1 mm
b
n
e
u
0
1 or“

mFHSp pulling N.

mCOHPOMHPCOU I

 

APPENDIX 11

71

72

Table 11:1 Summary of the analysis of variance of
trial block scores for posterior contractions in
Experiment I.

 

 

 

 

 

 

Source 33 df MS F
Trial Block 126.6 6 21.1 5.85*
error 199.5 55 3.62
total 326.1 61

*Sig. p.<: .001
Table 11:2 Summary of the analysis of variance of
locus of stimulation scores in Experiment 11.
Source SS df MS F
locus 5039.27 3 1679.76 49.8*
error 1212.70 36 33.69
total 6251.97 39

*p < .01

Table II:3 Summary of the analysis of variance of
trial block scores for turns away from the stimulus
in ExperimentIL

 

 

Source SS df MS F
Trial Block 270.32 4 67.58 11:15*
error 272.60 #5 6.06

total 542.92 49

 

21>< .01

{'1 ’&A\AV.FTRI‘ '_ u)"'_"n . _

 

lo' Elm

73

Table 11:4 Summary of the analysis of variance of
trial block scores for turns toward the stimulus in
Experiment 11.

 

 

 

Source SS df MS F
Trial Block 108.08 4 27,05 8.16*
error 148.80 45 3.31
total 256.88 49

*p < .01

Table 11:5 Summary of the analysis of variance of
the retention interval in Experiment 111.

 

 

 

Source SS df MS F
Trial Block 79847.47 3 26615.82 24.8*
error 38419.30 36 1067.21
total 118266.77 39

*p < .001

Table 11:6 Summary of the analysis of variance of
trial block scores for posterior contractions in
Experiment 111.

 

 

Source 83 df MS F
Trial BlOCk 236.175 4+ 59.03 14.65;:
error 664.895 165 4.03

total 901.01 169

 

*p < .01

74

Table 11:7 Summary of the analysis of variance of
trial block scores for all anterior responses in
Experiment 111.

 

 

Source SS df MS F

Trial Block 12.6 4 3.15 0.71

error 726.2 165 4.4 T”
total 738.8 169 3

 

La

Table 11:8 Summary of the analysis of variance of
trial block scores for anterior turns in Experiment 111.

 

 

 

Trial Block 11.4 4 2.85 1.18
error 396.0 165 2.4
total 407.4 169

 

Table 11:9 Summary of the analysis of variance of
trial block scores for anterior contractions in
Experiment 111.

 

 

Source SS df MS F
Trial Block 10.05 4 2.51 1.4
error 280.3 165 1.7

total 290.35 169