WC? 0? MSTREEUWON C'F ENSflQTéQPfi T4ML$ GM T'HE :‘AAGMTLEDE mg: ESTEMTEQN OF THE KINESTHET‘EC fiWERuEF. EST Thesis in: i‘he. Enema (:5 M. A; MECWGAN S’E‘A‘FE Ufél’ts‘ERS—‘JTY Dame: 2. With-{$6}: 3923?. LIBRARY Michigan State University EFFECT OF DISTRIBUTION OF INSPECTION TRIALS ON THE MAGNITUDE AND RETENTION OF THE KINESTHETIC AFTERAEFFECT By Duane L. Varble A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department; of Psychology 1961 Signed $M {EJA'W (Advisory ABSTRACT EFFECT OF DISTRIBUTION OF INSPECTION TRIALS ON THE MAGNITUDE AND RETENTION OF THE KINESTHETIC AFTERAEFFECT by Duane L. Varble This eXperiment was an attempt to formulate and test certain expectations which were derived from two contrasting positions: (1) that KAE is a learning type phenomenon and that satiation is a neural change similar to a memory trace, and (2) that KAE is produced by a process similar to or synonymous with reactive in- hibition. The derived expectations were based on the assumptions that massed versus spaced inspection trials would lead to different results in the size of KAE. It was further assumed that the re- tention of KAE would be affected in different'ways by the distrin bution of inspection trials. To test the derived expectations, the following experiment was designed. Six groups each consisting of 19 subjects were in" dividually tested for KAE. Each subject made judgments of the equality of widths of two blocks of WOOdo These judgments were made in series of four immediately before the inspection period (pre-test), immediately'after the inspection period (postmtest), and after a specified amount of time had elapsed since inapecm tion (retest)o Duane L. Varble All subjects received 16 thirtyhsecond inspection trials. For half the subjects these trials were massed, and for the other half the trials were spaced. Then one of’the massed inspection groups and one of the spaced groups each returned for retesting after intervals of either 15.minutes, 2h hours or 7 days. The difference scores between the pre-test and post-test PSE's were the immediate KAE's. The difference scores between the pre—test and the retest PSE's as well as the difference be- tween the post-test and retest PSE's were used as measures of retention after-effects. A t-test and two analysis of variance designs using these difference scores attempted to test the above mentioned expecta- tions. None of these tests were statistically significant, and thus, the basic question as to whether KAE's are produced by a learning type phenomenon (memory traces) or by reactive inhibi— tion could not conclusively be answered,but the evidence was in favor of the learning type explanation. The following results were obtained: 1. Distributing the inspection trials had no significant effect on the size or persistence of KAE's. 2. A total of eight minutes of inspection established rela- tively large KAE's which did not decrease in size after an interval of a week. This 1351:: contrast to the persistence of most visual after-effects. Also, there is an indication that KAE's are a Duane L. Varble specific experience which is not affected by ordinary day to day use of the hands. 3. A correlation of .51 was obtained between the imnediate after-effects and the retention after-effects. Stability co-effi- cients for this relationship indicated that KAE's are most stable after 15 minutes but could be reliably obtained after intervals of 24 hours or 7 days. 4. Negative correlation coefficients of -.A7 and -.51 were obtained between the size of the pre-inspection PSE and the size of the immediate KAE and the retention KAE respectively. This _ meant that subjects with large pre-inspection PSE's tended to have small after-effects. EFFECT OF DISTRIBUTION OF INSPECTION TRIALS ON THE MAGNITUDE AND RETENTION OF THE KINESTHETIC AFTERAEFFECT By Duane L. Varble A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department of Psychology 1961 Acknowledgments I would like to thank the members of my committee, Dr. Donald M. Johnson and Dr. Gerald King, for their help with this thesis. I would especially like to express my gratitude to my committee chairman, Dr. Paul Bakan, for his patience and underb standing as well as his invaluable help with the thesis prOper. I would also like to acknowledge the aid with the statis- tical computation rendered by Gilbert Rothman. Finally, I would like to express my deepest gratitude to my wife, Charle. I am.grateful for her understanding and support when such were needed. Also, I am.indebted to her for the many clerical tasks she willingly performed and which went a long way in making the completion of this thesis possible. To her this thesis is dedicated. Duane L. Varble ii Ishlasiicmissia Introduction Method Subjects Design of Experiment Apparatus Procedure Scoring Results Discussion Summary References iii 16 16 16 l7 19 2h 26 32 37 AO .Table 1 Table 2 Table 3 Table A Table 5 Figure 1 List 9; Tables DeSign Of experiment eooooeooeeoeoeeeeoooo 17 Mean retcnf’cn KAE and standard deviations fire~test—rctest) .e..e..s..oo.. 27 Analysis of variance of reten— tion of KAE (retest minus pre- teSt OOOOOOOOOOOOOOOOOOOCO0000.00.00.00... 27 Mean retention KAE and standard deviations (post-test-retest) ............ 29 Analysis of variance of reten- tion KAE (post-test minus reteSt)00.OCOOOOOOOO0.000.000.00000.0.09.0 29 Diagram Of the apparatus ooooooeeeoooeooee 20 iv 1. Introduction An after-effect is the distortion or displacement of a percep- tion which occurs after exposure to an inspection stimulus. It is usually manifested by a difference between perception of a standard stimulus before and after exposure to an inspection stimulus. After-effects are not restricted to any particular sense modality. Visual after-effects were the first to be studied, and much of the work on after-effects has been concerned with the visual effects. Gibson (1933) discovered the first visual figural after- effect in 1933. This was caused by the wearing of prisms over the eyes. The after-effect occurred in the form of displacement of vertical lines when he removed the prisms. He called this phenome- non "adaptation after-effect" and conducted formal experiments to prove that after-effects could be produced without the use of prisms. Gibson and Radner (1937) later studied after-effects in both the visual and kinesthetic modalities. Kbhler and wallach (194A) found after-effects in patterned vision and postulated a theory of neural satiation to explain after-effects in general. Kohler and Emery (19h?) found visual after-effects in the third dimension. Auditory after-effects have been obtained by several investigators. Deutsch (1951) studied AE using pitch. Jones and Bressler (1949) studied the displacement after-effect in auditory localization and KrauskOpf (1954) found after—effects in auditory space. 2. After-effects have consistently been obtained in the kines- thetic modality. Since the present experiment was concerned with kinesthetic after-effects (KAE), the research in this area will be reviewed more extensively. The classical study of KAE was done by K8hler and Dinnerstein (19A?) and published in 1947. They found that Gibson' 3 "adapta- tion after-effect" or "after-curvature" could reliably be obtained in kinesthesis but could not be easily measured. After some explor- ation, thler and Dinnerstein found that afterueffects could be obtained by using judgments of width. They had blindfolded subjects judge the width of a standard sized block held in one hand by using the other hand to find a point of equal width on a second variable sized block. The subjects then "inspected" a third block, either wider or narrower than the standard block. The inspection consisted of rubbing the inspection block with the hand that held the standard block before inspection. Then, when the subjects made judgments of the equality of the widths, as they had done before inspection, there was a definite tendency for those subjects who had rubbed the narrow inspection block to subsequently'make their judgments of equality wider than they had before inspection. The reverse was true for those subjects who had rubbed the wider inspection block. thler and Dinnerstein called this distortion "kinesthetic after- effect" (KAE).~ It was measured by calculating the difference between the average pre-inspection and post-inspection.judgments. They found 3. large individual differences but consistent after-effects among many individuals. Kohler and Dinnerstein used this technique to study the effects of many of the variables involved in kinesthetic after-effects. After several experiments, they concluded that the important criteria for obtaining an after-effect was that the fingers have tension in them.and that they be held in the same or similar position during the inspection.period. Other investigators have used K8hler and Dinnerstein's ap- paratus and testing procedure to investigate the variables in- volved in kinesthetic afterbeffects. Charles and Duncan (1959) studied the distance gradient in kinesthetic after—effect and found a significant distance gradient of inverted4U shape, i.e., the amount of after-effect first increased, then decreased as the difference between the standard and inspection stimulus increased. Wertheimer (l95h) studied constant errors in the measurement of figural after-effects. He concluded that the preferred hand should always be used to find the PSE on the variable stimulus be~ cause this hand has the smallest Bilateral Kinesthetic Difference (BKD). BKD is defined Operationally'by Wertheimer as the difference between the pre-inspection and post-inspection PSE's. Wertheimer and Leventhal (1958) investigated the effects of varying amounts of satiation (length of inspection periods) on the size of the after-effects. The results showed that the size of the after-effect was positively correlated with the amount of satiation .4. given. Recently, Heinemann (1961) has published a study in which he used standard blocks of various widths and tested daily for 11 days. He found the expected relationship that after inspection, the subjects overestimated the width of the standard blocks that were wider than the inspection block and underestimated the width of the standard blocks that were narrower than the inspection block. No after-effects occurred when the inspection block and the standard blocks were objectively equal. The present paper was primarily concerned with two_variables: l. The spacing of inspection trials. 2. The time interval between the inSpection trials and the retention tests. To study these effects all the inspection trials were given in the initial session. There is very little literature on the effects of massed vs. spaced inspection trials on after-effects. Bakan:L has done some unpublished studies with the spacing variable. He found no signi- ficant difference in size of after-effects between massed vs. spaced conditions. The only other experiment on this variable was an unpublished doctoxal dissertation by Mountjoy (1957). He studied the effects of exposure time and intertrial interval upon rates of decrement *— 1Personal communication 5. in the Mdller—Lyer Illusion. Because only an abstract of this work is available, the details of the experiment cannot be reported. Mountjoy found no significant effects of either the intertrial in- terval or intertrial task variable on the rate of decrement of the M—L Illusion. There has been.more work on the permanence of after-effects. Gibson (1933) reported earlier that his type of visual after-effects tended to persist over a few hours or even days. With regard to kinesthesis, Kohler and Dinnerstein (1947) found that by testing daily over a period of weeks, the pre—inspection.judgments (PSE) and post-inspection judgments (PSE) grew in size. At the same (time, the difference between these two (the after-effect) grew as well. When this data was averaged and plotted over a period of several days, the resulting graphs appeared very similar to the familiar learning curves obtained on such tasks as the pursuit rotor. The fact that the pre-inspection judgments and the after-effects grew suggests that the inspection produced somewhat permanent satiation. This indication 3f permanence was further supported when Kohler and Dinnerstein retested two subjects without giving them.inspection. These subjects showed significant after-effects 3% and 5 months after the last inspection periOd. Later, wertheimer and Leventhal (1958) reported an experiment on the permanence of satiation or after-effects. They gave several subjects 2 minutes of inspection daily for several days, then tested 6. for after~effects bi-monthly. They found after-effects significant at the .05 level of significance as much as 6 months later. For two subjects there were significant after-effects 8 months after the last satiation period. Thus, the effect of distributing the inspection trials has largely been nt.=:g.‘.’;.ected.9 and while the persistence of AE has been studied to some extent, such experiments always included several inspection sessions. This study hOped to investigate these varia- bles simultaneously. To explain the design of the present experi- ment, the theoretical aspects of the problem must be considered. The major theory which may be regarded as an explanation of figural aftermeffects (FAE) is K6hler’s (1944) theory of neural satiation. This theory is presented in detail in the Kohler and Wailach article {lth}. The theory of neural satiation uses the Gestalt concept of psychophysical isomorphism, i.e., the idea that perceptual experience is isomorphic with electrochemical patterns in the cortex or the brain field. The basic postulate is that "inspection" causes a change in the neural tissue. This change occurring in the brain.field is called "satiation" and results in a subsequent alteration of the percept. The change from the preminspection percept to the posteinspection percept is called the afterweffect and is a resultant of a change in brain tissue (satia- tion) induced by the inspection stimulus. There are other theories for explaining figural after-effect (FAE) 7. such as Osgood and Heyer's "statistical hypothesis" (1952). How- ever, these theories have been.much less influential than the sa- tiation theory. An issue in the recent literature on FAB has been concerned with the similarities between "neural satiation" and other concepts. Two concepts in particular have been compared with "neural satia- tion." Duncan (1956), Eysenck (1955) and others have pointed out the similarity between satiation and reactive inhibition. On the other hand, Kbhler and Fishback (1950) have suggested that neural satiation may be a change similar to that underlying memory traces. Reactive inhibition (IR) is Hull's (1943) concept. He has explained the concept as follows: All responses leave behind in the physical struc- tures involved in the evocation, a state or substance which acts directly to inhibit the evocation of the activity in question. The hypothetical inhibitory condition or substance is observable only through its effect upon positive reaction potentials. This nega- tive action is called reactive inhibition. An in— crement of reactive inhibition is assumed to be generated by every repetition of a response whether reinforced or not, and these increments are‘assumed to accumulate except as they spontaneously disinte~ grate with the passage of time. (Hull, 1943) Duncan (1956) was among the first to point out the similari— ties between satiation and IR° While Hull was satisfied with a peripheral interpretation of reactive inhibition, Duncan interpreted the concept in the modern sense as a generalized centrally located phenomena. Duncan reviewed the studies in the literature which 8. demonstrated the similarities between satiation and IR. The two major similarities were in terms of the central locus and similar effects of both IR and satiation. These similarities are best exhibited in the following quotes from Duncan: Kahler and Wallach, and Gibson, have shown that satiation has a central locus by demonstrating that figural after-effects occur when the inspection is presented to one eye and the test-figure to the other eye...Ammons, Grice and Reynolds, Irion, and Gustafson, Kimble and Rockway, have shown that it (IR) is not confined to effectors involved in the response. Therefore, it may be assumed that IR also has a cen- tral locus. (Duncan, 1956, p. 229) Duncan then goes on to show how IR and satiation have the same effects. Both processes have essentially the effect of dis- torting behavior away from some criterion or standard. This is obvious for satiation; the process is inferred from.distortions in the perception of figures. In the case of IR the effect occurs while stimulation is still continuing, e.g., during highly massed practice on a motor task, as measured by a depression of per- formance as compared either to an initial performance level or to performance of S's working under distribu- ted practice...(Duncan, 1956, p. 230) Duncan suggested that satiation and IR may be two names for the same basic process. Eysenck (1955) has also studied the relationship between the production of after-effects and IR° He measured IR in terms of re» miniscence scores and the size of KAE. He was led to conclude that: Phenomena of reminiscence, of’massed and Spaced learning, of vigilance, of blocking, and many n+hers have been interpreted in terms of inhibition. While it remains possible, of course, that in each separate case we must 9. have recourse to a different type of inhibition, this does not seem a likely contingencv and the hypothesis certainly seems worth testing that it is the same type of cortical inhibition which causes all these pheno- mena, as well as the perceptual ones discussed above (KAE‘s). (Eysenck, 1955, p. 103) Rechtschaffen (1958) tested Eysenck's hypothesis using visual after~effects and found no significant correlation between IR or VAE. However, he hesitated to conclude that they are different pro- cesses. Rechtschaffen also reports an unpublished study by Meier (1956) who found a significant negative correlation between the amount of reminiscence on inverted alphabet printing and the am mount of KAE. In Spite of the few indications to the contrary, the similar- ity between satiation and IR appears to be a strong one. If they are the same process, both the size and the retention of KAE should be affected by the distribution of inspection trials. Thus, using the logic of Duncan (1956) and Eysenck (1955), reactive inhibition would temporarily impede learning in the form of acquisition of skills but should facilitate the acquisition of aftermeffect. This follows logically if reactive inhibition, which inhibits learning, and neural satiation, which leads to after-effect, are two names for the same basic process. In contrast to Duncan's and Eysenckis positions is the inter~ pretation of neural satiation suggested by Kohler and Fishback (1950). Kohler and Fishback used the concept of satiation to explain how they experimentally "destroyed" the Muller-Lyer Illusion. Kohler 10. and Fishback felt learning or "practice effect" did not adequately account for the destruction of the illusion. They further postus lated that neural satiation, which presumably did destroy the 11- lusion, was quite similar to memory traces. Of course, memory traces are involved in learning. The reasons for this interpreta- tion are best illustrated by quotes from.K8hler and Fishback's article: Actually, the effect of many experiments in an imme- diate sequence is so strong that, when the illusion has been destroyed, it may be brought back to life again merely by giving a long series of further experiments... Obviously, such observations resemble well-known facts in the field of learning, namely the inhibitions which make it difficult to memorize monotonous series of items, or to establish a precise motor performance in often repeated trials. (Kbhler and Fishback, 1950, p. 339) The ties between learning phenomena and satiation are further strengthened in the following quote: ...not only the obstacle which delays destruction of the MEL Illusion but also the inhibitions which accompany some forms of learning are therefore to a degree reversible. Reminiscence as a certain improve- ment of recall when tests are not given immediately is, of course, merely a special form of the same fact. (Kohler and Fishback, 1950, p. A00) Kbhler and Fishback,thus,equate the inhibitions observed in repetitive learning tasks with the obstacle to satiation therefore to the development of after-effects. For them this obstacle is satiation in the "wrong" places: It follows that during a long rest period satiation in the 'wrong' places can gradually decrease, and that therefore the obstacle can largely disappear, while satiation in the"right' places remains very strong. (Kohler and Fishback, 1950, p. hoz) 11. The decrease of satiation in the "wrong places" after a rest period is equivalent to the decrease of inhibition in learning tasks which, in turn, is responsible for reminiscence. Once the similarity between the obstacles involved in learn- ing experiments and in after-effect experiments was established, Kohler and Fishback speculated about the similarity between memory traces and satiation patterns: we must therefore now ask ourselves how satiation is related to memory...Little is known about memory traces. They are defined by certain operations, such as recogni- tion, recall, and so forth, which they are supposed to explain. But if they are to serve this function, we must ascribe to them at least one fundamental character- istic: to a considerable degree, memory traces must re- semble the processes by which they are established. It is true that sometimes we have reasons to suspect that the traces are defective; but this very expression points to the fact that in many instances the correspondence must be fairly good. As a consequence, the theoretical situation in this field is now as follows. It is as- sumed that the brain processes which go with psycholo- gical events establish memory traces, and that these processes resemble the processes in question. But at the same time these processes form satiation patterns which must also be adequate representations of the pro- cesses. It seems hardly natural to believe that a given process establishes simultaneously two altogether dif- ferent effects in the nervous system.which are both vir- tually pictures of that process. Thus, the question arises whether the two effects, memory traces and satia- tion patterns, can perhaps be identified. But memory traces are only most indirectly defined, while patterns of satiation have now been given an interpretation in fairly specific biOphysioal terms. Under these circume stances, the two concepts can be profitably identified only if the concept which is less well understood is re— duced to the one which is much better defined. Hence, our question muSt actually be whether satiation pat- terns can be assumed to play the part which is commonly attribgted to memory traces. (thler and Fishback, 1950, 13° 1‘05 0 12. After commenting on the persistence of after-effects both in their own studies and others, Kohler and Fishback state: "...According to this evidence, satiation patterns may be per- sistent to a degree which makes them comparable to memory traces in this respect also." (Kohler and Fishback, 1950, p. #07). Finally, after presenting several arguments and demon- strations to show why satiation patterns and memory traces could be the same phenomena, Kbhler and Fishback conclude: "...It seems possible that memory traces are weak patterns of satiation; but at the present time no convincing proof of this thesis can be given." (Kbhler and Fishback, 1950, p. #09). Thus, for K‘dhler and Fishback neural satiation and menory traces are essentially equivalent. For them, reactive inhibition would impede learning or performance in massed practice. At the same time, satiation in the "wrong" places, which is their equiva- lent of I would impede the establishment of figural after-effects R9 under some circumstances. Therefore, the view that neural satiation and reactive inhi- bition are the same process would lead to one set of expectations for figural after-effect. The view that satiation and memory traces are the same would lead to another set of expectations. Such expectations would stem not only from the nature of the views in themselves, but also from what has been observed in learning experiments in the past. 13. As previously mentioned, the decrements in performance during massed practice and reminiscence after a rest period are commonly attributed to the effects of reactive inhibition. AlSO'Well known is the fact that spaced practice is more effective in terms of learning than massed practice. Kimble (196L) cites many examples of this effect. Less well known is the relationship between the distribu- tion of practice and the retention of the material learned. This is exemplified by’a quote from McGeoch and Irion'slghg_Psychology 2;,Human Learning (1952). They state: A number of studies have been concerned with a comp parison of the degrees of retention of materials learned under massed and distributed practice. In general, material learned by distributed practice tends to be retained better than material learned by massed practice, although for short retention intervals and for certain types of learning tasks, exceptions must be made to this general conclusion. (MCGeogh and Irion, 1952, p. 150). The present study was designed around known relationships in the field of learning. The study tested for similar relation- ships in the area of kinesthetic after-effect (KAE). Specifically, the study is concerned with the effects of distribution of inspec- tion trials on the size and retention of kinesthetic after-effects. With the assumption that neural satiation is directly or indirectly the cause of figural after-effects, the view equating satiation with I would lead to expectations contrary to the view R which equates satiation and memory traces. The expected effects of massed vs. spaced inspection trials should be opposed for these opposing views. Specifically, the question becomes: Is the KAE produced by a learning type phenomena analogous to memory traces or is the KAE brought about by reactive inhibition? To answer this question six independent groups of subjects were given an equal number of in- spection trials, tested for immediate KAE, and tested for retention KAE after varying intervals of time. Three of these groups received massed inspection trials, and three received spaced inspection trials. Then, cne of the massed condition groups and one of the spaced condition groups were each tested either 15-minute, 2A-hour or 7-days after the inspection period. This experimental design was an attempt to explore the fol- lowing possibilities: 1. If KAE's are caused by a reactive inhibition type pheno- mena, those groups receiving massed inspection trials should have larger immediate after-effects than the spaced inspection groups. Of course, this assumes IR increases during performance (or in- spection) and dissipates during rest as Hull and others postulate. 2. On the other hand, if KAE's are produced by a learning type phenomena (memory traces), then the groups receiving Spaced inspection trials should have the larger after-effects. 3. For retention afterbeffects, the massed groups may have larger after-effects than the spaced group at the 15 minute retest if IR is the cause. But if reactive inhibition is all that is in- volved, the afterbeffects should decrease in size after 2h hours 15. and be smaller yet after 7 days. Presumably, if a generalized type of IR causes KAE, a 15 minute rest period may not be long enough for the KAE's to diminish substantially when 8 minutes of massed satiation or inspection is used. 1.. Also we would expect the retention after-effects for both inspection conditions to decrease significantly in size after 21. hours and 7 days, if they are produced by memory trace pro- cesses. However, we would expect the after-effects of the spaced inspection groups to be larger than the massed inspection groups at all three retests (15 minutes, 24 hours, 7 days) if a learning phenomenon is involved . 14.2mm Subjects. - The subjects used in this study were students of both sexes enrolled in the introductory psychology course at Michigan State University for the spring term 1961. Each participating subject was given 1 hour research credit as partial fulfillment of a requirement of the psychology course. The subjects varied in age from 17 to 26 years of age. Be; cause of some indication in earlier studies that females had smaller after-effects than males, an attempt was made to balance the number of subjects of each sex in each group. As it turned out, due to unforeseen circumstances, 2 groups contained 7 fe- males and 12 males each, 3 groups contained 6 females and 13 males each, and 1 group contained 5 females and 11+ males. Resign o_i_'_ figerimen . - A total of 111+ S's was divided into 6 groups, each containing 19 subjects. The assignment of 8's to groups was more or less random, though some limitations on randomness were imposed by E's availability for testing only on Monday, Thursday and Friday. Thus, a subject in the groups to be retested 21. hours after the initial test had to be tested initially on a Thursday. Two measures of kinesthetic after-effect (KAE) were taken on each S, a post-inspection measure and a retention measure. The time between these two measures was either 15 minutes, 24 hours, or 7 days. All S's were exposed to an inspection stimulus for a total of 8 minutes, but for half of the S's the exposure was massed (30 second inspection - 2 second rest...). For the other half, the 16. 17. exposure was spaced (30 second inspection - 30 second rest...). The combination of retention and Spacing conditions makes for the 3 X 2 factorial design summarized in Table I which follows. TABLE I Design of Experiment Inspection Time between the post-inspection and the re- Conditions tention measures. ‘ 15 minutes 21. hours 7 days _§_ ..§_ _§_ 1 1 1 2 2 2 Massed 3 3 3 19 19 19 .3. _S- i 1 l l 2 2 2 Spaced 3 3 3 19 19 19 Apparatus. - The apparatus used in this experiment was developed by Bakan. It was similar in principle to the apparatus used by Kohler and Dinnerstein (1947), but it differed from their apparatus mainly in the method of varying the width of the test stimulus. The apparatus consisted of three main parts: a standard stimu- lus in the form of a constant width block, a test stimulus in the 18. form of a variable width block, and an inspection stimulus of fixed width. The standard stimmlus was formed by two pieces of beaver board 1/4 inch thick, 4 inches high and 5 inches long. These two pieces of beaver board were firmly anchored to a base in the vertical position with 1% inches between the outer edge of one piece of board to the outer edge of the second piece of board. Thus, when the subject placed his thumb and forefinger on these outer surfaces, the standard felt like a solid block 1% inches in width. The test stimulus consisted of similar parts except that only one of the pieces of beaver board was solidly anchored to the base in the vertical position. The second piece of beaver board was also in the vertical position but was attached at a right angle to a third piece of beaver board approximately 1/3 inch thick, 3 inches wide, and 6 inches long. This piece lay flat on the base in the horizontal position. These two attached pieces of beaver board were not anchored to the base but slid freely within grooves so that the test stimulus formed by the vertically anchored piece of wood and the vertical sliding piece of wood could vary in 'width. Variations in width were made by moving the sliding piece of wood closer or further away from.the stationary board as desired. To facilitate this movement, an adjustable metal bracket was at— tached to the outside edge of the sliding vertical part of the 19. test stimulus and the outside edge of the standard block. These brackets served as a finger grip by holding the fingers in place. The blindfolded subject placed his forefinger in these finger grips with his thumbs on the opposite side of the block to make a "judge ment" of the subjective equality of width of the two blocks. This was done by moving the sliding part of the test stimulus in or out until that block felt equal in.width to the standard block. The point of subjective equality (PSE) was measured by a 6 inch metal ruler glued to the base of the apparatus with zero starting at the outside edge of the anchored piece of wood with the rest of the ruler extending along the sliding grooves. This ruler was calibrated in units of 1/32 of an inch so that the point of sub- ject equality (PSE) could be measured to the nearest 1/32nd inch. Both the standard block and test block were mounted 18" apart on a beaver board base, 1/L inch thick, 10 inches wide and 24 inches long. (See Figure 1) The inspection.stimu1us consisted of a board of smooth pine 5 inch thick, 2 inches wide, and 6 feet long. This was mounted on a table on the side of the 5's non-pre- ferred hand. Procedure. - 'Each subject was tested individually and did not see the apparatus before or during testing. Upon arrival, the subject was given a "pre-test orientation sheet" to read. The orientation sheet read as follows: (after Figure 1.) 20. 1 . 1 Ar. 1 S Finger ’V . ' Board Grips o <— , f— _ /l '—5 / h. —> 10 O , v M I! I..~.....l T L I f—B‘“ I 21," Standard Stimulus Test Stimulus Figure 1. Test Apparatus Width Test Pre-test Orientation In this experiment you will be asked to judge the equality of widths or thicknesses of two wooden objects. One of these objects is called the constant width object, and you will feel its width by holding it between the thumb and forefinger of your non-preferred hand. (Left hand if you are right handed and vice versa.) The other wooden object is called the variable width object and will be held between the thumb and forefinger of your preferred hand. The forefingers of both hands will be in finger grips, and you will adjuSt the width or thickness of the variable width object to equal the width or thickness of the constant width object. This will be done by moving the forefinger of your preferred hand in or out until the two objects feel equal in width. Further explanation and instructions will be given inside by the experimenter. The apparatus was set up so that the preferred hand was used to manipulate the test block in making judgments. After a brief period, the experimenter obtained information on age, sex, preferred hand, class instructor, and previous participation in similar 21. experiments. (Two other experiments involving kinesthetic after- effects were in progress at the same time, but no subject who had participated in an eXperiment similar to the present experiment was included in the sample.) Then, the subject was blindfolded and led into a room.where the apparatus was set up on two long narrow tables. On one of these tables was the apparatus with the standard stimulus and the test stimulus. The inspection block was placed on the other table. The subject stood between these tables facing the experimenter. With the subject in this position, the experimenter read the first paragraph of the general instructions. The rest of the general in- structions were not read, but they were followed carefully by the experimenter, in order to make certain that everything was covered and that each subject got the same instructions. Instructions for Width Judgment Experiment "This is an experiment in the judgment of widths. we are interested in your perception of the equality of widths of two objects you are about to hold. It is impor- tant that your judgments be based on the feeling of the width of the objects between your fingers. That is why you are blindfolded. If you can see through or under your mask, please tell me now so that I may adjust it for you. Now, I will show you what to do." "This is the constant width. Iill adjust the finger grips to fit the size of your fingers. We like them to be firm.but not tight." (Adjust and check with S's. The first joint of both the thumb and the forefinger should come to the top of the piece of wood in the block.) "Try to put your fingers in exactly this same way each time." "This is the variable width." (Demonstrate how it slides in and out with the S's hand in the finger grips.) 22.. "I want the finger grips to feel the same for both hands. Now your task in this experiment is to adjust the varia- ble width so that it feels equal to the constant width. We've found the best way to make judgments is to go past the equal point and come back to it. You may go either way. Also, press your fingers lightly against the sides of the objects when making your final judgments. We ask you to do this because people have a tendency to relax _ their thumbs and fingers, and then the judgments they V” think they are making are not the ones that show up on : the apparatus. Now lift your hands off the apparatus please." (Set variable width at the starting point. 6 After starting with the first practice judgment and ' ending with the last retest judgment, place the variable width block at 2 inches (descending), then 1 inch (as- cending), another time at 1 inch, then 2 inches so that .- each series of four judgments goes 2, 1, 1, 2 or (DAAD). E "Okay, start here. Tell me when you have finished a judgment." (Put S's hands back in the finger grips after each judgment. After the S makes 1. practice judgments, record the next 1. for the record. Time all judgments for the record.) 'Now, I'm going to have you rub a block of wood be- tween the thumb and forefinger of your (non-dominant) hand. I'll show you where to rub and how fast to rub. Also, I'll tell you when to start and stop rubbing. After you are through rubbing, you will again make judgments of the width of a block of wood as you have been doing. This rubbing will take only a few minutes, but it may seem like a long time. Okay, do it like this." (Show how it is done using long sweeping strokes at approximately 50 traverses per 30 seconds trial.) "Be inc" After rubbing is completed:) "Now I would like you to adjust the variable width so that it feels equal in width to the one in your (non-dominant) hand, right now. Do it as quickly as possible. Most peOple make the judgment in less than 15 seconds. Begin." (Record the first four judgments, then lead the subject back behind the screen and remove the blindfold. Up to the point where the subject rubbed the inspection stimulus, all subjects were treated the same. At this point the subjects receiving massed inspection trials (M—groups) rubbed the block for a total of eight minutes. These eight minutes were broken 23. up into 16 thirty-second inspection periods separated by two-second rest periods. Subjects receiving the spaced inspection trials (S- groups) also rubbed the inspection stimulus for a total of eight minutes, but for these groups the 16 thirty-second trials were separ- ated by thirtybsecond rest periods. During the rest period, the sub- ject relaxed with his hands at his sides. After the inspection per- iod all subjects made four post-inspection judgments in.the same order (DAAD) as the pre-inspection judgments. The subjects in groups 1 (MelS) and 2 (5-15) returned 15 ndnutes after the last post-inspection judgment for retesting. The subjects in groups3 (M—ZA) and A (8-24) returned for retesting 2h hours later. (This time varied from.20 hours to 27 hours, but the greater number of subjects returned between 23 and 25 hours later with 24 hours being the median.) Finally, the subjects in groups 5 (M-7) and 6 (Sn?) returted for retesting after 7 days had elapsed. (Only one subject included in the experiment missed her afternoon appointment and returned a day later for retesting.) The procedure for retesting was very simple. The subject was blindfolded and led to his previous position. Then, the experimenter read the following retest instructions: Retest Instructions "Today," (Use the word "now" for 15 minute groups in- stead of "today.") "you are going to make some more judgments. Again it is important that you make the judgments on the basis of how the objects feel to you now." "Okay, let's get your fingers in the grips like the last time." (Adjust grips and check with S). "Adjust the variable ’\_ I (3&5 0 sv.‘ a -.H a -' ... ”.L ”fixa- . ”-U- . .‘ - H. e. 1.0 t-l'. 'L-w-‘J -:'C!..:.’n..l.. the (3611:: built. will/3'1 1.31 Vina! (Fl.-m.-'»f3.<.ma..7'1;—:f.-.L) 3 r r- v t (hese j ~1gM'ents as quickly and acm .. C :3 €33.33 "when you ha ”6' the L40 aqua, in mini-{.10 .. . . . .. t , -uratel' as you ccn. Take your hands off when you have . ’ ' .t I “Q ‘ .‘I - 1. h ,4 , -- o. . av - V y'- 0" an a I“ . a h- .- wnen the last retest iudgment u 9 completed and recorded, the . 3 z. ' ... ._'~ - ,.._. . -~-.--.1-.. 3. - .,.- 'T-‘dbuf-‘Ct: Wa. is held 13 renews 1.1.5 blind Cl. 0 H6 Vac-Le 96.1.7611 etc-u L0 :15"? the apparatus an. was told :Ln a general ‘ey that rribb.-zg the inspeca 5 £1. ‘14 c *3 :3 CD ‘25 1;. 1—3 I {J U‘ (h ('1 “3 H :3 fl) '3 (D ‘5" (1') m 7" 51 97 w E '1? LJ SD 3': {-3 (c u. “I u I {f I 10 f j .; I-i Va 9 H 3 ‘J E to see if thele was an change in judgments after a lease of time. Scuwiri~ - Each subjectis judgment of equality of the width cf the LWQ.leck.3 (FEE) was rec creed,in whole numbers. The zero pain- - I- -' r \ -:\ w - 6' .1 .\ a. ”I ' _, ‘ 3 Q .-'~ g'. H .3 .3 ' ~t the one in¢.h p0 at on the ruler. Thus, a ~core oz 10 1'. 9- \II IL- (b c V :1 ’ to l and 10/32 inches. A score of 32 2; ( J E- f L t.) C!" (.1.- Ch 0 t? r .50 fl \i" S - ‘q (f "D ’EI S. {b I- .R wccli be equal to 2 inshte and a score of L.O would be equal to P '3 I: i. f} a' a“ -‘-‘ e an- qfig inches, etc. ! AR :3 {II ”V. (D (J e l ( 3 Each subject made L prem specticn judgments, h post«' iwdgmen's, and L r— Tcried juiaments. The mean of each set of fear Vans ‘1‘..de r . v -u a '11‘ -3,_ jTi""tuts *“n ‘ru‘ei a point of subje~tive equality (Pot). for - r) - J each suijeci the differs.-c s between the creuinspect.icn Pan a: d t;e obs! .- - -:.~- .. .- . we“ .. - \3 yes: on Eek was Cdlclldtmdo The d.iferences bewtw sen the . ' ' -~ I‘ L. M“. . '. '4 «A a 0 A -"‘ - - - . ;~..-‘ - n O ‘ -' "“3 -eubmun .3n and the retention Pm were :1. campited. Fi- nell' the differs-”e “tweet the postuinspection Psi and tue reten~ J - “"x'T-I « -1" _ .3 n - . ‘4'. " tr e 'L ticn r-c ha. strainet. con. q ant v, thtre s.e i 1 fff”