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Effect of past movement experiences on the reproduction of discrete movements Leveille, Serge Michel 1973

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THE EFFECT OF PAST MOVEMENT EXPERIENCES ON THE REPRODUCTION OF DISCRETE MOVEMENTS by SERGE MICHEL LEVEILLE B.Sc. (KINAN), Universite d'Ottawa, 1971 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF PHYSICAL EDUCATION in the School of Physical Education and Recreation We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1973 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t . t h e U n i v e r s i t y o f B r i t i s h C olumbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f P h y s i c a l Education and Recreation The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date June 15. 1973 i ABSTRACT The possible proactive inhibition effect of long-term past experiences upon the reproduction of discrete measurements was investigated. Ten subjects were assigned to each of the eight cells of a 2x2x2 factorial design. The two retention intervals were, 0 sec. and 30 s e c ; the two locations, 60° and 120°; the two movement lengths, 10° and 50°. Each subject received five standard-reproduction t r i a l s with an i n t e r t r i a l interval of 30 sec. The biasing effect of long-term past experiences measured by constant error, was not significant. Different target locations did not influence the intraindividual v a r i a b i l i t y of a given movement length. Significant differences were obtained between movement lengths for both constant error, in that the shorter movement was overshot to a greater extent than the longer movement; and variable error, showing a greater v a r i a b i l i t y for the longer movement. The significant increase in variable error over the retention intervals indicates that the memory trace weakened as time elapsed between the presentation of the standard and i t s reproduction. i i TABLE OF CONTENTS Page LIST OF TABLES CHAPTER I STATEMENT OF THE PROBLEM Introduction Statement of the Problem Subproblems Hypotheses Definition of Terms Delimitations Assumptions and Limitations Significance of the Study II CRITICAL REVIEW OF THE LITERATURE AND ITS RELATIONSHIP TO THE PRESENT PROBLEM Introduction 10 Adaptation Level Theory 10 Anchor Theory 15 Proactive Inhibition 17 Learning Effects 20 Cues Used in Reproduction 21 Assimilation Theory 25 Summary 26 III METHODS AND PROCEDURES Subjects 27 Apparatus 27 Organization 28 Experimental Design 28 Procedures 29 Analysis of the Data 32 IV RESULTS AND DISCUSSION Results 34 Analysis of Constant Error 34 Analysis of Variable Error 35 Test for Homogeneity 35 Discussion 37 V SUMMARY AND CONCLUSIONS 1 3 3 4 5 7 7 8 Summary Conclusions 44 45 BIBLIOGRAPHY APPENDICES A. Apparatus B. S t a t i s t i c a l A n a l y s i s C. Tables of Means iv LIST OF TABLES Table Page I The Main Effects in Constant Error 34 II The Main Effects in Variable Error 35 III Homogeneity of Error Variance in Data for CE and 36 VE Measures V ACKNOWLEDGEMENTS I wish to express my appreciation to the members of my committee, Dr. R. G. Marteniuk, Dr. R. W. Schutz, Dr. W. G. Davenport and Dr. K. D. Coutts, for their comments and collaboration throughout the preparation of this thesis making i t possible for me to complete the requirements in due time. To my chairman, Dr. Marteniuk, I wish to express special appreciation for his patience and guidance during my academic years at The University of British Columbia. CHAPTER I STATEMENT OF THE PROBLEM Introduction In learning, short-term memory (STM) has always been associated with long-term memory (LTM). Information coming from the senses i s placed in STM and i f this information i s rehearsed, i t i s then transferred into LTM. Recently, Schutz (1972) proposed that STM could also be used during retrieval tasks to f a c i l i t a t e retrieval of information. That i s , information most l i k e l y to be used i s brought back into STM where i t is more readily available. Thus, information stored in LTM could possibly interfere with incoming information stored in STM, by means of proactive interference. Williams (1971) and Stelmach (1969) have reported that proactive interference can influence motor short-term memory (MSTM). To study the possible influence of LTM on MSTM, there must be a form of movement information that i s retained in LTM. Laabs (1973) has identified such a form of information in that he found location information from a movement is kept in a central memory code. From his results i t i s possible to hypothesize that through this central memory code, LTM could affect the retention of information in MSTM. Such an effect would be mediated through what Laabs (1973) describes as an adaptation level (AL). It accounts for overshooting and under-shooting in MSTM experiments where subjects are presented with a range of 2 movements. When a subject reproduces a movement, he does so " i n reference to an average movement," which i s a combination of movements in the interpolated activity, in addition to the memory trace of the given movement. As the memory trace of a given movement decays and causes forgetting, more emphasis i s given to the AL during reproduction. This study i s an extension of Laabs' work. Since interpolated activity in a given range i s said to produce an AL in MSTM, i t i s also possible that such an AL could result from a person's long-term and daily past experiences (ALp E). Such-an ALp^ would be the mean of a l l movements (of a given limb) in the human range of movement. This mean would take into account the frequency as well as the location of the movements. Man usually works in front of himself as evidenced by writing, eating, or any precision work. The ALpg would probably be located in front of the shoulder, perpendicular to the frontal plane. To make this prediction, one must accept the assumption that reproductions are more accurate when the target location coincides with the AL. Since movements reproduced on one side of the AL are undershot, while overshot on the other, then i t i s logical that movements reproduced at the same location as the AL would have zero constant error. Then,the fact that movement reproductions are more accurate in a well-practiced range (Lloyd and Caldwell, 1965) and that reproductions are more accurate near vertical In front of the shoulder (Brown et a l . , 1948; Stelmach, 1970) would support the prediction that such an A L p E would exist at such a location. Also, as in other experiments in MSTM, this AL-,^  would become more important over retention intervals just as the AL does. 3 The AL and ALpg would not have the same influence on reproductions in time. A strength and recency trade-off would be in effect. A more recent AL would have more influence than a more distant ALpg. In other words, an AL due to interpolated activity immediately preceding repro-duction would cause most of the interference with the ALp E having l i t t l e or none. However, i f the study i s done within the context of MSTM and each subject reproduces only one length at one location, with an appropriate i n t e r t r i a l interval (ITI) to allow for sufficient trace decay, the occur-rence of an AL, due to experimental conditions, would be minimized making i t possible to investigate the presence of an AL p E. This is the framework for this study. Statement of the Problem The purpose of this study i s to investigate the possibility that an adaptation level resulting from long-term daily past experiences could influence the reproduction of a fine motor task when trace decay i s allowed to take place. Subproblems The subproblems are: 1. To study the effect of different movement lengths on intra-individual v a r i a b i l i t y while maintaining the target location constant. 4 2. To study the effect of different target locations on intra-individual v a r i a b i l i t y while maintaining the movement length constant. Hypotheses The hypotheses are: 1. An adaptation level due to past experiences causes a shift in constant error (CE) towards the ALp^. This shift is evident only in reproductions following a longer retention interval which w i l l cause a larger variable error (VE) when compared to the shorter retention interval. The shift in CE w i l l not be evident in the 0 sec. interval becuase only one movement length and location w i l l be in MSTM and the memory trace w i l l be strong enought to guide the reproduction. As the memory trace decays over time and becomes weaker, the AL^ ,^ w i l l become more influential and i t s influence w i l l be reflected in a shift in CE. The weaker memory trace used to guide reproductions after the 30 sec. retention interval w i l l be indexed by a larger VE score for that condition. 2. The VE is related to movement length in that the longer movement has a larger VE score when compared to the shorter movement. The reasoning supporting this hypothesis i s that the longer movement has a greater potential for v a r i a b i l i t y . This i s due to the fact that the longer movement is more complex and requires a longer time interval for i t s execution. Thus, the longer movement should be more variable. 5 3. The change in VE from the 0 sec. retention interval to the 30 sec. retention interval w i l l be greater for the shorter movement than for the longer movement. Laabs (1973) mentions that when discriminability of a given set of movements i s decreased, the VE can be expected to increase. In this experiment, only one movement is given but the effect of discriminability could also apply to starting and target locations. This discriminability being less for the shorter movement should result in a greater change i n VE when the memory trace i s allowed to decay when compared to the change in VE of the longer movement under the same conditions. 4. The VE for a given movement length i s not influenced by different target locations. That i s , the VE for a given movement length w i l l not vary from one target location to the other. The effect of changing location should be mediated through an AL and reflected in CE, not VE. In this experiment, location i s not a factor which causes interference resulting i n a weakening of the memory trace (because each subject i s presented only one target location). Since VE is an index of the strength of the memory trace, i t w i l l not be affected by changing the target location. Definition of terms Adaptation Level (AL). The adaptation level i s the average movement made 6 up from the combination of movements to be reproduced in the experimental situation (Laabs, 1973). Adaptation Level Due to Past Experiences (ALp E). The adaptation level due to past experience i s the average movement made up from the combination of frequency and location of a l l past movements in daily a c t i v i t i e s . Intertrial Interval (ITI). The i n t e r t r i a l interval i s the time betwwen the end of the reproduction of a standard and the start of the execution of the next standard. Memory Trace. The memory trace i s the memory state which represents the correct response and develops as a function of practicing the correct response. Movement Length. The movement length i s the distance which the subject(s) has to move in order to reach the target location. In this study, the lengths are 10° and 50° counterclockwise. Movement Location. The movement location i s the target location which the subject has to reach in order to achieve perfect reproductions. In this study, when 0° i s perpendicular to the sagittal plane, through the shoulder, the locations are 60° and 120° in a counterclockwise direction in front of the subject. When 90° is vertical to the frontal plane, in front of the right shoulder joint, the locations w i l l be 30° away from the 90° and one on each side. Thesemovement locations and the associated movement lengths are presented in diagram form in Appendix A. 7 Retention Interval. The retention interval i s any b u i l t - i n time lapse between the presentation of the standard and i t s reproduction. In this study, the retention intervals w i l l be 0 sec. and 30 sec. Trace Decay; Trace decay i s the weakening of the memory trace due to time. Delimitations The delimitations are: 1. The study i s delimited to the rec a l l of an arm movement In a counter-clockwise direction, in the horizontal plane, executed with the right arm. 2. The study i s delimited to two measurement lengths; 10° and 50°. 3. The study i s delimited to two targets locations; 60° and 120°. 4. The study i s delimited to two retention intervals; 0 sec. and 30 sec. Assumptions and Limitations The following assumptions are made: 1. Trace decay does not vary randomly but has a direct relationship with movement lengths, and retention intervals. That i s , for a given length and/or retention interval, the amount of trace decay w i l l always be the same. 8 2. Counting backward w i l l have a uniform influence on a l l movement reproductions, either length or locations, because i t i s acting through the central mechanism. 3. It is assumed that the adaptation level for past experiences i s located directly i n frong of the shoulder but an exact location i s not required for the va l i d i t y of the study. A reproduction further away from the AL w i l l be influenced to a greater extent (Laabs, 1973). For example, i f the AL__ was located at the 120° location, reproductions after the r J i 30 sec. retention interval at that location would show very l i t t l e or no biasing whereas reproductions at the 60° location after the 30 sec. delay would show a large biasing effect of the ALpE.. The investigation i s limited by: 1. The accuracy of the apparatus and of the experimenter. 2. The degree of randomness of the sample. 3. The integrity of the subjects. Significance of the Study The results of the study w i l l enable a more appropriate selection of movements, with regard to length and location, for the f i r s t few practice 9 t r i a l s when a mature individual i s being trained at a new task. It w i l l also indicate i f intraindividual v a r i a b i l i t y i s related to movement length. If such an AL p E exists, then the movements in the f i r s t few practice t r i a l s should be located further away from the AL-,,, than the desired f i n a l locations of the movement. If certain movements cause more VE than other movements, then they should be given more practice t r i a l s . (0 CHAPTER II CRITICAL REVIEW OF THE LITERATURE AND ITS RELATIONSHIP TO THE PRESENT PROBLEM Introduction When an individual makes a certain movement, there are several factors acting upon the execution of that movement. A movement is never made i n isolation but is influenced by the experiences which the individual has had prior to the movement. These forces acting subconsciously upon an individual at a given moment make up what Helson (1967) describes as an adaptation level. By eliminating immediate past experiences, which are usually present in short-term memory studies because each subject i s given several different movements, an attempt can be made to evaluate the possible effects of long-term past experiences on the execution of discrete movements. For long-term past experiences to influence the execution of movements, the AL formed would act on these movements in the form of proactive inter-ference. Several other factors, such as distance, location, movement anchoring, practice, and cues, can influence movement reproductions and their influences must be taken into consideration. Adaptation Level Theory The theory of adaptation level i s based upon the assumption that a certain order prevails over the judgements made by man (Helson, 1967). 11 Included In these judgements i s the psychophysical realm. The AL works in such a way that stimuli located at the AL seem to be neutral whereas stimuli located above or below the AL value w i l l e l i c i t positive and negative responses from the subjects. Helson maintains that this AL is not static but changes in accordance with the prevailing conditions of stimulation. The AL which becomes the frame of reference for psychophysical judgements is a function of a l l the stimuli acting upon or within an individual at the time of judgement as well as those stimuli perceived in the past. Thus, the prevailing AL would be comprised of a l l long-term and immediate past experiences as well as the given stimulus. Helson (1967) identifies three primary forces which make up the AL acting during a given experimental situation. The f i r s t one i s the experimental stimuli which are the stimuli being judged; second i s the contextual stimuli which are forming the background or standard for judgement; and third i s a residual factor which represents the effects of a l l related previous stimulations. In the present study, the experimental stimulus w i l l be the given distance at the given location. That part of the adapt-ation level made up from the contextual stimuli w i l l be the same as that made up from the experimental stimulus. It must be noted that there w i l l be only one distance at one location presented to the subject. Of special importance for this study is the residual factor which w i l l be comprised of long-term past experiences only, because the subject is presented with only one distance at one location during the experiment. Of the three types of stimuli which combine to form the adaptation level, only the f i r s t 12 and third w i l l be present in the study. Another aspect of the adaptation level theory is the importance given to the AL over time (Helson, 1967). As the time lapse from the presentation of a standard and the reproduction of that standard is increased, more importance i s given to the AL when the reproduction of the standard is made. That i s , the longer the interval between presentation and reproduction, the more the reproduction w i l l approach the value of the AL. It is assumed that when the memory trace decays and becomes weaker, i t is less able to guide reproductions, making them more susceptible to other factors such as the AL. Also implied in this theory i s the importance given to each factor in forming the prevailing AL. A strong memory trace would have the most influence i n the formation of the adaptaion level because of i t s strength and recency. As the strength of the memory trace decreases as i t decays, the contextual stimuli gain in importance and become more important in forming the AL. Although they are not as recent as the actual memory trace, the pooling of several contextual stimuli increase their strength in relation to the decaying memory trace. The last in importance are the residual factors or the long-term past experiences. If both experimental and contextual stimuli are present, then l i t t l e importance would be given to the residual factors in forming the prevailing adaptation level; this i s not the case for the present study. 13 A similar importance-recency trade-off has been reported by Levin, Craft and Norman (1971) when they tested an additive model for averaging motor movements. When their subjects had to make a movement which was the average of three or five given movements, the averaging responses could be predicted by a weighted average of the given stimuli. The influence of the last given movement was greater than the influence of the earlier movements. Thus, in AL terminology, the experimental stimuli would have more importance in forming the adaptation level than would have the contextual stimuli which in turn would have more importance than the residual factors. The problem to be examined by this study i s whether the residual factors can gain^enough importance in the absence of contextual stimuli to influence the reproduction of precise motor movements. E l l i s (1973) attempted to evaluate the adaptation level theory using sounds as the experimental stimuli and varying the intensity (loudness). In the f i r s t part of the experiment, the subjects received seventy-two t r i a l s centered at either 50, 65 or 80 decibels. Three interstimulus intervals of one, four and seven seconds were employed separating the presentation of the standard from the comparison which was equal, plus, or minus one decibel. In the second part, a l l subjects received 72 t r i a l s centered on 65 decibels. The adaptation level theory would predict that in the second part, as the interstimulus interval increases, the errors of the subjects who were given the 50 decibel sound in the f i r s t part would become more negative whereas the error of the subjects who were given the 80 decibel 14 sound would become more positive while the error of the 65 decibel group should be maintained. In accordance with the theory, a significant effect due to the prior sound level was found but the different time intervals produced a similar negative shift in errors which i s contrary to the predictions. However, i t is f e l t that these results could s t i l l be explained with reference to the adaptation level theory. On the one hand, the 72 t r i a l s of part one might not have been sufficient to create a contextual level strong enough to influence the judgement of the 72 t r i a l s of the second part, following the 5 minute rest between the parts. Furthermore, the three experimental levels of intensity might have been greater than the individual's AL for intensity before the experiment. Thus, the negative shift in error with increasing interstimulus intervals might reflect an adaptation towards the pre-experimental AL. The effect of the f i r s t 72 t r i a l s would be to slow down this adaptation to the pre-experimental level. More closely related to the present study is the investigation by Laabs (1973) who proposes a model of motor short-term memory based on the adaptation-level theory and incorporating variable and constant error. The Laabs study uses movement reproduction as opposed to E l l i s ' sound recognition, making i t more similar to the present experiment. There were 6 movement lengths ranging from 10° to 35° in 5° steps and 12 f i n a l locations which were also separated by 5° intervals. The same standard-reproduction sequence was used, with reproductions being made with a movement length different from the one used in the standard to make the 15 distance cue unreliable. In the group where the location cue was to be unreliable, the reproductions were made to different f i n a l locations. Two retention intervals were used, 0 sec. or 12 sec. with the latter being either a rest interval or f i l l e d with counting or a spatial reasoning test. The data reported in the study support entirely the adaptation level theory. As the retention interval i s increased, more emphasis i s placed on the experimental or contextual AL which results in increased under-shooting of the longer movements as opposed to increased overshooting of the short movements. Of importance for the present study i s the fact that this tendency toward the AL i s also postulated for location; that i s , movement reproductions w i l l be biased towards the AL after a retention interval. If, i n the absence of contextual stimuli, the residual factors or long term past experiences are a major influence i n the formation of the prevailing AL, then the biasing effect would be reflected in a shift of the constant error scores toward the adaptation level. Anchor Theory Another factor which can be of some help in movement reproductions i s anchors. Anchors serve as points of reference to which the movement to be reproduced can be compared and/or located. MacKinnon (1972) has shown that the effect of anchors can combine with adaptation levels to influence the recognition of l i f t e d weights. Three control groups were trained with two weights, 30 gm and 250 gm, 100 gm and 300 gm, or 150 and 350 gm, which 16 were the positive stimuli. The three experimental groups were given negative stimuli of 150 gm, 200 gm, or 250 gm in addition to the positive stimuli. Subjects learned not to respond to the negative stimuli because reinforcement followed only a correct response to the positive stimuli and was withheld when the negative stimuli were presented. In the experi-mental situation, the subjects were presented with weights ranging from 50 gm to 500 gm at 50 gm intervals and were asked to recognize the learned weights. The values of subjective equality seemed to be pushed away from the negative stimuli in the experimental group when compared to the control groups. Thus, the effect of known or learned anchors can influence the judgement of weight when kinesthesis i s used as a means of evaluation. These anchors work i n a psychological manner similar to that of adaptation levels. Caldwell and Herbert (1956) had previously shown that an anchoring effect was present in a horizontal straight arm movement originating from the shoulder joint. In their experiment, 0° was in front of the shoulder while 90° was perpendicular to the sagittal plane. They report clear evidence of perceptual anchoring at the ends of the range, 0° and 90° positions. There was only a slight evidence of increased accuracy near the midpoint of the range tested. For the present investigation, considerations were given to the possible influence of anchors on the reproduction of movements when the selection of movement lengths and locations was made. The range of movement made 17 possible through the combination of elbow flexion and shoulder rotation used in this study is much greater than that of Caldwell and Herbert (1956), covering approximately one hundred and eighty degrees in the horizontal plane. The two movement locations are approximately sixty degrees from the closer end of the range where the anchoring effect would be located and strongest. Unlike MacKinnon (1972), there are no negative stimuli used within the range to create an anchoring effect. Since a l l the movements are to be executed i n a counterclockwise direction, the movement lengths were selected so that they could be easily executed without undue stretching of muscle fibers at both locations. A movement longer than f i f t y degrees could have been easily reproduced at the 120° location but would have caused greater stretching of the musculature to reach the starting location xtfhen the target location was 60°, making the two conditions dissimilar. Proactive Inhibition Comparisons are always made between verbal short-term memory and motor short-term memory; this i s also the case for proactive inhibition (PI). In verbal STM, PI is a strong factor. On the other hand, several studies in MSTM have failed to find the effect of PI (Adams and Dijkstra, 1966; Posner and Konick, 1966). However these two studies used relatively long IT1 which might prevent PI. Schmidt and Ascoli (1970) in an attempt to resolve the problem, gave their subjects either a 10 or 90 second ITI in the reproduction of a linear movement. Their results pointed to a null 18 effect of ITI because no PI occurred in the experiment which is similar to the results of Montague and H i l l i x (1968). On the other hand, a similarity between verbal and motor STM with respect to proactive inhibition has also been reported. Stelmach (1969a) showed that absolute errors at r e c a l l were directly related to the number of prior positions. The number of prior positions varied from 0 to 4. The same researcher (Stelmach, 1969b) related PI to the similarity of responses. He found that absolute errors at r e c a l l were inversely related to the similarity of the prior responses about the target position. This result was replicated later by Craft and Hinrichs (1971). Ascoli and Schmidt (1969) used a simple linear positioning task to study the effect of PI in MSTM. The subject was presented with either 0, 2, or 4 positions before being given the criterion which he was to re c a l l 10 or 120 seconds later. A l l the movements were recalled in reverse order. PI effects were found only in the group with 4 prior positions resulting in greater absolute error and greater undershooting with algebraic r error when compared to the other two groups. In a similar study, Williams •(1971) manipulated prior positions, practice reinforcements of the criterion distance, and retention interval. Absolute error scores at r e c a l l indicated a PI effect but only for the condition of five prior learning, with one criterion distance after 15 and 50 sec. retention intervals. 19 At best, proactive inhibition seems to be relatively weak in producing interference in MSTM. This indication i s similar to that of Montague and H i l l i x (1968). They gave each subject seven t r i a l s with different lengths with each t r i a l consisting of four standard-reproduction sequences. The between t r i a l comparisons showed no effect of PI but such an effect was evident when only the f i r s t standard-reproduction sequence of each t r i a l was compared. Thus, the PI effect was not strong enough or important enough in the formation of the prevailing AL to offset the importance given to two or more repetitions of the experimental stimuli in making up this AL. The negative effect of PI with decreased ITI when each subject i s given repeated presentations of the same position could be due to the fact that with repeated presentations, the memory trace enters long term memory where i t could not interfere with information coming into short-term memory. This null PI effect from long-term memory has been proposed for verbal memory by Scott, Whimbley and Dunning (1967). Proactive inhibition seems to be the weaker factor when compared with retroactive inhibition. This was shown by Craft and Henrichs (1971) and Craft (1973) when they studied the effect of interfering movements either before the standard-reproduction sequence or interpolated between the standard and the reproduction. Although weak, the proactive inhibition effect seems to be present. In the Levin, Craft and Norman (1971) additive model for motor movements, 20 the subject when asked to average a series of given movements, subconsciously placed more emphasis on the movement presented just before, indicating a PI effect. When E l l i s (1973), in his evaluation of Helson's adaptation level theory, mentions that a significant effect due to prior levels was evident, he is in fact proposing a PI effect. Similarly, PI, as well as retroactive inhibition, has to be a factor in both Laabs' adaptation level theory for movements (1973) as well as Pepper and Herman's assimilation theory (1970). If i t wasn't for the interference factor, neither adaptation nor assimilation could result from a series of movements nor could they in turn affect the next movement. In the present study the only source of PI expected to influence reproduction i s that caused by long-term experiences prior to the testing situation. Some PI effect could be generated from t r i a l to t r i a l but the experimental procedures used attempt to minimize this effect. These w i l l be discussed in the next section of this chapter. Learning Effects The amount of learning that the subject does during the experiment is very important. If a high level of learning i s achieved, then the prevailing adaptation level would be formed primarily by the experimental stimuli with l i t t l e importance given to long-term past experiences, defeating the purpose of this experiment. In the Williams study (1971) the PI 21 effect appeared after a 15 sec. retention interval but disappeared when three practice reinforcements were given. Montague and H i l l i x (1968) report the disappearance of a PI effect after only two practice reinforce-ments. On the other hand, Adams and Dijkstra (1966) report that six reinforcements were needed to significantly influence absolute errors in reproduction. Similarly, a study by Leveille (1973) showed that in a linear task, the majority of learning took place in the f i r s t ten t r i a l s as reflected by a decrease in variable error. This was without verbal knowledge of results and zero ITI. It was also shown that twenty-five practice t r i a l s did not significantly affect constant error scores. In the present study, the subject w i l l receive only five presentations of the criterion distance in a standard - reproduction sequence. There w i l l be a thirty second ITI. The subject was told not to rehearse the previous movement during this interval in order to minimize the PI effect from t r i a l to t r i a l thus reducing the learning effect as shown by Bjork, Laberge and Legrand, 1968. The subjects i n the thirty second retention interval group w i l l have that extra time, in addition to the ITI, to allow for trace decay; again reducing the learning effect. Cues Used in Reproduction Researchers have investigated three types of cues which could subserve the kinesthetic process; location, distance and force (or tension). 22 Recently, Marteniuk and Ryan (1972) suggested that a horizontal straight arm movement was subserved by a metathetic (substitutive) process which would indicate that for the given task, judgements were made through the use of location cues rather than distance cues. Marteniuk and Roy (1973) mention, after reviewing the literature, that physiological evidence indicates the three types of kinesthetic receptors that subserve kinesthesis are found in the joint and project to the sensory cortex. These receptors would code position, direction, speed, and acceleration but not movement distance as such. These facts and the experimental data support the researchers* conclusion that distance cues, in the given task, provided less precise information about arm displacement than location cues. They further conclude that there might not be any receptors for distance making this type of information uncodeable. For distance information to be codeable, the subserving receptors would have to be located in the muscle and monitor the extent of contraction. Granit (1972) mentions the fact that the large primary afferents from the muscle spindles project to the sensorimotor cortex. Thus, this would indicate that distance information can be encoded ('assuming that effort can be equated with distance), which i s contrary to Marteniuk and Roy (1973). On the other hand, these cues, as suggested by Marteniuk and Roy (1973) would be of lesser importance than location cues. According to Granit (1973), the information from the muscle spindles i s integrated with the inflow of information from tendons and joints and i s included in a 23 mechanism for verifying the execution of movements and is not necessarily used in the guidance of the movement. Several researchers have isolated and studied location and distance cues (Posner, 1967; Keele and E l l s , 1972; Marteniuk and Roy, 1973, Laabs, 1973). The methodology i s quite simple; changing the starting location and asking the subject to reproduce the end location makes the distance cue unreliable whereas changing the starting location and telling the subject to reproduce the movement extent renders the location cues unreliable. Maintaining the same starting and target locations for reproductions allows for both cues to be available simultaneously. The fact that movement distance information decays over an empty retention interval whereas movement location decays very l i t t l e combined with the fact that inter-polated ac t i v i t i e s requiring attention cause a relatively small increase in decay of distance information but a significant decay of location infor-mation led Laabs (1973) to suggest a two mode system of storage. Location information i s rehearsable and stored in a central mode whereas distance information i s not rehearsable and stored in a kinesthetic mode. The effects of retention intervals and interpolated mental activity have been studied in relation to different movement lengths (Stelmach, 1970; Stelmach and Wilson, 1970). Longer movements decay over an empty retention interval with interpolated mental activity adding very l i t t l e to the decay. However, shorter movements suffer l i t t l e loss over an empty 24 retention interval but significant loss when mental activity i s introduced. Since short movements decay l i t t l e unless a secondary task i s introduced would indicate that such movements depend on location information which follow the same rule; similarly long movements would depend more on distance information. This deduction is contrary to Stelmach*s (1970) who maintains that short movements depend on distance cues. The effects of force have been studied by Wllberg (1969). He showed that constant pressure did not appear to have an effect upon the storage of information and i t s decay from STM. In addition to proprioceptive feed-back, Adams, Marshall and Goetz (1972) studied the effect of visual and auditory feedback. The greatest loss in retention occurred for the longer interval of 90 sec. with the least amount of feedback available. That i s , making a l l sources of feedback (auditory, visual and proprioceptive) unreliable. In a l l the experiments reported in this section, the same subject had to reproduce several movements which vary in length at several locations. That i s , confounded in the experimental results, are the possible influences of changing movement length and target location as well as the influence of the experimental treatment. Such an influence has been proposed by Brown (1948) Lloyd and Caldwell (1965) and Stelmach (1970) who have indicated that accuracy in reproductions might vary with the amount of practice and the target location. These two factors of movement length and movement 25 location are especially confounded in experiments where distance or location cues are made unreliable. A reproduction using either a different movement length or a different target location, depending on the situation, i s compared to the standard, which means that the effect of the experimental manipulation i s not tested under the same conditions. Then the variations in reproductions obtained could result from the experimental treatment or the procedures used or both. This experiment i s designed to investigate the possible effects of changing the distance or location for the reproduction of a standard. Assimilation Theory For MSTM, Pepper and Herman (1970) have proposed an assimilation theory. In their model, a single memory trace either interacts with interfering movements and/or decays over time. When the memory trace of a short movement interacts with that of a long movement, the resulting memory trace i s a combination of both traces along the extent dimension. At rec a l l the short movement w i l l be overshot whereas the long one w i l l be undershot. When the memory trace i s allowed to decay, i t does so along the extent dimension resulting in a shorter movement at r e c a l l . Interpolated mental activity i s said to cause a positive shift in CE at reproduction. It must be remembered that the AL theory of MSTM presented by Laabs (1973) makes the same predictions as the assimilation theory and is more closely related to the present investigation. 26 Summary It has been shown that an adaptation level can be set up by the combination of several movements in STM and that such an adaptation level could Influence movement reproduction through proactive inhibition. The experiment i s designed to investigate the possibility that a similar AL could be set up from long-term past experiences stored in LTM and influence movement reproductions in a similar manner. The experimental design w i l l permit an evaluation of the effect of changing movement length and target locations for the reproduction of criterion movements. Comparison of the results of the present experiment with those of experiments exposing the subject to a range of movement lengths and location w i l l also permit an evaluation of the effect of such a range on accuracy and va r i a b i l i t y of movements. Zl CHAPTER III METHODS AND PROCEDURES Subjects Eighty right-handed male subjects participated in the experiment. Fifty-six of these subjects were from undergraduate and graduate studies at The University of British Columbia. The remaining twenty-four were either involved in training or members of the Vancouver Y.M.C.A. The subjects were assigned to each of the eight groups in a systematic, unbiased fashion making a total of ten subjects per group. The age of the subjects ranged from 18 to 47, giving a mean of 23.4 years. The group means ranged from 20 to 27 years. Apparatus The movement apparatus utilized for the experiment i s the same as that used by Marteniuk and Roy (1973). A pict o r i a l description of the apparatus i s shown in Appendix A. The apparatus consisted of a half-circle of masonite board which had a diameter of 5.0 feet. On the board an arc and half degree calibrations were drawn. A lever was attached to a near frictionless pivot at the midpoint of the chord describing the arc. On the lever arm, one foot away from the centre of the pivot, there was a 5.5 inch handle which was used to move the lever. A pointer extended from the lever arm to the circumference where vertical indicators projected 28 downward making i t easier to read the performance score. The subject moved the lever in the horizontal plane in a counterclockwise direction. Wooden blocks were used to indicate the starting and target locations. The frictionless pivot was fastened to a table. The base of the handle on the lever arm was approximately 45 inches from the floor, 7 inches higher than the table top. Organization The same experimenter tested a l l the subjects at the rate of approx-imately ten minutes per subject for a total of approximately twenty testing hours. The majority of the subjects were tested in The University of British Columbia Motor Learning Laboratory. The other subjects were tested at the Vancouver Y.M.C.A. The same apparatus was used at both testing locations and environmental factors such as noise level, a ir temperature, and size of testing room were almost identical. Experimental Design The subjects were divided into eight groups. Each group was given only one experimental treatment. There was one group for each of the movement lengths (10°, 50°), at each of the two locations (60°, 120°), and for each of the two retention intervals (0 s e c , 30 s e c ) . Thus, a subject received five t r i a l s for a given length at a given location for a 29 given retention interval. These lengths and locations were selected to minimize the possible effect of "anchors" as discussed in Chapter II. The design used was a 2x2x2x5 (retention interval x movement location x movement length x tri a l s ) factorial design with repeated measures on the last factor. A diagram ill u s t r a t i n g the different movement locations and movement lengths i s included in Appendix A. As can be seen, each location (60° and 120°) i s the movement location for two movement lengths (10° and 50°). In addition, each movement length at each location w i l l have two groups; one for the 0 sec. retention interval and one for the 30 sec. retention interval. Procedures The subjects were not allowed to see the experimental apparatus to minimize the visualization of the task before the actual testing. They were asked to strip from the waist up to prevent extraneous cues from the stretching of their clothing around the shoulder and elbow joints and along the arm. The subjects were blindfolded and given ear mufflers before entering the testing area. The subject was guided to a standard position in front of the apparatus by the experimenter. The apparatus came approximately to a height half-way between the standing subject's shoulder and hip. The subject stood as close as possible to the table without touching i t with his frontal plane parallel to the table. The subject's right shoulder was directly in line and perpendicular to the pivot. The subject was instructed to remain in this 30 position for the duration of the experiment. Once in the standard position, the subject's right hand was placed on the handle. He was told to move the lever to get accustomed to the easiness of movements made possible by the near frictionless pivot. After a few seconds, he was told to bring both arms down to his side. To move the lever in the horizontal plane, a combination of elbow flexion and shoulder rotation i s required. The subject was instructed to maintain his movement as consistent as possible throughout the experiment. It was pointed out that time in movement was not a factor and that the movement should be of a comfortable and uniform velocity. On the command "ready" the subject was told to move his hand from his side to the handle of the lever which was at the starting position. Verbal directions were given by the experimenter to f a c i l i t a t e finding the handle. The command "move" told the subject that he was to move the lever at a constant speed in a counterclockwise direction u n t i l hitting a block. The subject remained at the block for two seconds, then released the handle and brought his hand back to his side. This was the beginning of the retention interval during which the experimenter returned the lever to the starting position. After the retention interval, the experimenter gave the command "ready" which signaled the subject to regrasp the lever. On the command "reproduce", the subject tried to reproduce the standard, which he had been given before, as accurately as possible. When the subject f e l t he was accurate, he released the handle 31 and brought his hand back to his side. This was the start of the inter-t r i a l interval. The subject was given five such pairs of movements to make up the five t r i a l s required for the experiment. The retention intervals used in the experiment were zero and thirty seconds. In the 0 sec. retention interval, the experimenter returned the lever to the starting position while the subject returned his hand to his side, as soon as this was executed, the experimenter gave the command "ready" followed by "reproduce". The subjects in the 30 sec. retention interval groups were given a three digit number as soon as they released the lever after the standard movement. They were instructed to count backward from the given digit by three's, out loud and as fast as possible. After 30 seconds of counting, the experimenter gave the command "ready" followed by "reproduce" when the subject had regrasped the handle. The thirty second retention Interval was chosen because i t was f e l t that this time lapse would allow sufficient decay of the standard to allow the ALpg a sufficient gain in importance so that i t s effect could be noticed in the reproductions. Some studies in STM have used longer retention intervals of 120 sec. (Ascoli and Schmidt, 1969); and 90 sec. (Marshall, 1972) but other researchers have had significant results using retention intervals of 30 s e c , (Stelmach and Barker, 1970) 20 s e c (Stelmach and Bassin, 1971, Stelmach and Wilson, 1970), 15 sec. (Williams, 1971) and 12 sec. (Laabs, 1973). 32 The mental task was introduced to prevent the rehearsal of location information. Laabs (1973) has shown that location information decays very l i t t l e over a rest period unless rehearsal is prevented. In this study, the ava i l a b i l i t y of both distance and location cues at reproduction, made i t necessary to introduce this mental activity to promote trace decay. During the 30 sec. ITI, the subject was asked not to rehearse the previous movement in order to allow for i t to decay in STM; Bjork, LaBerge and Legrand (1968) found that instructions to forget a prior item reduced the proactive inhibition effect, hence the learning capacity. Here again, the thirty second delay was judged sufficient for sufficient trace decay thus limiting the amount of learning from t r i a l to t r i a l . Analysis of the Data The two dependent variables were constant error (CE) and variable error (VE). CE i s defined as the mean algebraic error for each subject, while VE is the standard deviation of each subject's algebraic error scores about his CE. These measures have been shown to be s t a t i s t i c a l l y independent (Schutz and Roy, 1973). Pepper and Herman (1970) suggested that CE measured the biasing effect of the experimental treatment on the memory trace. Laabs (1973) contends that VE measures the strength of the memory trace; the smaller the VE, the 33 greater the strength of the memory trace. In the present study, CE i s postulated to measure the biasing effect of the AL_„ whereas VE i s r f c i thought to measure the strength of the memory trace. The CE was calculated as the mean of the S's five t r i a l s . These CE means were analyzed in a 2x2x2 (retention interval x movement length x movement location) analysis of variance. The VE, or the standard deviation, for each S's five t r i a l s , was determined. These VE scores were analyzed in a 2x2x2 (retention interval x movement length x movement location) analysis of variance. 39 CHAPTER IV RESULTS AND DISCUSSION Results Analysis of Constant Error The analysis of variance of CE (Table 1, Appendix B) revealed a significant main effect for distance F (1, 72) = 6.61, p<.05. The other two main effects of retention interval F (1, 72) = 1.33, and location F (1, 72) = 0.04 did not reach significance nor did any of the interactions. Thus the only significant difference in CE was between the two movement lengths of 10° and 50°. The CE values for these main effects are represented in Table 1. Table I The Main Effects in Constant Error Main Effect (degrees) Retention Distance* Location 0 sec. 30 sec. 10° 50° 60° 120° 1.5 2.5 3.1 0.9 1.9 2.1 * Effect significant, p<.05 35 Analysis of Variable Error The analysis of variance of VE (Table II, Appendix B) revealed a significant main effect of retention interval F (1,72) = 23.14, p<.01 and distance F (1, 72) = 27.19, p<.01. The other main effect of location F (1, 72) = 2.93 did not reach significance nor did any of the interactions. Thus, there was a significant difference in VE between the two retention intervals of 0 sec. and 30 sec. Similarly, the VE for the short movement of 10° was significantly different from the VE for the long movement of 50°. The VE scores for these main effects are represented in Table II TABLE II The Main Effects i n Variable Error Main Effect Degrees Retention ** Distance ** Location 0 sec. 30 sec. 10° 50° 60° 120° 2.6, 4.5 2.5 4.6 3.9 3.2 ** Effect significant; p<.01 Test for Homogeneity A test for homogeneity of variance was applied to the data. Since only the main effects in CE and VE were significant (Table I and Table II), 36 i t was decided to apply Hartley's test (Winer, 1962: 92-96) only to those groups, giving two treatment groups with forty subjects per group. The results of the test are summarized in Table III. As evident in Table III there i s a borderline case of heterogeneity in error variance of both dependent measures CE and and VE at the .01 le v e l . Even though that i s the case, i t i s f e l t that the significant effects obtained are s t i l l valid because the analysis of variance would be f a i r l y robust to deviations from homogeneity of error variance due to the equally large number of subjects (40) per group (Edwards, 1960: 132). Table III Homogeneity of Error Variance in Data for CE and VE Measures Dependent Variable Group Variance Fmax - D l 7.4 -CE —• ' D 2  18.0 2.4 2.4 2.6 Fmax (2, 39) = 1.96 p<.05 Fmax (2, 39) - 2.44 p<.01 37 Also to be taken into consideration is the level of significance reached by the different main effects. The main effect of distance in CE reached a value of F (1, 72) = 6.61 which is much closer to the F (1, 72) = 7.01 value which i s required for significance at the .01 level than the F (1, 72) = 3.98 value which is required for significance at the .05 level. Here again, this significance i s probably valid because of the strength given to the analysis of variance by the large and equal number of subjects per group. Similarly, the F value obtained on VE scores for the main effects of retention interval F (1, 72) = 23.14 and distance F (1, 72) = 27.19 are highly significant at the .01 level which requires an F value of only F (1, 72) = 7.01. Thus, i t is f e l t that these significant differences are valid. Discussion Since no significant differences were obtained in the CE measure for retention intervals and locations, the f i r s t hypothesis must be rejected. That i s , long-term past experiences do not affect the reproduction of discrete movements. To ensure that the possible effect of long-term past experiences had not been influenced by a practice effect of the five t r i a l s , the scores for CE of the f i r s t t r i a l of each subject were entered in an analysis of variance. As shown in Table III, Appendix B, none of the main effects or interactions reached significance. This being a second proof that past 38 experiences in LTM do not affect movement reproductions. The null effects show that either no ALp_; is formed in LTM or there i s no PI from LTM or both of these. On the other hand, an AL for LTM acting through PI might not be strong enough to influence reproductions. It seems that the f i r s t two suggestions are l i k e l y to be occurring. If one accepts Hebb's physiological point of view (Hebb, 1961:41) that on unstable activity trace becomes a more stable structural trace with reinforcement, without getting involved in arguments concerning a single mechanism memory theory (Gruneberg, 1964, 1970) or a dual mechanism memory theory (Scott, Whimbley and Dunning, 1967a, 1967b), then i t i s possible that after sufficient reinforcements the resulting structural trace is an entity in LTM and as such is treated individually during retrieval. Thus, a l l traces in LTM would be kept separate, although probably in some hierarchial way, and would not combine to form an AL for LTM. Scott, Whimbley and Dunning (1967a, 1967b) have shown that in verbal memory, there is no PI effect from previously learned items in LTM acting upon newly learned items in STM. This lack of PI could be explained for motor memory using the model for MSTM developed by Craft (1973). His results indicate that the interfering effect of one movement on the recall of another occurs at the time of completion of the second movement rather than at r e c a l l . Furthermore, the degree of interference is related to the amount of time elapsed between establishment of the memory trace and the trace 39 which interferes with i t . According to this model, the effect of PI is represented i n this form; I - At - S - R where I is the interfering trace, At i s the time elapsed between the interfering trace (I) and the stimulus (S). R i s the reproduction of S. In the present study, I is located in LTM but i s not actively reproduced in the experimental situation. The time elapsed between I and S (At) i s indefinite but greater than any time interval used in studies of STM. Thus, only the remaining two factors S and R are physically present. Because of the very weak or non-existent I and the relatively long At, PI in the present study could not influence the reproduction of the stimulus. Of interest, concerning constant errors, i s the lack of significant change over retention intervals for either of the distances at either location. This i s i n contrast to the study by Laabs (1973) and other similar studies (Stelmach, 1970; Stelmach and Wilson, 1970) which, after a retention interval, report increasing undershooting for long movements and increasing overshooting for short movements. Perhaps those biases toward an AL can only be seen in studies where the same subject is given different movement lengths at different locations thus setting up what could be called an experimental AL. Therefore Laabs' (1973) prediction that forgetting in the central mode of storage w i l l cause a biasing effect toward the location AL, could only be applied to experiments where a subject i s presented with a range of distances and locations. The same restriction could be applied to the prediction that forgetting in the kinesthetic mode of a storage w i l l cause a biasing effect toward the movement length AL although the 40 significant effect of distance on CE found in the present study might indicate the presence of an inherent adaptation level for movement length. Since the longer distance was only slightly overshot, this AL would be represented by a movement slightly longer than 50°. Hirschfield, Leveille and Thomas (1973), also using independent groups, did not find such a trend in CE for linear movements of 6 cm., 12 cm., 18 cm., 24 cm. and 30 cm. Unlike the present study, the movements were reproduced at different locations to the l e f t of the right shoulder, which could be moving away from the location of greatest accuracy, apparently located at 90° in front of the shoulder. More research i s needed in this area but Brown, Knauft and Rosenbaum (1948) and Stelmach (1970) hint to i t s existence. In the present study, the two locations were symmetrical about the 90° which could explain why the CE were similarly inaccurate. Another point of interest concerning constant error i s the positive shift over retention interval. These findings were not significant but are i n agreement with Pepper and Herman (1970) who postulate such a shift when the retention interval i s f i l l e d with a mental activity such as counting. A quick look at the R x D interaction reveals that both distances have a similar shift in CE. The 10° distance went from 2.6 to 3.5; the 50° distance, from 0.4 to 1.4. Thus, i t seems that the assumption concerning the effect of counting on different movement lengths was valid although this cannot be given unequivocal status because the experiment was not designed to look at this problem. It i s possible that shorter movements decay less 41 and are influenced to a lesser degree by counting whereas longer movements could decay more but at the same time be more susceptible to counting; such a combination would yield results similar to those obtained. Such an interaction could be possible since the VE scores did di f f e r in the predicted direction for movement lengths with VE here being interpreted as an index of the strength of the memory trace. The f i r s t hypothesis also suggested that intra-individual v a r i a b i l i t y would increase following a retention interval. The main effect of retention interval for VE was highly significant. This result i s similar to Laabs (1973) and i s seen to undermine the assimilation theory of Pepper and Herman (1970) which requires that the subject reproduce f a i t h f u l l y the extent represented by the decaying trace yielding a negative shift in CE. However, i t has been shown that the vari a b i l i t y increases when the memory trace decays. The second hypothesis which related VE directly to movement length was supported. The main effect of distance was significant for the VE scores with the shorter movement being less variable than the longer one. This result is similar to those of Hirschfield, Leveille and Thomas (1973) who found that VE scores increased as the movement length increased. This finding could be important, unless steps are taken to balance the effect, in studies which have different movement lengths for the standards and reproductions. When the reproduction length is shorter, the subject reproduces with a movement which i s less variable and could conceivably be less affected by manipulations. However, a longer movement in reproduction 42 is more variable than that of the standard and could be influenced to a greater degree by biasing factors. Unfortunately, studies attempting to look at the different cues subserving kinesthesis have confounded this effect. To make the distance cue unreliable, different movement lengths are used to reach the same location; the present study has shown that different movement lengths have different VE. The third hypothesis predicted a significant interaction between movement lengths and retention intervals. The greater increase in VE for the shorter movement when compared to the VE increase of the longer movement did not materialize. In fact both movement lengths changed in a similar manner. Thus, when different movement lengths are subjected to the same conditions, their changes are similar. It seems that discrimin-a b i l i t y of starting and target locations is not an important factor. The predictions of the fourth hypothesis, that changing the target location for a given movement length, would not influence the va r i a b i l i t y of that movement, was correct. The main effect of location as well as the interactions of location and distance and location and retention interval did not reach significance. Thus, in independent groups, changing the target location of a given movement does not affect that movement's var i a b i l i t y . In studies attempting to investigate the location cues, the same movement length i s used, hence having the same va r i a b i l i t y , but the reproduction might be affected by PI since the same subject experiences 43 both locations. Marteniuk and Roy (1973) have reported such bias. CHAPTER V SUMMARY AND CONCLUSIONS Summary The main purpose of this study was to investigate the possibility that an adaptation level made up of long-term past experiences could influence the reproduction of discrete movements. Interference from the experimental situation was kept to a minimum allowing such an AL to possibly influence movement reproduction. Other problems investigated were (1) the evaluation of VE for different movement lengths at the same location and (2) the differences of VE for a given movement length at different locations. Eighty right-handed male subjects were tested. Ten subjects were assigned to each group. The task involved the reproduction of a given standard after a given retention interval at a given location. One group was assigned to each of the cells of a 2x2x2 factorial design. The two retention intervals were 0 sec. and 30 s e c ; the two movement locations, 60° and 120°; and the two movement lengths, 10° and 50°. Each subject was given five standard-reproduction sequences of the given standard for the given retention interval at the given location with an ITI of 30 s e c 45 The results indicated that long-term past experiences did not influence movement reproduction and that the target location did not affect the var i a b i l i t y of a given movement. A significant difference in va r i a b i l i t y between the two movement lengths was evident, as well as between the two retention intervals. Conclusions The conclusions were: 1. Long-term past experiences do not influence the reproduction of discrete motor movements. 2. Changing the target location for a given movement length does not change the v a r i a b i l i t y of that movement. 3. The vari a b i l i t y of a movement is related to the movement length. In this experiment, the longer movement was significantly more variable than the shorter movement. 4. 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New York: McGraw-Hill Book Co., 1962. 49 APPENDIX A Apparatus MOVEMENT APPARATUS ILLUSTRATION OF MOVEMENT LENGTHS AND LOCATIONS 52 APPENDIX B S t a t i s t i c a l Analysis 53 Analysis TABLE of Variance I of Constant Error Source of Variance df M S F Retention 1 17.9 1.3 Location 1 0.5 0.0 Distance 1 88.8 6.6 * RxL 1 0.5 0.1 RxD 1 0.6 0. LxD 1 19.3 1.4 RxLxD 1 10.8 0.8 SwRxLxD 72 13.4. * P<.05 54 Analysis of TABLE Variance II of Variable Error Source of Variance df M S F Retention 1 72.5 23.1 Location 1 9.2 2.9 Distance 1 85.2, 27.2 RxL 1 3.4 1.1 RxD 1 2.4 0.8 LxD 1 0.1 0.0 RxLxD 1 0.4 0.1 SwRxLxD 72 3.1 ** p<.01 55 TABLE I I I A n a l y s i s of Variance of Constant E r r o r f o r the F i r s t T r i a l Source of Variance df M S F R e t e n t i o n . 1 124.3 2.0 L o c a t i o n 1 1.4 0.0 Distan c e 1 102.4 1.6 RxL 1 7.9 0.1 RxD 1 0.6 0.0 LxD 1 94.8 1.5 RxLxD 1 9.6 0.2 Sw(RxLxD) 72 62.7 F ( 1 , 72) = 3.98 p .05 56 APPENDIX C Table of Means 57 TABLE I The Effect of Retention Interval, Location, and Distance on Movement Reproduction in Terms of CE Retention Location Distance Error (deg) 0 sec. 30 sec. 58 TABLE II The Effect of Retention Interval, Location, and Distance on Movement Reproduction in Terms of VE Retention Location Distance SD (deg) 0 sec. 30 sec. 

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