ADAPTED PHYSICAL ACTIVITY QUARTERLY, 1994,11,179-189 O 1994 Human Kinetics Publishers, Inc.

Impairment of Visual Memory in Children Who Are Clumsy

Catherine Dwyer and Beryl E. McKenzie La Trobe University

In order to evaluate the contribution of visual memory to problems in the development of motor coordination, 9- to 13-year-old boys who were clumsy were tested on a graphic reproduction task under two delay conditions. Their performances were compared with those of control children. Individual geometric patterns were presented as a whole or sequentially, and children reproduced these pattems immediately after the inspection period or after a delay of 15 s. There was no difference in the accuracy of the reproductions of the two groups on immediate recall. After the 15-s delay, the reproductions of children who were clumsy were markedly less accurate, whereas those of the control children were unchanged. Although children who were clumsy completed their reproductions more quickly, there was no conelation between their accuracy scores and response duration. It was concluded that a difference in visual rehearsal strategies may distinguish children who are clumsy from their peers.

As noted elsewhere in this volume (e.g., Rosblad & Von Hofsten; Mon-Williams, Pascal, & Wann), skilled motor behavior is the outcome of an intricate interaction between perceptual and motor processes. In order to organize goal-directed movements, relevant information must be gathered by the perceptual systems before actions can be initiated. It is, therefore, not surprising that various deficits in the functioning of the perceptual systems of children who are clumsy have been investigated. Hulme and colleagues (Hulme, Biggerstaff, Moran, & McKinlay, 1982; Lord & Hulme, 1987, 1988a, 1988b) have proposed that visual perceptual deficits play a key role; Laszlo and colleagues (Bairstow & Laszlo, 1981; Laszlo & Bairstow, 1985; Laszlo, Bairstow, Bartrip, & Rolfe, 1988) have emphasized deficits in kinesthetic perception; and Hoare (this volume) argues that both kinds of perceptual deficits may co-occur in the same children.

In contrast to these authors, who consider deficits within perceptual modalities, Newnham and McKenzie (in press) suggested that difficulty in transferring information between modalities may characterize children who are clumsy. In a study concerned with crossmodal transfer of shape information, children who were clumsy had difficulty when the standard shape was presented visually and they were required to recognize that shape haptically. In both visual and haptic presentation, a representation of shape had to be constructed by integration of spatio-temporal information; in the former, children saw an outline shape traced out by a luminous point of light, and in the latter,

Catherine Dwyer and Beryl E. McKenzie are with the Department of Psychology, La Trobe University, Bundoora, Victoria, Australia 3083. Direct correspondence to Beryl E. McKenzie.

180 Dwyer and McKenzie

they felt the shape by manual exploration. Even when performance on both within- modality conditions was taken into account, children who were clumsy were less accurate and faster in the visual-to-haptic condition than control children. They were, however, equally capable in the haptic-to-visual condition. On the basis of these results, Newnham and McKenzie suggested that the representation of visual shape may fade more rapidly in children who are clumsy.

Findings from several other studies support this suggestion. Dewey (1991), for example, examined children's ability to produce motor sequences when imitating the actions of a model and found children with motor problems to be inferior to controls. She interpreted this finding as evidence of poor memory for sequences in the group of children who were clumsy. In another study also concerned with motor sequencing, short-term recall of visual information with and without motor output was compared (Murphy & Gliner, 1988). The sequences remembered by children who were clumsy were-less accurate than those of control children regardless of the extent of motor involvement in the response.

The aim of the experiment reported here was twofold. Our first objective was to determine whether children who are clumsy exhibit a deficit in visual memory when required to reproduce geometric patterns from memory. For this purpose, children made graphic reproductions of visually presented geometric patterns both immediately and aft& a delay. The delay placed a beater demand on visual memory and was therefore expected to affect children who were clumsy more than control children. Since earlier research had shown that children who were clumsy had greater difficulty in exercising the fine motor skills involved in drawing (Laszlo & Broderick, 1985; Lord & Hulme, 1988b), performance when copying similar geometric patterns was used as a covariate to control for possible group differences in motor skill.

Our second objective was to determine whether the differences noted by Newnham and McKenzie (in for point light presentation would also be obtained when an extended retinal image of the whole pattern was available. For this purpose, the patterns to be reproduced were presented as a whole (hereafter called simultaneous presentation) and sequentially. In the latter a narrow vertical aperture was moved over a stationary pattern so that a complete representation of the whole pattern had to be constructed by integration of the slices of pattern information that became progressively visible through the aperture (Girgus, Gellman, & Hochberg, 1980).

Method

Subject Selection

The final samples consisted of 19 boys who were clumsy and 19 who were not, age 9 to 13 years, selected from two independent schools. The intake in both schools was primarily from middle to upper socioeconomic families. Since one school enrolled only boys and the other included a small number of girls, we decided to restrict the subject pool to boys only. The selection procedure was as follows.

As a first step, class teachers and physical education teachers of grades 4 to 7 were asked to nominate children whom they judged to be clumsy. Teachers were told to select children who were thought to exhibit problems with gross and fine motor coordination. A total of 46 nominations resulted. As a second step, the Standard Progres- sive Matrices (SPM) test was administered to all children in each of the four grades, and for each child who was clumsy two or three children were matched on age, grade, and SPM score. The SPM was chosen for several reasons: It correlates highly with other

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Dwyer and McKenzie

Figure 1 - The geometric 18 patterns used on copying

and reproduction trials. The number below each figure is the total number of lines and intersections in that figure.

Procedure

Children were tested individually in a classroom at their school. Each child completed 20 test trials of which the first 4 were copying trials and the remainder were reproduction trials. On copying trials, the complete geometric pattern remained in sight while the child reproduced it. The purpose of these trials was to allow assessment of the time it took the child to complete the copy and its accuracy in the absence of a memory load. Children then completed 16 reproduction trials, half involving simultaneous presentation of the stimulus pattem and half involving sequential presentation. Trials were blocked

' according to mode of presentation, and the sequence of blocks was counterbalanced over subjects. Within each block, half of the patterns were reproduced immediately (0- s delay) and half after a 15-s delay. The order of delay trials was counterbalanced within each mode of presentation. Thus, there were eight possible sequences, and children were randomly allocated to one of these.

The particular stimulus pattern involved in each of the copying and reproduction trials was varied over subjects such that each pattern served in each order within each experimental condition an equal number of times. For half the children in each group

Impairment of Visual Memory

Figure 2 -The aperture screen used in sequential presentation of stimulus patterns. The dimensions are given in millimeters.

the visual recognition trials preceded the copying and reproduction trials; for the other half, they followed them. Total testing time was approximately 20 min, and throughout testing the experimenter was unaware of the child's group membership.

Training Trials. The child was seated at a table facing the front of the aperture screen with the experimenter on the opposite side. A set of response sheets and a pencil were provided. As soon as the child appeared at ease, a training phase of three trials was begun. The training pattern was held upright on the table in front of thechild, who was instructed to copy it as accurately as possible. Children were told that their drawing must be exactly the same as the pattern--of the same size and orientation, and with no bits added or subtracted. After completing a first copy, they were then asked to make another as quickly as possible. On the final training trial they were asked to make "the best copy you can in the fastest possible time." The purpose of training was to emphasize both speed and accuracy. Children were instructed to complete all their drawings (both copies and reproductions) in the same fashion, starting when the experimenter said "go" and saying "stop" as soon as they had completed their drawing.

Copying Trials. Each child then completed four copying trials. The stimulus card for each trial was held upright in front of the aperture screen in full view while the child copied it. No time limit was imposed, and the time taken to complete each copy was recorded.

Reproduction Trials. These followed immediately after the copying trials in the order appropriate for each subject.

Simultaneous Presentation of the Stimulus Pattern. On each of the eight trials the appropriate stimulus card was held upright in front of the aperture screen for 2 s. The card was then removed. On four of the trials, children began reproducing the pattern immediately; on the remainder, the beginning of reproduction was delayed for 15 s. Throughout the delay, children repeated the word the aloud until the experimenter instructed them to begin drawing. The purpose of this articulation was to inhibit verbal rehearsal of the characteristics of the patterns during the delay.

Sequential Presentation of the Stimulus Pattern. On each of eight trials the appropriate stimulus card was placed in the screen and the aperture was moved from left to right across the width of the stimulus card and then from right to left. The excursion in each direction took 1 s. On four trials, children began drawing immediately

184 Dwyer and McKenzie

after the second excursion was completed. On the remaining trials, reproduction was delayed for 15 s, during which time children repeated the word the aloud until the experimenter instructed them to begin drawing.

Scoring

Each of the drawings, both copies and reproductions, was scored without awareness of the subject's group membership. A drawing score was derived from three measures: a component scale, a proportion scale, and an accuracy scale. These scales will be described, and then an example of application of the scoring procedure will be provided.

Component Scale (maximum of 5 points). A component was defmed as any free- standing shape, line, or lines enclosing a space. For example, = 1 component, L = 2 components, \ = 1 component. Two subscales, number and shape, were involved, and each was allotted a maximum score of 2.5 points. The number subscale concerned the number of components within the pattern without regard for their shape.

Children received full points if the number of components in the drawing matched the number of components in the pattern. Half a point was deducted for each component not included and for each added component. The shape subscale concerned the shape of components within the pattern without regard for their number. Children received full points if the shape of the components in their drawing matched the shape of the components in the stimulus pattern, regardless of number. Half a point was deducted for each component of incorrect shape.

Proportion Scale (maximum of 5 points). Two aspects were scored. The first, with a maximum score of 1, concerned the size of the drawing. The height and width of the drawing were compared with those of the stimulus pattern. Half a point was deducted if the drawing differed from the pattern in either dimension by more than 10 mm and less than 20 mm. A score of 0 was given for those drawings that differed from the original in either dimension by 20 mm or more. A maximum of 4 points was allowed for the second aspect concerning spatial relationships between components. For each pair of components drawn in the correct spatial relationship, 1 point was given. Half a point was deducted if the orientation of reproduced components deviated from the original by 15" or more. A similar penalty applied if components were translated in any way, and no points were awarded if only one component was reproduced.

Accuracy Scale (maximum of 5 points). This scale was based on the number of lines and intersections in each figure. Where the outline shape was square, the exterior counted as 4 points and internal individual lines and intersections were counted. The possible number of points for this measure is given beneath each pattern in Figure 1. Each correct line and intersection included in the drawing was awarded 1 point. These scores were then standardized to give a score out of 5.

A possible reproduction of one pattern (see Figure 1: row 2, column 1) is given in Figure 3 for the purpose of illustrating the scoring procedure. This reproduction would receive a component score of 4.5; half a point would be deducted from the number subscale, while full marks would be given for the shape subscale. A total proportion score of 4 would be given; a full mark would be awarded for the size subscale and one point would be deducted for the second aspect concerning spatial relationships between components. Half a mark would be deducted since one element is transposed from one side of the figure to the other, and a further half mark would be deducted since the drawing is rotated by more than 15". An accuracy score of 5 would result after 4 marks

Impairment of Visual Memory

Figure 3 -A hypothetical reproduction of a geometric pat- tern; scoring is described in the text. (Note that the reproduc- tion is of a different scale than the patterns in Figure 1.)

were deducted for the exclusion of the central rectangle. When standardized this would yield an accuracy score of 2.8.

The final drawing score for each figure was the mean of the three measures and thus could range from 0 to 5. The accuracy score of 64 randomly selected drawings was rescored by one experimenter after a 6-week interval. This yielded a correlation of .92 between the standardized scores on the two occasions. Although scoring was complex, its reliability was judged to be adequate.

Results Copying Trials

Contrary to expectation, the groups differed neither in drawing score nor time taken to complete the copies, ts(36) < 1. The mean (SD) drawing scores for the controls and the children who were clumsy were 4.38 (.27) and 4.40 (.31), respectively, and the corresponding values for response time were 24.88 s (8.08) and 28.25 s (12.77). When there was no need to hold pattern information in memory the groups performed at similar levels. Given that the maximum score was 5, it is evident that the fidelity of the copies was high. The training that preceded copying may have been responsible for the unexpectedly high scores in the group of children who were clumsy.

Drawing Scores on Reproduction Trials

The means and SDs of the drawing scores for each group in each experimental condition are given in Table 2. ANOVA with Group (control, clumsy) as a between subject factor, and Mode of Stimulus Presentation (simultaneous, sequential) and Delay (0, 15 s) as within subject factors revealed significant main effects for Group, F ( l , 36) = 7 . 1 8 , ~ < .05, Mode of Presentation, F( l , 36) = 26.35, p < .001, and Delay, F ( l , 36) = 4.54, p < .05. Overall, control children had higher drawing scores than did children who were clumsy. After ANCOVA', with drawing scores on the copying trials used as a covariate, this group difference remained. However, the effect was qualified by a significant interaction with delay, F( l , 36) = 7.82, p < .01. Analyses of simple main effects showed that only the performance of the children who were clumsy declined after the 15-s delay, F ( l , 36) = 12.13, p < .001, and only the 15-s delay condition distinguished between the groups, F(1, 71) = 15.71, p < .001.

Regardless of whether recall was delayed, all children were adversely affected by sequential viewing of the patterns, the children who were clumsy no more so than controls.

'Since this was a repeated measures design and measurement of the covariate was taken only once, any adjustment in covariance analysis affects only the between group result.

186 Dwyer and McKenzie

Table 2 Mean Drawing Scores for Each Group in Each Experimental Condition

Simultaneous presentation Group Delay 0 Delay 15

Sequential presentation Delay 0 Delay 15

Control M 3.31 3.32 SD 0.43 0.46

Clumsy M 3.28 2.81 SD 0.38 0.56

Table 3 Mean Response Times for Each Group in Each Experimental Condition

Simultaneous presentation Group Delay 0 Delay 15

Sequential presentation Delay 0 Delay 15

Control M 16.02 17.68 SD 6.27 6.06

Clumsy M 13.72 16.09 SD 3.99 6.20

Response Times on Reproduction Trials The means and SDs of the response times for the groups in each condition are given in Table 3. ANOVA showed only a significant main effect of delay, F(l, 36) = 10.03, p < .001, with children taking longer to complete their drawings after the 15-s than the 0-s delay. After ANCOVA, with time to complete the copy as a covariate, there was a significant group difference that was not evident in the preceding analysis, F(l , 35) = 5.17, p < .05, with control children taking significantly longer than the children who were clumsy. Although children who were clumsy completed their drawings more quickly, there was no relation between the time they took to reproduce the pattern and its fidelity, r = .02 for the children who were clumsy and r = -.03 for the control group. Thus, there was no indication of a speed-accuracy trade-off in either group.

It is of interest to note that there was a significant negative correlation between the TOM1 and each of the drawing scores for the children who were clumsy (see Table 4, above the diagonal line of dashes), whereas there were no such significant correlations for the control group (see Table 4, below the diagonal line of dashes).

In order to examine whether the difficulty of the stimulus patterns was similar for the two groups of children, we rank ordered the stimulus patterns by their drawing scores from lowest to highest for each group separately. The rank order correlation between the two was SO, p < .05. This moderate correlation suggests that there was a common tendency for both groups to have difficulty with the same stimulus patterns.

Discussion The aim of the experiment was to investigate the possible involvement of a visual memory deficit in the motor impairment of children who are clumsy. Children drew geometric patterns that were seen as a whole or sequentially, either immediately after

Impairment of Visuai Memory 187

Table 4 Correlations Between Variables for the Clumsy and Control Grotlps

Draw C Draw 0 Draw 15 RTC RTO RT15 Age SPM TOMI

Draw C Draw 0 Draw 15 RTC RTO RT15 Age SPM TOM1

Note. The correlations for the clumsy group are given below the diagonal line of dashes; those for the control group are given above. Draw C = drawing score on copying trials; Draw 0 = drawing score on reproduction trials at 0 delay; Draw 15 = drawing score on reproduction trials at 15-s delay; RTC = response time on copying trials; RTO = response time on reproduction trials at 0 delay; RT15 = response time on reproduction trials at 15-s delay; Age = chronological age; SPM = Standard Progressive Matrices percentile score; TOMI = score on Test of Motor Impairment. *p < .05 **p < .01

presentation or after a 15-s delay. The major finding was that while there was no difference between the two groups in immediate recall, the recall of the children who were clumsy but not of control children declined after a delay. These findings are consistent with the hypothesis that the visual memory of children who are clumsy is inferior to that of children who are not motorically impaired.

In order to be reproduced accurately, information about the patterns must be encoded and its representation stored in memory; it must also be translated into a corresponding motor output. The finding that the reproductions of the two groups did not differ on immediate recall indicates that similar pattern information was encoded, stored at least for the time taken to reproduce the figure (M = 15.72 s), and translated into a similar output. The groups differed neither in their ability to copy nor in their ability to immediately reproduce the patterns. It is likely that copying is not a sensitive test of transfer of information from the visual to the kinesthetic modality (ConnolIy & Jones, 1970; Jones & Connolly, 1979), since the continued presence of the visual stimulus allows for renewal of the kinesthetic representation.

However, the similarity of performance on immediate reproduction indicates that children who were clumsy were equally able to translate a stored visual representation into a matching motor output. This was so both when the pattern, presented in its entirety, provided an extended retinal image and when a representation of the pattern had to be constructed from the piecemeal segments made available over time. The fact that mode of presentation did not interact with the effects of either group or delay suggests that the key deficit is not to be found in the nature of the encoding and representational processes. It also excludes an interpretation of the clumsy group's vulnerability to delayed recall in terms of increased task difficulty. It is clear that the addition of a delay

188 Dwyer and McKenzie

between completion of stimulus presentation and the beginning of drawing was crucial in differentiating the performance of the two groups and that memory processes beyond those required for "immediate" reproduction are implicated in the inferior performance of the clumsy group after the delay.

In their crossmodal study of transfer of shape information between the visual and haptic modalities, Newnham and McKenzie (in press) found that only visual-to-haptic transfer distinguished children who were clumsy from controls. Control children took longer to respond and were more accurate in their judgments in the visual-haptic condition, but there were no differences between groups in the haptic-visual condition. Newnham and McKenzie argued that these results suggested that visual but not haptic memory of shape was more fragile in the children who were clumsy. The results of the experiment reported here are consistent with this interpretation in that a fading visual representation of the patterns would reduce the information available for error detection and correction of motor output.

The reproductions of control children were as accurate after delayed as after immediate recall. This suggests that pattern information was maintained in memory through visual rehearsal and raises the possibility that children who are clumsy are deficient in this respect. Dewey's (1991) findings with regard to differential accuracy in the production of motor sequences that were modeled are also in accord with this suggestion. This outcome would be expected if visual rehearsal strategies of children who were clumsy were inefficient. Further research directed toward examination of the role of visual rehearsal in the memory of children who are clumsy is clearly warranted. It would be of particular interest to compare the drawings of children who are clumsy and control children with and without articulatory suppression during the delay between presentation and reproduction of the stimulus pattern. An interaction between subject group and activity during the delay would strengthen the interpretation that visual rather than verbal rehearsal or central executive processes were implicated.

The finding of greater rapidity and inaccuracy in responding by the children who were clumsy was obtained both by Newnham and McKenzie (in press) and in the study reported here. While it is tempting to conclude that greater accuracy was associated with longer response times, there was no evidence that this was the case in graphic reproduction. The overall correlation between response duration and drawing score in both groups was trivial, and there was certainly no indication of a differential trade-off between speed and accuracy by children who were clumsy.

In summary, children who were clumsy were found to reproduce geometric patterns as accurately as control children when there was no delay between presentation and recall. They were notably less accurate after a 15-s delay. It is suggested that inefficient visual rehearsal strategies may be responsible for their poor performance.

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Acknowledgements

We thank the staff and children from Carey Baptist Grammar School and Ivanhoe Grammar School for their participation in this research program, and K.T. Ng for statistical advice.