cross-modal matching by spastic children

Develop. Men. Child Neirrol. 1974, 16, 40-46

Cross-modal Matching by Spastic Children Bill Jones" Richard Alexander

Introduction Birch and Belmont (1965) have argued

that failures of intersensory integration may underlie the wide range of perceptual and perceptuo-motor deficits apparently suffered by those with cerebral palsy (see Abercrombie 1964). They stress the unity of perception and movement, following Sherrington's ( 1 947) suggestion that the motor cortex is an anatomical pathway between the senses. Jones (1972. 1973) has provided evidence of the importance for non-handicapped children of motor efferent involvement in the visual recogni- tion of form and extent and in auditory localization. I n the cerebral palsied the relationship between motor handicap and impairment of perceptuo-motor performance may sometimes be slight ( ~ . g . Nielsen 1966), though there is some evidence that perceptual skills not directly involving motor control may depend upon experience of independent mobility, par- ticularly when there is little possibility of cognitive compensation (c>.g. Wedell c t ill. 1972). Consequently there is some bahis for Birch and Belmont's basic assumption which, in itself, implies that the distinction between perceptual and perceptuo-motor abilities is no more than a matter of experimental operations.

However, the experimental test which Birch and Belmont provide is inadequate.

They argued that the cerebral palsied were handicapped in intersensory integration because they made more errors in auditory-visual cross-modal matching (CMM). As Bryant (1968) has pointed out, this conclusion does not follow. Errors in CMM

have at least two possible causes: a failure of intersensory integration or an inability to make correct discriminations within either of the modalities involved. The necessary experimental control requires comparison of the two possible CMM conditions with performance in both within- modal matching (WMM) tasks. Further, the tasks used by Birch and Belmont assimi- lated auditory skills to temporal discrimination (a rhythmic pattern was tapped out) and visual skills to spatial discrimination (the child had to select the correct match from a number of Morse-code-like printed patterns). Therefore the cerebral palsied child's poorer performance may reflect only an inability or unwillingness to judge temporal and spatial patterns to be equiva- lent. Goodnow (1971) has shown that the major change with age in matching visual to auditory patterns is the realization on the part of older children that a spatial interval can conventionally represent a time interval.

Finally, the data reported by Birch and Belmont are confounded by the choice of number of correct responses as the de-

Department of Psychology, University of Queensland, St. Lucia, Queensland 4067, Australia. * Przwnr a(fdrc,.ss: Department of Psychology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.

40

BILL JONES RICHARD ALEXANDER

Years 1 CA range

84-11.6 5.4- 8 . 1

pendent variable. Given that the subject has to distinguish between patterns in terms of ‘same’ or ‘different’, there are four possible outcomes. He can report ‘same’ when the patterns were the same (s/s), ‘same’ when they were different (s/D), ‘different’ when they were the same (D/S), or ‘different’ when they were different (DID). The theory of signal detection applied to perceptual abilities (e.g. Green and Swets 1966) makes it obvious that different subjective strategies can change the pattern of errors made by each individual. Analysis of correct responses (i.e. s/s = D/D) essentially con- founds effects of sensitivity with response bias-the probability that, independent of the stimulus, all responses may not be equally likely. Bias does not imply that some subjects do not use words, ‘same’ and ‘different’ for example, in the ordinary way. It does imply that, in conditions of uncertainty, all subjects will guess and they may be more likely to say one thing rather than another.

In the present experiment, comparison was made between a group of spastic quadraplegic children and a non-handicapped reference group in WMM and CMM

of spatio-temporal patterns. A separate analysis was made of s/s responses (conventionally termed ‘hits’) and S/D responses (conventionally termed ‘false alarms’). Following Wedell et al. (1972), we would emphasize that the reference group is not strictly a control group. It is manifestly impossible to control at the one time all the variations which could be

Mean CA CA range Mean CA 7 . 4 5.4- 7 . 7 1 6 . 7

10.3 7.11-10.8 ~ 9 . 5 13.2 11.2- 15.1 12.8

directly relevant to the complex condition of cerebral palsy.

Method Subjects

Twenty-one children with spastic quad- riplegia (the total population at the time of such children at a day and residential school for the cerebral palsied in Brisbane) were matched with 21 non-handicapped children, (pupils at two ordinary day schools). Subjects were divided into equal sized groups (N = 7), according to mental age. Previous measures of IQ (Stanford- Binet or Wechsler) were available for the spastic groups and ACER tests were used to assess IQ in the reference group. Table I shows chronological age-ranges for each mental-age group. It is clear from the table that the spastic group is somewhat older and has on average a lower IQ than the reference group.

Apparatus Visual signals were presented on two

small lights mounted about 5cm apart to the right and left on a small panel in front of the child. Auditory signals were presented to each ear through stereophonic headphones. Both visual and auditory signals were pre-programmed by means of a multi-channel tape system.

Stimuli Both visual and auditory spatio-tem-

poral patterns were made up of two signals to the right and two to the left in a random order, giving six possible combinations of

TABLE I Chronological age (CA) range and mean CA for each mental-age group in years

I M A range 1 Spasticgroup I Referencegroup I

41

DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY. 1974. 16

1 I I I Within sirbiects

right and left events. The visual stimulus was a IOOmsec flash and the auditory stimulus was a 3200 HZ tone of the same duration. Separate stimulus events (flash or tone) occurred half a second apart, while each pattern of four events in the same modality was separated by one second.

Procediire There were four experimental condi-

tions: two within-modal, visual-visual (vv) and auditory-auditory (AA); and two cross- modal, visual-auditory (VA) and auditory- visual (AV). Matching tasks were a within- subjects variable and presentation was counterbalanced across subjects. For each subject there were 30 trials in each condition. Subjects were simply asked to say whether the two patterns were 'same' or 'different' with respect to spatio-temporal location. In all conditions the a priori probability of 'same' or 'different' was 0.5.

C (modaliiy tasks) 3 0.02 1 1.10 A \ C 3 0.01 1 0.22 B . C 6 I 0.01 0.61

6 0.01 0.57 I A x B / C

i a

Y c Q 0.5

t

I Error 108 1 0.02 I

VISUAL -VISUAL A-A Spasti.

0-0 Reference 1-0 r--+

d 0.5

5'7 8;lO HL15 MENTAL AGE RANGE

AUDITORY- AUDITORY

Results Figs. 1 and 2 show mean hit rates (the

proportion of responses s/s) and mean false alarm rates (the proportion of responses S/D) respectively. Analyses of variance (Winer 1962) for hit and for false alarm rates are given in Tables I1 and I11 respectively.

TABLE I1 Analysis of variance of hit rates

Between subjects ' I A (snastickeference) ' 1 0.13 1 1.86

I B (mental age) 2 0.03 1 0.48 A b B 2 3.47 1 49.84* Error 36 0.07 1 I Within subjects I 1 C (modality tasks) 3 0.02 1 1.10 A \ C 3 0.01 1 0.22

Error 108 1 0.02

B . C 6 I 0.01 0.61 A x B / C 6 0.01 0.57

I 1 1 * p < ,000001

AUDITORY -VISUAL VISUAL -AUDITORY

1 5-7 8-10 11-15 5)7 8:10 I l l 1 5 5-7 8-10 11-15

Fig. 1. Hit rates for each modality task condition.

AUDITORY -AUDITORY VISUAL- AUDITORY AUDITORY-VISUAL VISUAL-VISUAL , .-. Spasvi'

Fig. 2. False alarm rates for each modality task condition.

42


0.05 0.13 1 . 3 1 0.02

0.02 0.02 0.02 0.01 0.01

TABLE 111 Summary of analysis of varinnce

of false alarm rates

_____

2.31 6.15*

60.40t

1.50 1.22 1.53 0.53

Between subjects A (spastic/reference) B (mental age) A x B Error

Within subjects C (modality tasks) A x C B x C A x B x C Error

Age Range (~e.7rs)

5- I 8-10

11-15

1 2 2

36

3 3 6 6

108

Spastic group Reference group

VV AA VA AV VV AA VA AV 14.1 15.0 15.0 15 .1 18.6 18 .1 19.7 20.6 21.3 21.4 21.0 24.6 26.4 26.1 29.1 25.6 25.1 24.9 26.1 25.9 29.0 29.1 29.7 29.9

* p < . o 2 t p < 4 o o o 1

Neither analysis shows a significant difference between mental-age groups, and only for false alarms are differences between spastic and reference groups significant. In neither case was there a significant subject group x modality task interaction. In other words, what differences there are between spastic and reference groups appear in both WMM tasks and in both CMM tasks.

Since both analyses resulted in a highly significant mental age x subject group interaction, a Newman-Keuls breakdown (Winer 1962) was made of between-subjects means (i.e. modality task differences were ignored since there was no modalities main effect and none of the interactions involving modalities reached significance). This procedure showed that there were no significant differences in hit rate between subject groups at any age level. However, for both spastic and reference groups, differences between the 5 to 7 years range

and the 8 to 10 years range were significant (p < -01) but there were no significant differences between the 8 to 10 and the 11 to 15 years range in either case. For false alarms, the Newman-Keuls analysis showed that both age-group differences were significant (p < .01) for the sFastic group, though only the difference between the 5 to 7 and 8 to 10 range was significant for the reference group (p < -01). At each age level the reference group had a significantly lower false alarm rate (p < *01). The absence for both subject groups of an age x task interaction is worth comment. Birch and Belmont (1965) have argued that there may be a developmental in- crease in intersensory integration independent of changes within modalities. The present results are evidence against such a suggestion, since there is no differential development of WMM and CMM.

In order to illustrate how an analysis of correct responses can hide important differences, analysis of variance of correct responses (Table IV) is shown in Table V. Clearly, correct responses as a dependent measure are analogous to false alarms rather than to hits. A Newman-Keuls breakdown of the significant interaction showed that spastic children in the two younger groups made significantly fewer correct responses (p < -01) than the reference group, though the elder group did not differ.

Discussion Present findings fail to support Birch

and Belmont’s (1965) hypothesis that the

DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY. 1974. 16

TABLE V Analysis of variance of correct

responses

df MS F ~~ ~~~

Rc~twtvn siihiccts A (spasticreference) 1 69.42 1 .78 R (mental age) 2 45.02 2 .75 A R 2 1994.00 79.02* Error 36 25.23

I I ‘irhin si,hiecr.c (~ (modality tasks) 3 19.34 2 . 5 3 A c 3 13.70 1.79 H ’ C 6 5.72 0.75

108 7 . 6 4 3 ’ 7 5 0‘49 I 4 B C

Error

* p . . .oOM)ol

cerebral palsied are necessarily character- ized by poor intersensory functioning. Spastic children had a higher false alarm rate in all four modality tasks. The relatively poorer C M M performance of the spastic group may, therefore, be due to either or both specific visual and auditory deficiencies. It remains possible, of course, that there are additional failures of intersensory integration in the cerebral palsied which are not brought out by the use of CMM tasks. Birch and Lefford (1964) argued that CMM is an important technique for understanding changes in perceptual processes contingent upon brain damage. However, the present findings show that the results of CMM studies may not tell us very much about the differences between the handicapped and the non-handicapped ; when comparison is made with the necessary’ within-modal controls, we merely see that spastic children are less accurate across the board and no more detailed analysis seems to be possible.

( h e point which can be made from the present results is that there are developmental improvements in matching tasks, at least for the small group of spastic children studied here. In fact, spastic children in the 11 to 15 years group are about as accurate as the non-handicapped aged between eight and 10 years. Aber-

crombie ( 1 964) has emphasized that the fact that a brain-damaged child of 10 years compares well with a non-handicapped seven-year-old does not rule out the importance of brain damage per se in favour of experiential or motivational factors. Nevertheless, the present findings of increased accuracy with age for the spastic group may well mean that the poorer performance of the spastic children is due to inadequate experience of independent mobility and of abstract repre- sentation of spatial concepts. Adequate performance of spatio-temporal matching requires the efficient exercise of the concepts of right and left. Asso and Wyke (1 970) have shown for non-handicapped children that the use of spatial concepts in the abstract follows a stage in which the child can only deal efficiently with spatial concepts in the actual manipulation of objects. In other words, abstract represen- tation of spatial concepts (including the use of spatial words) probably depends upon experience of independent manipulation of objects and of independent mobility relative to objects in space. Efficient general mobility requires an ability to represent spatial relations in the abstract, e.g. in following a map or verbal directions, and such understanding requires independent mobility. As a consequence, the spastic child, who necessarily has limited experience of adequate voluntary movement, may be much slower in developing the cognitive coding strategies required for accurate retention of spatio-temporal in- formation.

Finally, it may be questioned whether anv explanation is necessary for the difference between spastic and reference groups in terms of perceptual sensitivity. Analysis of the conventional dependent measure ‘correct responses’ shows that the younger spastic group made fewer correct responses. Ordinarily, the conclusion would probably have been that spastic children have lower

44


discriminative abilities. However, the mean number of correct responses as a measure of sensitivity is not independent of bias, and since analysis of hit and false alarm values shows that spastic and reference groups differ significantly only in false alarm rates, our findings may represent only an increased bias on the part of spastic children to report ‘same’, regardless of how the stimulus was perceived. (Had there been both a higher hit rate and a lower false alarm rate for the reference group, it would have been reasonable to take hit rate as an index of sensitivity.) In general, the derivation of an index of sensitivity unconfounded by bias is never an easy matter. Signal detection procedures (e.g. Green and Swets 1966) do provide useful analytical tools, but since they re- quire extensive testing of each subject, who must be able to make confidence ratings of his own judgements, they are probably

not very practicable with handicapped children.

We have suggested an explanation of the developmental trends in hit rate and false alarm rate based on the reasonable assumption that spastic children have less experience of independent mobility and of the concrete manipulation and abstract encoding of spatial relationships. We would stress that this is not a necessary conclusion from our data, and that in fact there are no data from which a bias-free index of sensitivity in the cerebral palsied could be derived to substantiate any claim such as that the cerebral palsied have a lower perceptual sensitivity. At the moment we can only raise the methodological issues.

Acknowledgements: We wish to thank Mr. G. Swam, the Headmaster, and the staff of the Queensland School for Spastic Children.

SUMMARY Twenty-one children with spastic quadraplegia were compared with a reference group of

2 1 non-handicapped children, matched for mental age, in within- and cross-modal matching of visual and auditory spatio-temporal patterns. The results failed to support Birch and Belmont’s (1965) hypothesis that children with cerebral palsy necessarily suffer from a breakdown of intersensory integration. Rather, the spastic group was equally deficient compared with the reference group in all four matching tasks. It is argued that cross-modal matching has only limited applicability in the analysis of perceptual deficiencies in those with brain-damage. More positively, it is suggested that the poorer performance of the spastic group is a function of inexperience in independent mobility. Attention is drawn to methodological issues involved in the assumption that the cerebral palsied have a lower perceptual sensitivity than the non-handicapped merely because they make fewer correct responses.

RE?SUMI? Appariement inter-perceptiJ‘chez les IMC

21 enfants quadripligiques ont CtC comparCs 2i un groupe contrde de 21 enfants non handicap& appariCs pour l’iige mental, dans une tiiche de comparaison de patterns spatio- temporels visuels et auditifs faisant appel B des relations dans un champ perceptif unique ou multiple. Les risultats n’ont pu confirmer l’hypothbse de Birch et Belmont (1965) selon laquelle les enfants IMC prisentaient des intkgrations inter-sensorielles. En fait, le groupe des IMC prCsentait le mCme dkficience que le groupe contr8le dans les quatre tiiches d’

45

DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY. 1974, 16

a ppariement. I1 apparait donc que l’appariement, faisant appel des champs perceptifs diffdrents, est d’une portee limitee dans I’analyse des dkficiences perceptives en cas de lesions cirebrales. Plus concretement, il est suggkrk que la performance plus pauvre du groupe IMC est like a l’absence d’une mobiliti indtpendante. L’attention est attirCe sur le consequences mithodologiques d’une affirmation selon laquelle les IMC ont une sensibilitk perceptive plus basse que les non handicapis simplement parce qu’ils font moins de rCponses correctes.

ZUSAM MENFASSUNG 21 Kinder mit einer spastischen Quadriplegie wurden mit einer Kontrollgruppe von 21 gesunden Kindern gleichen Intelligenzalters verglichen mittels Untersuchungen innerhalb der Gruppe wie auch mit der Kontrollgruppe uber visuelle und auditorische ‘spatio- temporale‘ Muster. Die Ergebnisse stutzen nicht die Hypothese von Birch und Belmont ( 1965), die besagt. da8 cerebral gelahmte Kinder swangslaufig ein Versagen der intersen- sorischen Integration hab2n. Dennoch zeigte die Gruppe der Spastiker in allen vier Ver- gleichsaufgabtn mangelhafte Leistungen im Vergleich zur Kontrollgruppe. Es wird argu- mentiert, daB ein Vergleich zwischen den beiden Gruppen nur eine begrenzte Anwendbarkeit fur die Analyse mangelhafter Auffassungsfahigkeit bei Hirngeschadigten besitzt. Es ist eher zu vermuten. daB die schlechteren Ausfuhrungen der Gruppe der Spastiker eine Funktion der Unerfahrenheit in selbststandiger Bewegung sind. Es wird das methodische Vorgehen unter dem Aspekt kritisch diskutiert, dalj die Kinder mit Cerebralparesen eine geringere Auffasungsfahigkeit als die nicht geschadigten besitzen nur, weil sie seltener richtige Antworten geben.

REFERENCES Abercrombie, M. L. J. (1964) Perceptiial arid Visiioniotor Disorders in Cerebral Palsy. Clinics in Develop-

Asso. D., Wyke, M. (1970) ‘Visual discrimination and verbal comprehension of spatial relations by young

Birch, H. G., Belmont, L. (1965) ‘Auditory-visual integration in brain-damaged and normal children.’

_ _ Lefford, A. (1964) ‘Two strategies for studying perception in ‘brain-damaged’ children.’ In Birch,

Bryant, P. E. (1968) ‘Comments on the design of developmental studies of cross-modal matching and cross-

Goodnow, J . J . (1971) ‘Matching auditory and visual series: modality problem or translation problem.’

Green, D. M., Swets, J. (1966) Signal Detection Theory andPsychophysics. New York: Wiley. Jones, B. (1972) ‘Facilitation of visual perception by voluntary movement in elementary school children.’

-( 1973) ‘Visual facilitation of auditory localization in children : a signal detection analysis.’ Perception

Nielsen, H. (1966) A Psvchological Study of Cerebral Palsy Children. Copenhagen: Munksgaard. Sherrington, C. S. (1947) The Integrative Aciion of the Nervous Sysfeni. Newhaven: Yale University Press. Wedell, K., Newman, C. V., Reid, P., Bradbury, I .R. (1972) ‘An exploratory study of the relationship

between size constancy and experience of mobility in cerebral palsied children.’ Dei1elopmental Medicine cind Child Neurology, 14, 61 5 .

Winer, 9. (1962) Statis:ical Analysis in Psychological Research. New York : Rinehart.

mental Medicine, No. 11. London: Spastics Society with Heinemann Medical.

children.’ British Joiirnal of Psirhology, 61, 99.

Dewlopmental Medicine and Child Neurology, I, 135.

H . G. (Ed.) Braitz Damage in Children. Philadelphia: Williams and Wilkins.

modal transfer.’ Cortex, 4, 127.

Child Development, 42, 1 187.

Journal of Experiniental Child Psychology, 14, 408.

and Psychophysics (in press).

46

cross-modal matching by spastic children

Documents