CLUMSINESS AND PERCEPTUAL PROBLEMS IN CHILDREN WITH SPECIFIC LANGUAGE IMPAIRMENT R . P. Powell D. V . M. Bishop
Specific language impairment ( x i ) (also known as ‘developmental speech and language disorder’ or ‘developmental dysphasia’) by definition excludes children with generally reduced cognitive ability. In the third revision of the Diagnostic and Statistical Manual (DSM-III-R) of the American Psychiatric Association (1987), the disorder is defined in terms of the discrepancy between the child’s linguistic skills and general cognitive abilities, as assessed on a non-verbal intelligence scale. However, in a review of the reported cognitive levels of children with developmental dysphasia, Benton (1978) concluded that, despite the exclusion of children with clearly subnormal scores on standardised performance tests, ‘dysphasic children show greater than normal variability in “general intelligence”, as well as a group trend towards a lower than expected IQ’ (p. 47). One area in which non-verbal deficits frequency have been noted is motor skills, with several studies reporting a relationship between specific language impairment and clumsiness (e.g. Mellor 1981, Stark and Tallal 1981, Paul et al. 1983, Robinson 1987, Noterdaeme et al. 1988). Bishop and Edmundson (1987) found that on a peg-moving task, language-impaired children had no evidence of frank neurological abnormalities, but their performance was slow in relation to that of a normal control group; and
there was a significant association between the slowness of peg-moving and severity of language impairment, which was maintained when children were followed over time. The significance of such a trend among children with a supposedly specific language impairment needs to be investigated further. Are clumsiness and language difficulties common indicators of a single underlying deficit, or does their cooccurrence merely reflect involvement of neighbouring brain areas? In adults, acquired aphasia and apraxia are associated with damage to the left hemisphere (Heilman 1979), so it seems plausible that a developmental dysfunction of the left hemisphere might lead to both language and motor impairment. However, if this were the explanation, we would expect to find asymmetric motoi impairment in this population, with the right side of the body more severely affected than the left, but this is not the case (Johnston et al. 1981, Noterdaeme et al. 1988, Bishop 1990). Stark and Tallal (1981) have argued that the motor deficits of SLI children are indicative of an inability to process information at a normal rate, which affects all modalities. Those authors have shown that, consistent with their hypothesis, SLI children are impaired on tasks involving perception and production of rapidly changing stimuli, including auditory and
No\
2
755
u m 00 00
m
a m
756
visual perceptual tasks, as well as speech and motor sequencing activities. They found no difference between SLI and normal children in the ability to balance on one leg. Another approach to understanding developmental clumsiness has been adopted in the study of so-called ‘clumsy children’, most of whom do not have language deficits. The ‘clumsy child’ is defined by Gubbay (1975) as one whose ability to perform skilled movement is impaired, despite normal intelligence and normal findings in a conventional neurological examination. The characteristics of clumsy children have been investigated by Henderson and Hall (1982), who concluded that they are not a homogeneous group. Nevertheless, if children with neurological disease and mental retardation are excluded, some general conclusions seem possible. Hulme et af. (1982) found that clumsy children were poor at making visual judgements of length, and this deficit could not be explained in terms of poor motor control of the eyes. Lord and Hulme (1987) found consistently poorer performance by clumsy children in the processing of visuo-spatial information, unrelated to variance in visual acuity. They concluded that the motor problems of these children were partly a consequence of imperfect visuo-spatial perception. It is worth noting that the perceptual deficits reported by Lord and Hulme were found with static visual stimuli, so could not be explained in terms of the type of rate-. processing limitation proposed by Stark and Tallal (1981). The present study was designed to investigate further the nature of motor impairments of SLI children, using a subset of the motor and perceptual tasks described by Lord and Hulme (1987), to distinguish between three possible explanations. According to the left hemisphere dysfunction hypothesis, we would expect to find lateralised impairments on motor tasks and normal performance on visual discrimination tasks. According to the slow rate of processing hypothesis of Stark and Tallal, we would expect motor deficits to be found only in activities that involve the production of rapidly changing movements; perceptual deficits
are not predicted for visual discrimination tasks involving static stimuli or for motor tasks such as balancing that do not involve rapid movements. The imperfect visual perception hypothesis predicts that SLI children will resemble clumsy children in having deficits in visual discrimination tasks, as well as motor tasks, with both static and transient components. Method
Subjects Two groups of 17 children (13 boys and four girls) between six and 12 years took part in the study. Children in the language-impaired group were recruited from speech and language units attached to schools in the Greater Manchester area, and from a Manchester school for children with speech and language disorders. Children with sensorineural hearing-loss, epilepsy, physical disability or infantile autism were excluded, as were those born more than three weeks preterm, weighing 1.33 SD below the mean in either receptive or expressive language. Of 20 potential children, nine were included on the basis of receptive language disability, with standardised scores of c 80 on the British Picture Vocabulary Scale (BPVS)(Dunn et af. 1982). Language-impaired children who scored above this level were administered the Action Picture Test (APT, third revision) (Renfrew 1988), of whom a further eight were considered to have expressive language disability on the basis of low Information and/or Grammar scores. No child in the language-impaired group had been labelled ‘clumsy’ or referred to medical services because of motor difficulties.
TABLE I Mean (SD)age, BPVS, WISC-R Verbal and Performance subtests
‘c)
P \o
‘c)
P
Language-impaired ( N = 17) Mean (SO)
Control ( N = 17) Mean ~
Age BPVS APT Grammar APT Information Vocabulary Similarities Block Design Object Assembly Pro-rated VIQ Pro-rated PIQ
9 yrs 3 mths 78.2 16.4. 31.9. 5.3 6.6 10.4 9.4 75.6 98.7
(1 yr 6 mths)
(15.2) (5.2) (3.5) (2.1) (3.1) (2.0) (2.0) (14.2) (11.2)
9 yrs 3 mths 96,6 30.1 37.1 10.1 10.5
10-7 10.8 101.7 104.5
(SO) ~
~~
(lyr 7 mths) (9.5) (2.1) (1 *6) (2-3) (3.4) (2.3) (3.0) (15.8) (14.0)
p
G
*Test administered only to children with scaled scores of 2 8 0 on BPVS (N=8).
Children in the control group came from three schools in Lancashire. The same exclusion criteria were applied as for the SLI group. In addition, children who had received speech therapy were excluded, as were those who scored > 1.33 SD below the mean on either the BPVS or the APT. 43 children were screened for language ability and intelligence, of whom 21 were excluded after failing to meet all the criteria. 22 children were assessed on the full battery of tests, of whom 17 were selected for inclusion in the analysis purely on the basis of matching the groups for age, non-verbal intelligence (see below) and socio-economic status (Office of Population Censuses and Surveys 1980). The means and standard deviations for age, BPVS, APT Grammar and Information scores and subtests of the Wechsler Intelligence Scale for Children-Revised (wrsc-R)(Wechsler 1976) appear in Table I. As anticipated, groups did not differ on the variables on which they had been matched, i.e. age and WISC-R performance subtests. However, the groups differed significantly on all the tests of language: BPVS, APT Grammar, APT Information and the WISC-R Vocabulary and Similarities verbal subtests (all F ratios > 12.0, p
Specific language impairment ( x i ) (also known as ‘developmental speech and language disorder’ or ‘developmental dysphasia’) by definition excludes children with generally reduced cognitive ability. In the third revision of the Diagnostic and Statistical Manual (DSM-III-R) of the American Psychiatric Association (1987), the disorder is defined in terms of the discrepancy between the child’s linguistic skills and general cognitive abilities, as assessed on a non-verbal intelligence scale. However, in a review of the reported cognitive levels of children with developmental dysphasia, Benton (1978) concluded that, despite the exclusion of children with clearly subnormal scores on standardised performance tests, ‘dysphasic children show greater than normal variability in “general intelligence”, as well as a group trend towards a lower than expected IQ’ (p. 47). One area in which non-verbal deficits frequency have been noted is motor skills, with several studies reporting a relationship between specific language impairment and clumsiness (e.g. Mellor 1981, Stark and Tallal 1981, Paul et al. 1983, Robinson 1987, Noterdaeme et al. 1988). Bishop and Edmundson (1987) found that on a peg-moving task, language-impaired children had no evidence of frank neurological abnormalities, but their performance was slow in relation to that of a normal control group; and
there was a significant association between the slowness of peg-moving and severity of language impairment, which was maintained when children were followed over time. The significance of such a trend among children with a supposedly specific language impairment needs to be investigated further. Are clumsiness and language difficulties common indicators of a single underlying deficit, or does their cooccurrence merely reflect involvement of neighbouring brain areas? In adults, acquired aphasia and apraxia are associated with damage to the left hemisphere (Heilman 1979), so it seems plausible that a developmental dysfunction of the left hemisphere might lead to both language and motor impairment. However, if this were the explanation, we would expect to find asymmetric motoi impairment in this population, with the right side of the body more severely affected than the left, but this is not the case (Johnston et al. 1981, Noterdaeme et al. 1988, Bishop 1990). Stark and Tallal (1981) have argued that the motor deficits of SLI children are indicative of an inability to process information at a normal rate, which affects all modalities. Those authors have shown that, consistent with their hypothesis, SLI children are impaired on tasks involving perception and production of rapidly changing stimuli, including auditory and
No\
2
755
u m 00 00
m
a m
756
visual perceptual tasks, as well as speech and motor sequencing activities. They found no difference between SLI and normal children in the ability to balance on one leg. Another approach to understanding developmental clumsiness has been adopted in the study of so-called ‘clumsy children’, most of whom do not have language deficits. The ‘clumsy child’ is defined by Gubbay (1975) as one whose ability to perform skilled movement is impaired, despite normal intelligence and normal findings in a conventional neurological examination. The characteristics of clumsy children have been investigated by Henderson and Hall (1982), who concluded that they are not a homogeneous group. Nevertheless, if children with neurological disease and mental retardation are excluded, some general conclusions seem possible. Hulme et af. (1982) found that clumsy children were poor at making visual judgements of length, and this deficit could not be explained in terms of poor motor control of the eyes. Lord and Hulme (1987) found consistently poorer performance by clumsy children in the processing of visuo-spatial information, unrelated to variance in visual acuity. They concluded that the motor problems of these children were partly a consequence of imperfect visuo-spatial perception. It is worth noting that the perceptual deficits reported by Lord and Hulme were found with static visual stimuli, so could not be explained in terms of the type of rate-. processing limitation proposed by Stark and Tallal (1981). The present study was designed to investigate further the nature of motor impairments of SLI children, using a subset of the motor and perceptual tasks described by Lord and Hulme (1987), to distinguish between three possible explanations. According to the left hemisphere dysfunction hypothesis, we would expect to find lateralised impairments on motor tasks and normal performance on visual discrimination tasks. According to the slow rate of processing hypothesis of Stark and Tallal, we would expect motor deficits to be found only in activities that involve the production of rapidly changing movements; perceptual deficits
are not predicted for visual discrimination tasks involving static stimuli or for motor tasks such as balancing that do not involve rapid movements. The imperfect visual perception hypothesis predicts that SLI children will resemble clumsy children in having deficits in visual discrimination tasks, as well as motor tasks, with both static and transient components. Method
Subjects Two groups of 17 children (13 boys and four girls) between six and 12 years took part in the study. Children in the language-impaired group were recruited from speech and language units attached to schools in the Greater Manchester area, and from a Manchester school for children with speech and language disorders. Children with sensorineural hearing-loss, epilepsy, physical disability or infantile autism were excluded, as were those born more than three weeks preterm, weighing 1.33 SD below the mean in either receptive or expressive language. Of 20 potential children, nine were included on the basis of receptive language disability, with standardised scores of c 80 on the British Picture Vocabulary Scale (BPVS)(Dunn et af. 1982). Language-impaired children who scored above this level were administered the Action Picture Test (APT, third revision) (Renfrew 1988), of whom a further eight were considered to have expressive language disability on the basis of low Information and/or Grammar scores. No child in the language-impaired group had been labelled ‘clumsy’ or referred to medical services because of motor difficulties.
TABLE I Mean (SD)age, BPVS, WISC-R Verbal and Performance subtests
‘c)
P \o
‘c)
P
Language-impaired ( N = 17) Mean (SO)
Control ( N = 17) Mean ~
Age BPVS APT Grammar APT Information Vocabulary Similarities Block Design Object Assembly Pro-rated VIQ Pro-rated PIQ
9 yrs 3 mths 78.2 16.4. 31.9. 5.3 6.6 10.4 9.4 75.6 98.7
(1 yr 6 mths)
(15.2) (5.2) (3.5) (2.1) (3.1) (2.0) (2.0) (14.2) (11.2)
9 yrs 3 mths 96,6 30.1 37.1 10.1 10.5
10-7 10.8 101.7 104.5
(SO) ~
~~
(lyr 7 mths) (9.5) (2.1) (1 *6) (2-3) (3.4) (2.3) (3.0) (15.8) (14.0)
p
G
*Test administered only to children with scaled scores of 2 8 0 on BPVS (N=8).
Children in the control group came from three schools in Lancashire. The same exclusion criteria were applied as for the SLI group. In addition, children who had received speech therapy were excluded, as were those who scored > 1.33 SD below the mean on either the BPVS or the APT. 43 children were screened for language ability and intelligence, of whom 21 were excluded after failing to meet all the criteria. 22 children were assessed on the full battery of tests, of whom 17 were selected for inclusion in the analysis purely on the basis of matching the groups for age, non-verbal intelligence (see below) and socio-economic status (Office of Population Censuses and Surveys 1980). The means and standard deviations for age, BPVS, APT Grammar and Information scores and subtests of the Wechsler Intelligence Scale for Children-Revised (wrsc-R)(Wechsler 1976) appear in Table I. As anticipated, groups did not differ on the variables on which they had been matched, i.e. age and WISC-R performance subtests. However, the groups differed significantly on all the tests of language: BPVS, APT Grammar, APT Information and the WISC-R Vocabulary and Similarities verbal subtests (all F ratios > 12.0, p
