Journal of Speech and Hearing Research, Volume 34, 1106-1120, October 1991
Language Skills of Children and Adolescents With Down Syndrome: I. Comprehension Robin S. Chapman Scott E. Schwartz Elizabeth Kay-Kaining Bird University of Wisconsin-Madison
This study investigates the development of vocabulary and syntax comprehension skills cross-sectionally in 48 children and adolescents with Down syndrome (Trisomy 21), aged 5 20 years, in comparison to 48 control children aged 2-6 years matched statistically for nonverbal mental age and mother's years of education. Age-equivalent scores on vocabulary (PPVT-R) and syntax (TACL-R) comprehension tests differed in the Down syndrome group but not the control group; vocabulary comprehension was relatively more advanced than syntax Ageequivalent scores on nonverbal cognitive subtests of pattern analysis and short-term memory for bead arrangements (Stanford-Binet, 4th ed.) also differed for the Down syndrome group but not the control group, indicating an unusual pattern of nonverbal cognitive function in the Down syndrome group. Stepwise multiple regression analyses showed that chronological age and mean mental age, collectively, accounted for 78% of the variability in vocabulary comprehension and 80% of the variability in syntax comprehension in the Down syndrome group, with total passes on a hearing screening accounting for an additional 4% in each case Implications for research are discussed KEY WORDS: Down syndrome, language disorders, comprehension, mental retardation, language development
Studies of children and adolescents with Down syndrome (DS) have frequently indicated problems in expressive language development greater than one might expect on the basis of cognitive delay in nonverbal domains or comprehension skill (Andrews & Andrews, 1977; Bray & Woolnough, 1988; Cardoso-Martins, Mervis, & Mervis, 1985; Cornwell, 1974; Dodd, 1975; Gibson, 1978; Greenwald & Leonard, 1979; Harris, 1983; Hartley, 1986; Hill & McCune-Nicolich, 1981; Holdgrafer, 1981; Mahoney, Glover, & Finger, 1981; Miller, 1987, 1988; Mundy, Sigman, Kasari, & Yirmiya, 1988; Rogers, 1975; Rohr & Burr, 1978; Rosin, Swift, Bless, & Vetter, 1988; Smith & Tetzchner, 1986; Wiegel-Crump, 1981). Much less consistent is any report of problems in language comprehension, although the frequent middle ear infections and hearing loss experienced by many of the children (Brooks, Wooley, & Kanjilal, 1972; Dahle & McCollister, 1986) might lead one to expect consequent delays in language comprehension. Among mentally retarded children In general, specific deficits in comprehension, over and above cognitive delay in nonverbal problem-solving domains, are encountered frequently-in 25% (Miller, Chapman, & Bedrosian, 1978) to 60% (Abbeduto, Furman, & Davies, 1989) of the sample. For children with Down syndrome, few studies of language comprehension relative to nonverbal cognitive level exist, and the findings are inconsistent. Hartley (1982) finds poorer performance on syntactic comprehension tasks in children with Down syndrome than in children with mental retardation of other origin, matched on vocabulary comprehension. Within the Down syndrome group, poorer performance is © 1991, American Speech-Language-Hearing Association
1106
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Chapman et al.: Language Comprehension inDown Syndrome associated with a left ear advantage (and presumably right hemisphere processing) (Hartley, 1985). In contrast, Bridges and Smith (1984) report similar sentence interpretation strategies in children with Down syndrome matched for verbal comprehension on the Reynell Developmental Language Scale (Reynell, 1969) to controls. Carr (1988) reports no differences on verbal vs. expressive portions of the Reynell Test of Language Comprehension. Rosin, Swift, Bless, and Vetter (1988) have demonstrated both strengths and weaknesses in the comprehension skills of adolescent boys with Down syndrome. Communication profiles showed single-word vocabulary comprehension, as indexed by the revised Peabody Picture Vocabulary Test (Dunn & Dunn, 1981), to be as good as that of controls matched for mental age on the Columbia Test of Mental Maturities. Syntactic comprehension in children with Down syndrome, in contrast, was significantly worse than mental age matched controls or a group who were retarded for reasons other than Down syndrome. Normal hearing was a requirement for participation in the Rosen et al. study; the authors propose that the syntactic deficit is part of a general deficit in sequential processing. Other explanations for comprehension deficits could include hearing loss (Wilson, Folsom, & Widen, 1983); early otitis media (Whiteman, Simpson, & Compton, 1986); lack of early spoken language intervention programs or less than optimal mother-child interaction, sometimes mediated by medical problems or periods of hospitalization; or failure to match samples on socioeconomic status, a variable known to be associated with language skill in the normal population. Researchers finding accelerated vocabulary comprehension in DS children, as opposed to controls, have cited as sources of stimulation vocabulary enrichment or early language intervention programs or the access to a wider variety of language learning environments that is afforded the chronologically older DS children in vocational education. Variations in subject selection and control group matching procedures complicate the interpretation of these studies. Some researchers have excluded the very subjects who others argue should be the ones to have comprehension deficits. For example, those with hearing loss have been excluded; or those with histories of hospitalization have been excluded, although such periods may contribute to impoverished input or disruptions in mother-child attachment and interaction (Miller, 1988). Ages of children studied have varied; and there is some suggestion that both language and cognitive impairments may increase with age. (Or, alternatively, that measurement instruments are more sensitive at the higher levels of functioning.) Some studies have excluded children with low intelligibility. The choice of comparison groups also offers problems. Matches on expressive language are clearly inappropriate given the evidence that some DS children are expressively delayed. Matches on nonverbal cognitive level are complicated by tests that call themselves nonverbal (in response requirements) but place demands on language comprehension. Further, children with Down syndrome have been described as having short-term memory deficits in cognitive processing (although control groups in these studies, described as matched on mental age, have actually been
1107
matched on comprehension vocabulary). Many of the nonverbal tests used in nonverbal mental age matching (e.g., the Leiter, the Columbia) do not make many short-term memory demands. As syntactic comprehension tasks make such demands, it would seem appropriate to choose a control group on the basis of nonverbal cognitive tests that included some short-term memory tasks. This study investigates the variation in receptive vocabulary and syntactic comprehension in a sample of children and adolescents with Down syndrome aged 5-20 years, for whom the only exclusionary criteria were moderate hearing loss or use of signing as the primary means of communicaiton. Thus the sample should include individuals with mild hearing loss, histories of medical complications, or intelligibility problems that have been argued as possible correlates of comprehension deficit. A group of normally developing children was selected as control subjects on the basis of combined performance on one nonverbal cognitive test that included short-term memory demands and another that did not, from the same test battery (Stanford-Binet, 4th ed., Bead Memory and Pattern Analysis subtests, Thorndike, Hagen, & Sattler, 1986); both tests involved abstracted pattern matching rather than depending on school-taught content (another problem in choosing cognitive matching procedures when individuals have different educational histories). The control group was also matched for socioeconomic status; the statewide recruitment of DS children (and possibly the demographics of the older cohort that their parents are drawn from) yielded a sample lower in years of education than the city alone would be likely to yield, so recruitment of control children was extended to rural areas. We asked two questions: (a) whether children with Down syndrome differed from a control group matched for mean nonverbal cognitive level in their language comprehension skills; and (b) how well variation in comprehension skill within each group could be predicted on the basis of multiple regression analyses of the best predictors from each of six areas: chronological age, sex, cognitive level, socioeconomic status, hearing status and history, and educational history.
Method Subjects Participating inthe study were 48 children and adolescents with Down syndrome, ages 5:6 (years:months) to 20:6, and 48 children ages 2:0 to 6:0 who were developing normally (these are the same children described in Chapman, KayRaining Bird, and Schwartz, 1990). The control group mean was matched to the Down syndrome group on nonverbal mental age, as determined by mean age-equivalent score on the Bead Memory and Pattern Analysis subtests of the Stanford-Binet, 4th ed. The groups were also matched on mothers' years of education. Table 1 summarizes the groups' mean chronological age, nonverbal mental age, mothers' years of education, and sex. The children with Down syndrome were recruited from Wisconsin and northern Illinois through parent groups, per-
Downloaded From: http://jslhr.pubs.asha.org/ by a Northwestern University User on 10/06/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
1108 Journal of Speech and Heanng Research
34
1106-1120
Octoer
1991
TABLE 1. Children participating in study: Characteristics by group. Group Down syndrome (N = 48)
Characteristic
No.
Controls (N = 48)
M
SD
Boys 30 Chronological age (years) 12.54 Nonverbal mental age (years)a 4.58 Mothers' education (years) 13.33 aBased on mean of Bead Memory and Pattern Analysis *p < .05, t test of group difference sonal referrals, and the Down Syndrome Developmental Monitoring Program at the Waisman Center. All children who used speech as their primary means of communication and whose hearing showed no more than a mild loss were included in the study, up to a limit of 13 subjects in each of the 4-year age ranges between 5 1/2 and 20 1/2 years. Children were excluded if sign language was the primary means of communication or if they had a pure tone average for the frequencies 500, 1000, and 2000 Hz greater than 45 dB in the better ear. Five of the 53 Down syndrome children originally meeting the criteria were excluded for reasons of meningitis, visual impairment due to nystagmus and cataracts, a genetic record indicating mosaicism, or a genetic record indicating Down syndrome due to translocation (2). Two of the older subjects did not have genetic records of chromosomal analysis, although translocation in the parents' chromosomes had been ruled out. One of the subjects included in the oldest group had an incomplete chromosome 5 in addition to Trisomy 21 but fell within 1 standard deviation of the mean of his age group in this study in mental age measures. The control subjects were recruited from children between the chronological ages of 2 and 6 from Madison, WI, and surrounding small communities. These ages corresponded to the main range of mental age scores in the children with Down syndrome.
Procedures All children participated in a 3-hr protocol that included, in order, a hearing screening, picture descriptions, story retelling, Form L of the Peabody Picture Vocabulary Test, Revised (PPVT-R), conversation and narration with the examiner, an object hiding task (Chapman, Kay-Raining Bird, & Schwartz, 1990), the Expressive Vocabulary, Bead Memory, and Pattern Analysis subtests of the Stanford-Binet, 4th ed., conversation and snack with a parent, a speech motor evaluation, delayed story recall, event narration, the Test for Auditory Comprehension of Language, Revised (TACL-R) (CarrowWoolfolk, 1985), and the delay condition of the object hiding task. Breaks were incorporated at frequent intervals. Parent interviews elicited background data on hearing history, educational and intervention history, and parent education and occupation.
No.
M
23 4.50 4.16 1.45 4.71 1.87 13.88 subtests of Stanford-Binet, 4th
SD
p*
1 16
Language Skills of Children and Adolescents With Down Syndrome: I. Comprehension Robin S. Chapman Scott E. Schwartz Elizabeth Kay-Kaining Bird University of Wisconsin-Madison
This study investigates the development of vocabulary and syntax comprehension skills cross-sectionally in 48 children and adolescents with Down syndrome (Trisomy 21), aged 5 20 years, in comparison to 48 control children aged 2-6 years matched statistically for nonverbal mental age and mother's years of education. Age-equivalent scores on vocabulary (PPVT-R) and syntax (TACL-R) comprehension tests differed in the Down syndrome group but not the control group; vocabulary comprehension was relatively more advanced than syntax Ageequivalent scores on nonverbal cognitive subtests of pattern analysis and short-term memory for bead arrangements (Stanford-Binet, 4th ed.) also differed for the Down syndrome group but not the control group, indicating an unusual pattern of nonverbal cognitive function in the Down syndrome group. Stepwise multiple regression analyses showed that chronological age and mean mental age, collectively, accounted for 78% of the variability in vocabulary comprehension and 80% of the variability in syntax comprehension in the Down syndrome group, with total passes on a hearing screening accounting for an additional 4% in each case Implications for research are discussed KEY WORDS: Down syndrome, language disorders, comprehension, mental retardation, language development
Studies of children and adolescents with Down syndrome (DS) have frequently indicated problems in expressive language development greater than one might expect on the basis of cognitive delay in nonverbal domains or comprehension skill (Andrews & Andrews, 1977; Bray & Woolnough, 1988; Cardoso-Martins, Mervis, & Mervis, 1985; Cornwell, 1974; Dodd, 1975; Gibson, 1978; Greenwald & Leonard, 1979; Harris, 1983; Hartley, 1986; Hill & McCune-Nicolich, 1981; Holdgrafer, 1981; Mahoney, Glover, & Finger, 1981; Miller, 1987, 1988; Mundy, Sigman, Kasari, & Yirmiya, 1988; Rogers, 1975; Rohr & Burr, 1978; Rosin, Swift, Bless, & Vetter, 1988; Smith & Tetzchner, 1986; Wiegel-Crump, 1981). Much less consistent is any report of problems in language comprehension, although the frequent middle ear infections and hearing loss experienced by many of the children (Brooks, Wooley, & Kanjilal, 1972; Dahle & McCollister, 1986) might lead one to expect consequent delays in language comprehension. Among mentally retarded children In general, specific deficits in comprehension, over and above cognitive delay in nonverbal problem-solving domains, are encountered frequently-in 25% (Miller, Chapman, & Bedrosian, 1978) to 60% (Abbeduto, Furman, & Davies, 1989) of the sample. For children with Down syndrome, few studies of language comprehension relative to nonverbal cognitive level exist, and the findings are inconsistent. Hartley (1982) finds poorer performance on syntactic comprehension tasks in children with Down syndrome than in children with mental retardation of other origin, matched on vocabulary comprehension. Within the Down syndrome group, poorer performance is © 1991, American Speech-Language-Hearing Association
1106
Downloaded From: http://jslhr.pubs.asha.org/ by a Northwestern University User on 10/06/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
002 2-4685/91/3405-1106$0 1.00/0
Chapman et al.: Language Comprehension inDown Syndrome associated with a left ear advantage (and presumably right hemisphere processing) (Hartley, 1985). In contrast, Bridges and Smith (1984) report similar sentence interpretation strategies in children with Down syndrome matched for verbal comprehension on the Reynell Developmental Language Scale (Reynell, 1969) to controls. Carr (1988) reports no differences on verbal vs. expressive portions of the Reynell Test of Language Comprehension. Rosin, Swift, Bless, and Vetter (1988) have demonstrated both strengths and weaknesses in the comprehension skills of adolescent boys with Down syndrome. Communication profiles showed single-word vocabulary comprehension, as indexed by the revised Peabody Picture Vocabulary Test (Dunn & Dunn, 1981), to be as good as that of controls matched for mental age on the Columbia Test of Mental Maturities. Syntactic comprehension in children with Down syndrome, in contrast, was significantly worse than mental age matched controls or a group who were retarded for reasons other than Down syndrome. Normal hearing was a requirement for participation in the Rosen et al. study; the authors propose that the syntactic deficit is part of a general deficit in sequential processing. Other explanations for comprehension deficits could include hearing loss (Wilson, Folsom, & Widen, 1983); early otitis media (Whiteman, Simpson, & Compton, 1986); lack of early spoken language intervention programs or less than optimal mother-child interaction, sometimes mediated by medical problems or periods of hospitalization; or failure to match samples on socioeconomic status, a variable known to be associated with language skill in the normal population. Researchers finding accelerated vocabulary comprehension in DS children, as opposed to controls, have cited as sources of stimulation vocabulary enrichment or early language intervention programs or the access to a wider variety of language learning environments that is afforded the chronologically older DS children in vocational education. Variations in subject selection and control group matching procedures complicate the interpretation of these studies. Some researchers have excluded the very subjects who others argue should be the ones to have comprehension deficits. For example, those with hearing loss have been excluded; or those with histories of hospitalization have been excluded, although such periods may contribute to impoverished input or disruptions in mother-child attachment and interaction (Miller, 1988). Ages of children studied have varied; and there is some suggestion that both language and cognitive impairments may increase with age. (Or, alternatively, that measurement instruments are more sensitive at the higher levels of functioning.) Some studies have excluded children with low intelligibility. The choice of comparison groups also offers problems. Matches on expressive language are clearly inappropriate given the evidence that some DS children are expressively delayed. Matches on nonverbal cognitive level are complicated by tests that call themselves nonverbal (in response requirements) but place demands on language comprehension. Further, children with Down syndrome have been described as having short-term memory deficits in cognitive processing (although control groups in these studies, described as matched on mental age, have actually been
1107
matched on comprehension vocabulary). Many of the nonverbal tests used in nonverbal mental age matching (e.g., the Leiter, the Columbia) do not make many short-term memory demands. As syntactic comprehension tasks make such demands, it would seem appropriate to choose a control group on the basis of nonverbal cognitive tests that included some short-term memory tasks. This study investigates the variation in receptive vocabulary and syntactic comprehension in a sample of children and adolescents with Down syndrome aged 5-20 years, for whom the only exclusionary criteria were moderate hearing loss or use of signing as the primary means of communicaiton. Thus the sample should include individuals with mild hearing loss, histories of medical complications, or intelligibility problems that have been argued as possible correlates of comprehension deficit. A group of normally developing children was selected as control subjects on the basis of combined performance on one nonverbal cognitive test that included short-term memory demands and another that did not, from the same test battery (Stanford-Binet, 4th ed., Bead Memory and Pattern Analysis subtests, Thorndike, Hagen, & Sattler, 1986); both tests involved abstracted pattern matching rather than depending on school-taught content (another problem in choosing cognitive matching procedures when individuals have different educational histories). The control group was also matched for socioeconomic status; the statewide recruitment of DS children (and possibly the demographics of the older cohort that their parents are drawn from) yielded a sample lower in years of education than the city alone would be likely to yield, so recruitment of control children was extended to rural areas. We asked two questions: (a) whether children with Down syndrome differed from a control group matched for mean nonverbal cognitive level in their language comprehension skills; and (b) how well variation in comprehension skill within each group could be predicted on the basis of multiple regression analyses of the best predictors from each of six areas: chronological age, sex, cognitive level, socioeconomic status, hearing status and history, and educational history.
Method Subjects Participating inthe study were 48 children and adolescents with Down syndrome, ages 5:6 (years:months) to 20:6, and 48 children ages 2:0 to 6:0 who were developing normally (these are the same children described in Chapman, KayRaining Bird, and Schwartz, 1990). The control group mean was matched to the Down syndrome group on nonverbal mental age, as determined by mean age-equivalent score on the Bead Memory and Pattern Analysis subtests of the Stanford-Binet, 4th ed. The groups were also matched on mothers' years of education. Table 1 summarizes the groups' mean chronological age, nonverbal mental age, mothers' years of education, and sex. The children with Down syndrome were recruited from Wisconsin and northern Illinois through parent groups, per-
Downloaded From: http://jslhr.pubs.asha.org/ by a Northwestern University User on 10/06/2016 Terms of Use: http://pubs.asha.org/ss/rights_and_permissions.aspx
1108 Journal of Speech and Heanng Research
34
1106-1120
Octoer
1991
TABLE 1. Children participating in study: Characteristics by group. Group Down syndrome (N = 48)
Characteristic
No.
Controls (N = 48)
M
SD
Boys 30 Chronological age (years) 12.54 Nonverbal mental age (years)a 4.58 Mothers' education (years) 13.33 aBased on mean of Bead Memory and Pattern Analysis *p < .05, t test of group difference sonal referrals, and the Down Syndrome Developmental Monitoring Program at the Waisman Center. All children who used speech as their primary means of communication and whose hearing showed no more than a mild loss were included in the study, up to a limit of 13 subjects in each of the 4-year age ranges between 5 1/2 and 20 1/2 years. Children were excluded if sign language was the primary means of communication or if they had a pure tone average for the frequencies 500, 1000, and 2000 Hz greater than 45 dB in the better ear. Five of the 53 Down syndrome children originally meeting the criteria were excluded for reasons of meningitis, visual impairment due to nystagmus and cataracts, a genetic record indicating mosaicism, or a genetic record indicating Down syndrome due to translocation (2). Two of the older subjects did not have genetic records of chromosomal analysis, although translocation in the parents' chromosomes had been ruled out. One of the subjects included in the oldest group had an incomplete chromosome 5 in addition to Trisomy 21 but fell within 1 standard deviation of the mean of his age group in this study in mental age measures. The control subjects were recruited from children between the chronological ages of 2 and 6 from Madison, WI, and surrounding small communities. These ages corresponded to the main range of mental age scores in the children with Down syndrome.
Procedures All children participated in a 3-hr protocol that included, in order, a hearing screening, picture descriptions, story retelling, Form L of the Peabody Picture Vocabulary Test, Revised (PPVT-R), conversation and narration with the examiner, an object hiding task (Chapman, Kay-Raining Bird, & Schwartz, 1990), the Expressive Vocabulary, Bead Memory, and Pattern Analysis subtests of the Stanford-Binet, 4th ed., conversation and snack with a parent, a speech motor evaluation, delayed story recall, event narration, the Test for Auditory Comprehension of Language, Revised (TACL-R) (CarrowWoolfolk, 1985), and the delay condition of the object hiding task. Breaks were incorporated at frequent intervals. Parent interviews elicited background data on hearing history, educational and intervention history, and parent education and occupation.
No.
M
23 4.50 4.16 1.45 4.71 1.87 13.88 subtests of Stanford-Binet, 4th
SD
p*
1 16
