Running head: DEVELOPMENTAL COORDINATION DISORDER AND SPECIFIC LANGUAGE IMPAIRMENT Comparing Language Profiles: Children with Specific Language Impairment and Developmental Coordination Disorder

Background: Although it is widely recognized that substantial heterogeneity exists in the cognitive profiles of children with Developmental Coordination Disorder (DCD), very little is known about the language skills of children with a relatively pure DCD. Aims: This study compared the language abilities of children with DCD to a group whose language impairment has been well described, children with Specific Language Impairment. Methods & Procedures: Eleven children with DCD, and 11 with SLI completed standardized and nonstandardized assessments of vocabulary, grammatical skill, nonword repetition, sentence recall, story retelling, and articulation rate. Performance on the nonstandardized measures was compared to a group of typically developing children of the same age. Outcomes & Results: Children with DCD were impaired on tasks involving verbal recall and story retelling. Almost half of those in the DCD group performed similarly to the children with SLI over several expressive language measures, while 18% had deficits in nonword repetition and story retelling only. Poor nonword repetition was observed for all members of both the DCD and SLI groups. The articulation rate of the children with SLI was slower than that of the DCD group, which was slower than that of typically developing children. Conclusions: Language impairment is a common co-occurring condition in DCD. The language profile of children with either DCD or SLI was similar in the majority of, but not all, cases. Comparing Language Profiles: Children with Specific Language Impairment and Developmental Coordination Disorder Approximately 6% of children fail to develop coordinated movement skills in a manner similar to other typically developing children (Mandich & Polatajko, 2003). These children have Developmental Coordination Disorder (DCD), characterized by marked motor impairment that affects functioning in daily activities (American Psychiatric Association, 1994) in the absence of intellectual or neurological dysfunction. Although it is widely recognized that substantial heterogeneity exists in the cognitive and language profiles of children with DCD (Kaplan, Wilson, Dewey, & Crawford, 1998; Piek & Dyck, 2004; Visser, 2003; Wilson, 2005), very little is known about the language profiles of children with relatively pure DCD. The purpose of the present study was to describe the language skills of children with relatively pure DCD, and to provide a comparison with a group whose language impairment has been well described, children with Specific Language Impairment (SLI). Various terms such as developmental dyspraxia, minimal brain dysfunction, perceptual-motor dysfunction, physical awkwardness, and clumsiness have been used to describe children with motor coordination difficulties for decades (Cratty, 1994; Gubbay, 1978; Henderson, 1987). At an International Consensus Conference on Children and Clumsiness (Polatajko, Fox, & Missiuna, 1995), experts from around the world agreed that common nomenclature was essential and recommended that the term Developmental Coordination Disorder (DCD) should be used when referring to children with such motor difficulties. DCD is described in the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM-IV, 1994) as a motor coordination disturbance that significantly hinders activities of daily living and/or school performance and is not the result of another physical disability. Although it was once believed that such clumsiness was due to maturational lag (Gubbay, 1978), it is now recognized that DCD is associated with a life-long disability (Cantell, Smyth, & Ahonen, 1994). The conceptualization of DCD put forward by the DSM-IV represents the best available classification system for the disorder at present (Henderson & Barnett, 1998; Sugden & Wright, 1998). Geuze, Jongmans, Schoemaker, and Smits-Engelsman (2001) recently reviewed the criteria employed to select children with developmental motor problems in 176 publications and recommended the following criteria for identifying children with DCD for research purposes: (1) a score above 69 on a test of intelligence, and (2) performance below the 15 th centile on a standardized test of fine and gross motor performance to detect motor problems although a more stringent criteria of below the 5 th centile may be adopted in experimental research designs. These authors report that the Movement Assessment Battery for Children (M-ABC; Henderson & Sugden, 1992) is not only the most widely employed motor test for this purpose, but it is also the most appropriate to assess the DSM-IV criteria for DCD. It is widely recognized that the symptoms and severity of DCD vary from child to child (Henderson, 1987; Willoughby & Polatajko, 1995). Indeed, DCD has been associated with articulation problems (e.g., Cermak, Ward, & Ward, 1986), Attention Deficit Disorder (e.g., Kaplan, Crawford, Wilson, & Dewey, 1997), learning disabilities (e.g., Kaplan et al., 1998), dyslexia (e.g., Geuze & Kalverboer, 1994), and developmental language disorder (e.g., Fletcher Flinn, Elmes, & Strugnell, 1997). The substantial heterogeneity that exists in the cognitive profiles of children with DCD has led to the suggestion by some researchers that comorbid deficits in DCD is the norm rather than the exception (Kaplan et al., 1998; Piek & Dyck, 2004; Wilson, 2005). Several studies have attempted to uncover subtypes among children with DCD (e.g., Dewey & Kaplan, 1994; Wright & Sugden, 1996). Although no consensus has been reached, several studies have identified a group of children with DCD with a generalized sensorimotor deficit who have a particularly high rate of additional co-occurring deficits (Visser, 2003). It is of particular interest to examine groups of children with DCD with or without co-occurring deficits in order to improve our understanding of DCD (Visser, 2003). In the present study, we describe a group of children with DCD without cooccurring receptive language deficits. Although the working memory profiles of this group have been described elsewhere (Alloway & Archibald, in press), the language abilities of this group of children with relatively pure DCD were of particular interest in the current work. Despite the exclusion of children with receptive language deficits from the DCD group in this study, we hypothesized that this group may still present with atypical abilities in some language domains. Two lines of evidence led us to this prediction: First, this group of children with DCD were found to have short-term and working memory deficits in both the verbal and visuospatial domains (Alloway & Archibald, in press). Several studies have demonstrated close and specific associations between verbal short-term memory measures and vocabulary (e.g., Gathercole, Willis, Emslie, & Baddeley, 1992). In addition, links have been found between working memory and other aspects of language such as spoken narrative skills (Adams & Gathercole, 1996), utterance length and range of syntactic constructions used (Adams & Gathercole, 1995, 2000), sentence repetition (Willis & Gathercole, 2001), and language comprehension (e.g., King & Just, 1991). Even visuospatial short-term memory may support the comprehension of spatial terms in language (Phillips, Jarrold, Baddeley, Grant, & Karmiloff-Smith, 2004), and the early stages of learning to write (Manso, & Ballesteros, 2003) and decode (Meyler, & Breznitz, 1998). Secondly, heterogeneity in language profiles characterizes groups with other developmental pathologies such as children with developmental language impairments who typically have relative strengths in vocabulary and deficits in grammatical skills (Leonard, 1998). Very little is known about the language abilities of children with DCD. Two studies have examined gesture use, a language task that also taps motor skills, and found children with DCD to be impaired (Hill, Bishop, Nimmo-Smith, 1998; Zoia, Pelamatti, Cuttini, Casotto, & Scabar, 2002). Findings of particular difficulty with verbal requests for a gesture (Zoia et al., 2002) suggest that the deficits cannot be entirely accounted for by a motor impairment alone. It may be then, that children with a relatively pure DCD also have deficiencies in one or more aspects of language, and it was the aim of the present study to investigate this. Of particular interest is whether the language profile of children with DCD is similar to that of children with SLI. A key issue in the field of language disorders is whether the profiles of language deficit among children with different kinds of disorders are similar suggesting a common mechanism, or unique raising the possibility of differential underlying deficits. In a study of children with a variety of neurological abnormalities including fragile X, Sotos syndrome, congenital hydrocephalus, and congenital left hemisphere infact, Levy (2003) reported that grammatical development in the early phases (mean length of utterance 3 or under) was not diagnostic of disorder type. Although these neurological conditions are not directly comparable to the developmental pathologies described in the present work, this finding may suggest that a common language deficit underlies several disorders. In older children, however, differing profiles of morphosyntactic skills have been reported in comparisons of children with SLI and William’s Syndrome (Clahsen & Temple, 2003), and children acquiring a second language (Paradis & Crago, 2000). SLI is a relatively common developmental condition in which a child fails to develop language at the typical rate despite normal general intellectual abilities, adequate exposure to language, and in the absence of hearing impairments. There has been some consensus in recent years regarding the criteria for identifying research participants with SLI after an influential study by Records and Tomblin (1994) indicating that SpeechLanguage Pathologists agreed on the diagnosis of SLI for individuals scoring at least 1.25 standard deviations below the mean on composite language measures. Exclusion criteria include performance below age level on tests of nonverbal abilities or articulation, or the presence of hearing impairment, Autism Spectrum Disorder, or other developmental pathology that could account for the language learning disability. As well, many research groups include only those individuals with deficits in both expressive and receptive language abilities (e.g., Stark & Tallal, 1988; Rice & Oetting, 1993). Even with fairly stringent criteria, however, considerable heterogeneity exists in the profiles of children with SLI both within the realm of language and across other domains. Lexical, grammatic, and syntactic skills may all be impaired to some degree, although the extent of the deficit in any area varies across individuals. As well, SLI deficits have been reported in nonlinguistic tasks such as problem solving (e.g., Ellis Weismer, 1991) and attention (e.g., Niemi, Gundersen, Leppasaari, & Hugdahl, 2003). Even motor impairments have been found to be more common amongst children with SLI (e.g., Hill, 2001), although the motor impairments tend to occur in children with SLI who also have speech production deficits (Bishop, 2002). Despite the heterogeneity, a number of tasks do differentiate children with SLI. For example, story retelling has been found to be the best predictor of overall prognosis in both preschool and school age children with SLI (Bishop & Edmundson, 1987; Botting, Faragher, Simkin, Knox, & Conti-Ramsden, 2001). Two measures have been proposed as clinical markers of the disorder: verb tense and agreement (Leonard, Miller & Gerber, 1999; Rice & Wexler, 1996), and nonword repetition (Bishop, North, & Donlan, 1996; Dollaghan & Campbell, 1998; Gathercole & Baddeley, 1990). It remains unclear whether these tasks are sensitive to a specific impairment as reflected by relatively greater deficits in children with SLI than children with other developmental conditions affecting language, or to a general language delay with impairments present across disorder types. In the case of poor nonword repetition, decrements have been reported for a variety of groups including individuals with specific reading disabilities (e.g., Snowling, 1983; Swanson & Berninger, 1995), and Down’s syndrome (e.g., Laws, 2004). The present study compared groups of school-age children with either SLI or DCD on a battery of language measures. One aim was to describe the language profile of children with a relatively pure DCD, who had age-appropriate receptive language skills. Intact linguistic abilities across several measures would be consistent with a specific impairment in motor coordination, whereas a mixed language profile would suggest that a more general deficit is characteristic of the disorder. A second goal was to compare the language profiles of DCD and SLI. Similar strengths and weaknesses across language domains would highlight commonalities in the language skills of the two groups, whereas areas of difference would point to unique underlying mechanisms. Method