Linguistic and pragmatic language skills in adults with autism spectrum disorder: A pilot study

Research in Autism Spectrum Disorders 2 (2008) 176–187 http://ees.elsevier.com/RASD/default.asp

Linguistic and pragmatic language skills in adults with autism spectrum disorder: A pilot study Fiona M. Lewis a,*, Gail C. Woodyatt a, Bruce E. Murdoch b a

Division of Speech Pathology, School of Health and Rehabilitation Sciences, University of Queensland, Australia b School of Health and Rehabilitation Sciences, University of Queensland, Australia Received 21 May 2007; accepted 31 May 2007

Abstract This article reports on the linguistic and pragmatic language skills of adults with a diagnosis of autism spectrum disorder (ASD). Seventeen adults (aged 18–67 years) with a diagnosis of ASD were assessed using the Western Aphasia Battery (WAB), the Right Hemisphere Language Battery (RHLB) and the Test of Nonverbal Intelligence-Second Edition (TONI-2). Performance by the ASD participants was compared to 13 peers (aged 18–65 years) with no disability. Within-group differences for the ASD participants were examined using a hierarchical cluster analysis of performance on the WAB and the RHLB. There were significant differences between the ASD group and the control group on a number of the WAB and the RHLB subtests, but no significant difference between the two groups on nonverbal cognitive ability. Subgroups within ASD, based on language performance, could be described. Language performance, but not nonverbal cognitive skill, differentiated the ASD subgroups. Individualised language support may need to be considered in the development of employment and training services. Further research is needed to determine if language and communication difficulties are barriers to employment in adults with ASD. # 2007 Elsevier Ltd. All rights reserved. Keywords: Autism spectrum disorder; Language skills; Adults; Western Aphasia Battery; Right Hemisphere Language Battery; Vocational support

Autism spectrum disorder (ASD) is a life-long developmental disability with a neurological basis (Hill & Frith, 2003). Language and communication difficulties are central to the autistic presentation (American Psychiatric Association [APA], 1994), and numerous studies have described linguistic (e.g., Koning & Magill-Evans, 2001; Mayes & Calhoun, 2001; Shields,

* Corresponding author. Tel.: +61 7 3365 1877; fax: +61 7 3365 4754. E-mail address: [email protected] (F.M. Lewis). 1750-9467/$ – see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.rasd.2007.05.002

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

177

Varley, Broks, & Simpson, 1996; Szatmari, Archer, Fisman, Streiner, & Wilson, 1995), and pragmatic deficits (Booth, Charlton, Hughes, & Happe, 2003; Dennis, Lazenby, & Lockyer, 2001; Emerich, Creaghead, Grether, Murray, & Grasha, 2003; Losh & Capps, 2003; Ozonoff & Miller, 1996; Paul, Augustyn, Klin, & Volkmar, 2005; Rumsey & Hamburger, 1988; Shields et al., 1996; Shriberg et al., 2001) in children and adolescents with ASD. Seltzer et al. (2003) have suggested that overall use of language and nonverbal communication skills in ASD improves from childhood to adolescence, and that the pattern of improvements continue into adulthood. Howlin (1997, 2003), however, contends that most adolescents and adults with the disorder continue to exhibit language difficulties, and believes that improved services for adults are needed if long-term outcomes are to be enhanced. Seltzer et al. (2003) concur, suggesting that adults with ASD have no lesser need for services and support than children with the disorder. It is possible that support services are needed in the area of language and communication in the adult ASD population, as skill deficits in these areas have been proposed as impediments to successful psychosocial and vocational outcomes in adults with ASD (Howlin, Alcock, & Burkin, 2005). Determination of the type and level of support offered to adults with ASD requires a clinical appreciation of their communicative needs, but few studies to date have focused on the language and communication skills in adults with the disorder (Lewis, Murdoch, & Woodyatt, in press; Rumsey & Hamburger, 1988). Studies of adults with a history of childhood developmental language disorders (Clegg, Hollis, Mawhood, & Rutter, 2005; Eales, 1993) have suggested that childhood language difficulties may negatively impact upon psychosocial well being in adulthood. Clegg et al. (2005), for instance, investigated psychosocial outcomes for adults with a history of childhood developmental language disorders and found poor vocational outcomes, such as unstable work histories or long periods of unemployment, and deficits in social relationships and close friendships were associated with the adults with a history of language impairment. Eales (1993) investigated adults with a history of developmental receptive language in his study. He likewise described negative psychosocial consequences of early language impairment, in that pragmatic language deficits contributed to social impairments in the adults with a developmental history of receptive language impairment. If language difficulties reduce psychosocial outcomes for adults with histories of language disorder, but not necessarily ASD, an accurate clinical picture of the language difficulties of adults with ASD is therefore needed to determine if specific language intervention and support is warranted for this population. Although linguistic and pragmatic deficits have been identified in children and adolescents with ASD (e.g., Dennis et al., 2001; Paul et al., 2005; Shriberg et al., 2001; Szatmari et al., 1995), generalising the results from child and adolescent studies to adults should be avoided as language skills in ASD continue to change from adolescence to adulthood (Seltzer et al., 2003) and the maturational changes in language skill from childhood to adulthood are not, as yet, clearly understood in the disorder (Howlin, 1997). Recent research (Lewis et al., in press) has suggested that adults with a diagnosis of ASD experience difficulties with those high-level language skills that require a person to use and interpret language in a flexible, rational and goal-oriented manner in an ever-changing communicative environment (Wiig, 1989). Knowledge that adults with ASD may present with sub-optimal complex, metalinguistic skills does not, however, fully inform on the basic linguistic and pragmatic language difficulties experienced in daily interactions at home and at work. Studies investigating basic language skills in adults with ASD have identified only mild linguistic difficulties (Rumsey & Hamburger, 1988), and some restrictions regarding receptive and expressive semantic knowledge (Howlin, 2003). Findings by Rumsey and Hamburger and

178

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

Howlin however, may be over-estimating the basic language skills in adults with ASD. Their studies investigated a narrow range of language abilities only, thus possibly contributing an inaccurate clinical picture of the day-to-day language skills of adults with disorders on the autism spectrum. An accurate clinical understanding of language skills in adults with ASD is needed if, as proposed by Howlin (1997), receptive language deficits in adults with the disorder may reduce vocational success. Receptive language deficits have been identified in children with ASD (Koning & MagillEvans, 2001). Koning and Magill-Evans assessed children with ASD using the Clinical Evaluation of Language Fundamentals-Revised (CELF-R) (Semel, Wiig, & Secord, 1987), a comprehensive assessment of language skill. The receptive language component of CELF-R assesses skills in following increasingly complex oral directions, word classes and semantic relationships, yet assessment of receptive skills in adults with ASD (Howlin, 2003) has been restricted to the British Picture Vocabulary Scale (Dunn, Dunn, Whetton, & Burley, 1997; Dunn, Dunn, Whetton, & Pintillie, 1982), an assessment of receptive semantic skills only. Overall receptive language skills may not necessarily be determined by receptive semantic skills alone. The limited data regarding specific language difficulties in ASD may likewise be contributing to an inaccurate clinical picture of the language skills of adults with disorders on the autism spectrum. Rumsey and Hamburger’s (1988) finding of mild linguistic difficulties was based on performance on subtests of the Neurosensory Center Comprehensive Examination for Aphasia (Spreen & Benton, 1969), and the Boston Naming Test (Kaplan, Goodglass, & Weintraub, 1978). No combination of tests within the test battery, however, was identified as more discriminating than others. No specific deficits could therefore be identified. Additionally, non-homogeneity of language skills associated with the ASD presentation has been noted (Mawhood, Howlin, & Rutter, 2000; Rumsey & Hamburger, 1988), yet few studies have undertaken within-group analysis to investigate the heterogeneity within the autistic spectrum. To provide clinically relevant information that may contribute to determining the everyday, and hence, vocational communication needs of adults with ASD, within-group differences on a range of language activities should be examined. Seltzer et al. (2003) have argued that developmentally appropriate services are needed for adults with ASD diagnoses. To offer appropriate support, an accurate clinical understanding of their language and communication strengths and weaknesses is needed. Hence, the current study investigated the proficiency of a group of adults with the diagnosis on a range of linguistic and pragmatic language tasks relative to typically developing peers. Additionally, to provide clinically relevant information, hierarchical cluster analysis of the ASD participants was performed to profile the heterogeneity of these skills. Based on previous findings, it was hypothesised that performance on linguistic and pragmatic language tasks would differentiate the ASD group from the control group. Given the heterogeneity noted in previous studies, it was hypothesised that subgroups, based on linguistic and pragmatic skills within the ASD group, could be described. 1. Method 1.1. Participants Seventeen adults with average intelligence (8 male; 9 female; M age: 35 years; S.D.: 12 years; range: 18–67 years; M years of schooling: 12; range: 8–15) with a diagnosis of Asperger syndrome (AS), high functioning autism (HFA), ASD or autism (all diagnoses henceforth

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

179

referred to as ASD), were recruited through the Asperger Syndrome Support Network of Queensland, Autism Queensland, and newspaper articles. Table 1 displays the demographic details of participants. In addition to the diagnosis, inclusion criteria for the study were English as a first language, no neurological disease or trauma, no other co-morbid condition, no history of drug and/or alcohol abuse, and normal vision and hearing. Documentation of diagnosis was requested before the commencement of testing. Diagnoses made by psychiatrists and psychologists were accepted for inclusion into the study. Thirteen adults (6 males; 7 females; M age: 35 years; S.D.: 13 years; range: 18–65 years; M years of schooling: 13; range: 11–15) with non-significant developmental histories were recruited as control participants. Student t-tests indicated there were no significant differences between the control group and the ASD group on age (t = 0.040; p = 0.968) or years of schooling (t = 1.322; p = 0.197). Recruitment of control participants was through newspaper articles in local papers, and local sporting clubs in the south-east corner of Queensland. To be included in the control group, participants were required to have English as a first language, no history of Table 1 Demographic details of the ASD participants ID

Sex

Age (in yrs)

Ed level a

When diagnosed

Diag (Source)

Dev lge hist

Employment

Early intervention

1

Fe

18

Sec

Child

HFA (psychiat)

Delayed

SP

2 3 4 5 6

M M M M M

29 27 28 48 29

Sec Tert Sec Tert Post-Sec

Adult Adult Child Adult Adult

Delayed Unsure Delayed Unsure Normal

7 8 9 10 11 12 13

Fe Fe Fe M Fe Fe M

30 42 31 30 22 26 67

Post-Sec Sec Tert Tert Post-Sec Sec Post-Sec

Adult Childb Adult Adult Adult Adultc Adult

AS (psychiat) AS (psych) HFA (psychiat) AS (psychiat) AS (multi-disciplinary team: Autistic Centre AS (psychiat) Autism (psych) AS (psych) AS (psych) AS (psych) ASD (psych) AS (psych)

Supported training programme Unemployed Full-time Unemployed Full-time Unemployed

Unsure Delayed Unsure Unsure Delayed Unsure Unsure

14 15 16 17

Fe FE M Fe

38 32 48 48

Tert Sec Post-Sec Prim

Adult Adult Adult Adult

AS AS AS AS

Unsure Delayed Unsure Delayed

(psychiat) (psychiat) (psych) (psych)

Unemployed Part-time by choice Full-time parenting Full-time Unemployed Unemployed Retired from full-time work Part-time by choice Unemployed Unemployed Unemployed

SP Nil SP, Beh Nil SP Nil Beh Nil Nil SP Beh Nil Nil Nil Nil SP

Note: ASD = autism spectrum disorder, AS = Asperger syndrome; HFA = high functioning autism; Ed level = educational level. Prim = primary; Sec = secondary; Post-Sec = post-secondary vocational trade; Tert = tertiary; Diag = diagnosis; Source = source of independently given diagnosis; Psychiat = psychiatrist; Psych = psychologist; Dev lge hist = reported developmental language history; Normal = Language onset prior to age 2 years, based on the language criterion for Asperger syndrome from the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition [DSMIV]; Delayed = language onset after age 2 years using DSM-IV language criterion for Autistic Disorder; M = Male; Fe = female; Yrs = years; early intervention = type of intervention provided during childhood; SP = speech pathology intervention; Beh = behavioural intervention. a Primary education consisted of 8 years of education; Secondary consisted of 12 years of education; post-secondary vocational consisted of 11 years of education; tertiary consisted of 15 years of education. b Diagnosed as autistic at 3 years of age by a psychologist, then diagnosed as an adult as AS by a psychiatrist. c Diagnosed in childhood with a number of psychiatric disorders, then diagnosed in adulthood as AS.

180

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

neurological trauma or disease, no history of drug and/or alcohol abuse, and normal hearing and vision. In addition, to avoid co-morbidity and family links with autism and language difficulties, there was to be no family history of autism, no developmental history of language delays or difficulties, and no family history of language delays or difficulties. Of the 13 control participants, 10 were working full-time, one was a full-time parent, one had retired after life-long full-time work, and one was a full-time university student. 1.2. Measures The present study is part of a larger study examining the clinical presentation of adults with ASD and adults with right- and left-hemisphere focal brain injury. The language assessments administered, therefore, needed to be accessible to the brain-injured population. The Western Aphasia Battery (WAB) (Kertesz, 1982) and the Right Hemisphere Language Battery (RHLB) (Bryan, 1989) were chosen for the investigation of basic linguistic and pragmatic language skills. The Test of Nonverbal Intelligence-Second Edition (TONI-2) (Brown, Sherbenou, & Johnsen, 1990) was administered to determine if differences in verbal results were due to nonverbal cognitive abilities rather than linguistic and/or pragmatic factors only. For the purposes of the current study, only the language component of the WAB (Kertesz, 1982) was administered. The subtests comprising the language component are: Spontaneous Speech (Information and Fluency), Auditory Verbal Comprehension, Repetition, and Naming. Spontaneous Speech measures functional communication, and is designed to elicit conversational speech from the participant through an interview and picture description. An Information score is obtained based on the accuracy, the completeness of content, and the relevance and appropriateness of responses. The Fluency score reflects grammatical and syntactic aspects of language production. Auditory Verbal Comprehension consists of an assessment of increasingly complex comprehension tasks. The tasks include Yes/No questions, single word recognition, and the assessment of comprehension of sequential commands, where the length of the sentence and the number of clauses within the sentence increases. Repetition assesses the ability to repeat high frequency single words, composite words, high and low probability sentences, and sentences of increasing length and grammatical complexity. Naming assesses competence on confrontation naming of objects, category naming, sentence completion, and responsive speech. These subtests can be scored individually, as well as combined to provide a WAB Aphasia Quotient (WAB AQ), an index of overall linguistic skill. The WAB is standardised for the adult population, but is intended to be used for adults with brain damage. Six of the seven RHLB (Bryan, 1989) subtests were administered. These were Metaphor Picture Test, Written Metaphor Test, Comprehension of Inferred Meaning, Appreciation of Humour, Lexical Semantic Test, and Production of Emphatic Stress. The seventh RHLB subtest, Discourse Analysis, was not undertaken due to time and financial constraints. The RHLB was designed to ‘‘provide quantitative and qualitative information of language impairment following right hemisphere damage [RHD]’’ (Bryan, 1989, p. 10). It was chosen as it is one of the few assessments available that examines pragmatic skills. It is acknowledged that adults with ASD do not have focal right- or left-hemisphere brain injury. 1.3. Procedure Agglomerative hierarchical cluster analysis was undertaken, using the ASD participants’ performance scores from the WAB AQ (Kertesz, 1982) and the six RHLB subtests (Bryan, 1989),

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

181

to examine the range of skills within the ASD group. In agglomerative hierarchical clustering, individual cases are initially considered a cluster and then the two cases with the lowest distance (or highest similarity) are combined into a cluster. The case with the lowest distance to either of the first two is considered next. If that third case is closer to a fourth case than it is to either of the first two, the third and fourth cases become the second two-case cluster. If the third case is not closer to the fourth case, it is added to the first cluster. The process is repeated for each case, adding to existing clusters, creating new clusters, or combining clusters to get the final number of clusters. The rescaled distance refers to similarity in measures, and cases with a similar rescaled distance cluster early. Greater distances at which clusters combine denote greater heterogeneity within the clusters. When a horizontal line joins two vertical portions, it indicates fusion between two clusters of cases (NCSU, 2006; StatSoft, 1984–2004). Average linkage clustering (Sokal & Michener, 1958) was used for the analysis. Average linkage clustering is a relatively robust method of analysis (Everitt, Landau, & Leese, 2001) which computes an average of the similarity of a case under consideration in regards to all cases in the existing cluster. If there is a level of similarity using this average value, the case is joined to the existing cluster (Aldenderfer & Blashfield, 1984). The dendogram is a pictorial representation of the complete clustering procedure. There are a number of approaches to determining the number of groups, but Baxter (1994) has suggested informal and subjective criteria remain the most common approach. All testing was undertaken at the University of Queensland or in the home of the participant. Each assessment was administered in a distraction-free environment in a standardised manner according to the instruction manual. No time limits were placed on participant responses unless the subtest required time limits (e.g., Naming). Table 2 Descriptive statistics of the adult participants ASD (n = 17)

Controls (n = 13)

t

Significance (two-tailed)

M

S.D.

M

S.D.

TONI-2 WAB (AQ) Inform Fluency Comp Rep Naming

91 95.9 9.94 9.41 9.49 9.58 9.52

14 3.4 0.24 1.12 0.57 0.42 0.55

99 99.5 10.00 10.00 9.99 9.79 9.98

11 1.1 0.00 0.00 0.04 0.53 0.08

1.765 4.130 0.871 2.163 3.571 1.210 3.366

0.857 0.001*** 0.391 0.046 0.003** 0.237 0.004**

RHLB Met Pic Writ Met Comp Inf Mean App Humour Lex-Semantics Prod Emp Stress

52.8 53.71 41.24 46.88 57.29 45.71

9.99 7.33 7.24 12.79 8.08 6.23

60.69 57.38 52.15 58.08 62.00 55.85

0.751 3.07 4.06 6.30 0.00 2.19

3.258 1.866 5.234 3.144 2.403 6.223

0.005 0.075 0.001*** 0.004** 0.029 0.001***

Note: ASD = Autism spectrum disorder; TONI-2 = Test of Nonverbal Intelligence-Second Edition; WAB = Western Aphasia Battery; WAB (AQ) = WAB Aphasia Quotient; Inform = Information; Comp = Auditory Verbal Comprehension; Rep = repetition; RHLB = Right Hemisphere Language Battery; Met Pic = Metaphor Picture Test; Writ Met = Written Metaphor Test; Comp Inf Mean = Comprehension of Inferred Meaning; App Humour = Appreciation of Humour; LexSemantics = Lexical Semantic Test; Prod Emp Stress = Production of Emphatic Stress. ** p  0.004 (Bonferroni adjustment). *** p  0.001.

182

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

2. Results Means and standard deviations for all measures are listed in Table 2. For significance at the 0.05 level, p must be equal to or less than 0.004, as determined by the Bonferroni adjustment to correct for the multiplicity of tests (Price, 2000). No significant difference between the two groups was found on mean TONI-2 performance ( p  0.004). For each measure, a Levene’s test was carried out, and where necessary, appropriate corrections for non-homogeneity were undertaken. The Student t-test revealed significant differences between the two groups, with the adults with ASD being less proficient on the WAB AQ ( p  0.001), Auditory Verbal Comprehension ( p  0.004), Naming ( p  0.004), Comprehension of Inferred Meaning ( p  0.001), Appreciation of Humour ( p  0.004), and Production of Emphatic Stress ( p  0.001). All other measures failed to reach significance ( p  0.004 on all measures). Agglomerative hierarchical cluster analysis, based on the ASD group’s performance scores from the WAB AQ and the six RHLB subtests, was undertaken to examine language subgroupings within the ASD group. The dendogram of the clustering is shown in Fig. 1. The partitioning of the dendogram into clusters was based on informal and subjective analysis. Two descriptive subgroups can be identified. Table 3 displays the membership of the subgroups. Each participant’s score is defined as within a number of standard deviations from the control group’s mean. Performance scores within each subgroup support the partitioning decision. Subgroup 1 is characterised by mild to moderate overall linguistic difficulties, generally intact metaphorical language skills, mild to moderate difficulty with inferential language, and

Fig. 1. Agglomerative hierarchical cluster analysis of the 17 ASD adults based on performance on the Western Aphasia Battery Aphasia Quotient and the six subtests from the Right Hemisphere Language Battery.

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

183

Table 3 Subgroups of adults with ASD based on performance on the WAB AQ and the six RHLB subtests Subgroup

ID

1 (n = 10) M age: 37, 0 (yrs, mths) (S.D.: 14, 7)

5 14 16

+1 1 1

M TONI-2: 95.9 (S.D.: 10.4)

10 1 7 11 3 8 13

2 (n = 7) M age: 31, 8 (S.D.: 7, 4) M TONI-2: 84.1 (S.D.: 15.7)

WAB AQ

MP

WM

CIM

AH

LS

PES

0 2 2

+1 +1 +1

1 2 3

1 1 2

+1 +1 6

2 3 +1

2 4 2 2 2 2 +1

2 0 0 0 0 0 2

+1 2 +1 +1 +1 +1 2

1 1 3 4 0 1 2

1 2 3 1 +1 +1 +1

11 +1 +1 +1 +1 +1 +1

4 7 7 8 4 8 2

9 2

8 7

20 16

+1 4

3 6

+1 5

+1 +1

3 12

17 4 12 15 6

10 6 8 3 4

20 16 12 16 32

4 2 2 4 +1

5 3 5 3 6

4 5 4 5 5

+1 6 6 19 26

10 4 5 5 5

Note: ASD = autism spectrum disorder; WAB AQ = Western Aphasia Battery Aphasia Quotient; RHLB = Right Hemisphere Language Battery; TONI-2 = Test of Nonverbal Intelligence-Second Edition; MP = Metaphor Picture Test; WM = Written Metaphor Test; CIM = Comprehension of Inferred Meaning; AH = Appreciation of Humour; LS = Lexical Semantic Test; PES = Production of Emphatic Stress; Yrs, mths = years, months. Scores are entered as within standard deviations above or below the control mean; (+) = Above the control mean; ( ) = Below the control mean. Scores entered as 0 indicate no deviation from the control mean.

appreciation of humour, intact lexical-semantic flexibility and moderate-severe difficulties using emphatic stress to convey meaning in speech. Subgroup 2 is characterised by generally severe overall linguistic difficulties, and moderate-severe difficulties with metaphorical and inferential language, appreciation of humour, lexical semantic flexibility, and the Production of Emphatic Stress to convey meaning in speech. Non-parametric tests (Mann–Whitney U-tests) established there were no significant differences between the two ASD subgroups on the TONI-2 (Z = 1.661; p = 0.097) and age (Z = 0.588; p = 0.557). 3. Discussion The present study investigated the linguistic and pragmatic language skills of a group of adults with a diagnosis of ASD. The findings suggest that, despite presenting with comparable nonverbal cognitive skills, the adults with ASD in the present study experienced difficulties in a number of language areas relative to their peers. Additionally, an examination of performance differences within the ASD participants revealed the language skills associated with the disorder ranged from intact to severe difficulties. The findings of the current study suggest that difficulties with complex language skills (Lewis et al., in press) may not be the only restriction to language competence in adults with ASD. Basic linguistic skills, such as Auditory Verbal Comprehension skills and naming abilities, as assessed by the WAB (Kertesz, 1982), were compromised in the adults with the diagnosis involved in the study. Additionally, the ASD participants were less competent than their peers on a range of pragmatic language skills, such as understanding inference, appreciating humour and producing

184

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

emphatic stress. The current findings extend the work by previous researchers who described only mild linguistic difficulties such as expressive and receptive semantic deficits (Rumsey & Hamburger, 1988). The need for thorough language assessment of adults with a diagnosis of ASD was highlighted in the present study. A comprehensive language assessment, which identified areas of specific difficulty in the adults with ASD investigated in the study, may provide clinically relevant data that can be utilised to determine the focus of support and intervention. Previous studies of adults with developmental histories of language impairment have identified language and communication difficulties as impediments to positive psychosocial and vocational outcomes (Clegg et al., 2005; Eales, 1993). It is possible, therefore, that the linguistic and pragmatic language deficits identified in the current study may be impediments to positive psychosocial and vocational outcomes in the lives of the adults with ASD. Thirteen adults with ASD (excluding one participant who was retired, one engaged in full-time parenting, and two who elected to engage in part-time work only) and 10 control participants were in a position to engage in full-time employment. All 10 controls were employed, while only three with ASD were employed. The three employed ASD adults were tertiary qualified and working in their field of study. Most of the remaining 10 ASD adults expressed a desire to secure meaningful employment. Further research is needed to determine if linguistic and pragmatic language skills are impediments to obtaining gainful employment in the adults with ASD. The current findings offer tentative support for the non-homogeneity of language skills previously noted in ASD (Rumsey & Hamburger, 1988). Normal variation within the sample could account for some, but not all, of the heterogeneity noted in the subgroups. One subgroup possessed reasonably intact metaphorical language skills, experienced mild-moderate difficulties on overall linguistic tasks and moderate-severe difficulties on the use of emphatic stress to convey contrasting meaning. All three ASD participants engaged in full-time employment, and the retiree from full-time employment, were placed within this subgroup, suggesting their linguistic/pragmatic skills were not barriers to employment. Within this subgroup, however, were three individuals with ASD who have faced ongoing barriers to gaining employment. The second subgroup of ASD participants experienced moderate to severe difficulties across all tasks. No ASD participants in this subgroup were engaged in employment (full-time or otherwise). Six of the 17 ASD participants investigated in the study received speech-language intervention in childhood. Despite this, performance by four of the six ASD adults with a history of language intervention placed them in the subgroup characterised by moderate-severe difficulties in all tasks, suggesting they have considerable ongoing language needs. Mawhood et al. (2000) have argued that examining the cause of the heterogeneity within ASD may be a means of gaining insight into the disorder. The present study offers preliminary findings of a degree of heterogeneity within ASD based on verbal, but not nonverbal skills. The influence of cognitive skill on the heterogeneity of language skills has previously been examined (e.g., Szatmari et al., 1995). Contrary to Szatmari et al.’s (1995) findings, our study suggests nonverbal cognition was not a factor in the subgroup formation for the adults with ASD investigated in the study. A lack of substantial evidence of nonverbal influences in subgroup formation, however, does not suggest an absence of influence given the small number of participants involved in the subgroup analysis. The influence of cognitive performance over language performance in autism is yet to be clarified. The study has a number of limitations. The current findings were based on performance by adults with ASD on tests designed for the neurologically impaired population. There are few comprehensive linguistic and pragmatic assessments designed for adults without neurological disorders. Nonetheless, an investigation using tests designed for non-neurologically impaired

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

185

adolescents, such as the Test of Adolescent Language Third Edition (TOAL-3) (Hammill, Brown, Larsen, & Wiederholdt, 1994) may provide different results. The criteria for diagnosing the ASD participants were not known, and no validation of diagnoses was undertaken. It is, therefore possible, that the subgroups described in the current study could be the result of inaccurate diagnoses within the ASD participant group. In a similar vein, the inclusion of participants with a range of diagnoses on the autism spectrum, such as AS and HFA, may have influenced the findings, as there is ongoing debate as to whether AS and HFA are similar autistic presentations (e.g., Klin, Pauls, Schultz, & Volkmar, 2005; Klin & Volkmar, 2003; Leekam, Libby, Wing, Gould, & Gillberg, 2000; Macintosh & Dissanayake, 2004). Although the diagnostic distinction between AS and HFA is the timing of the onset of language in childhood (APA, 1994), it is currently not clear if the diagnostic distinction results in significantly different long-term outcomes for language (Howlin, 2003). Given the sample size of the study, generalising the results to the wider ASD population is not recommended. Replication of the study with a much larger sample is required. This is particularly relevant for the cluster analysis which resulted in substantially smaller sample sizes. Although nonverbal cognition was not a factor in subgroup formation, the size of the subgroups may have reduced the statistical power of the analysis. The results of the investigation of subgroups within the ASD sample should, therefore, be viewed as preliminary findings only. The present study described the linguistic and pragmatic skills of a group of adults with ASD. The influence of language on psychosocial and vocational outcomes in adults with ASD, and the relationship between cognitive skill and language skill should be the foci of future investigation. Additionally, further research is needed to determine the rate of maturation and the pattern of improvements (Seltzer et al., 2003; Tager-Flusberg, 2004) from adolescence to adulthood. Comparisons of the language profiles associated with ASD and focal brain injury may provide clinically useful data in terms of intervention strategies, if the language difficulties experienced in ASD are clinically similar to those experienced following focal neurological trauma. 4. Conclusions Previous findings may be overestimating the language skills in adults with a diagnosis of ASD. As a group, the adults with ASD in the current study presented with compromised skills in overall linguistic ability, Auditory Verbal Comprehension, naming skills, understanding non-contextual language, and using emphatic stress to convey meaning in speech. Furthermore, the group of adults with ASD did not present with homogeneous language skills. The identification of a range of linguistic and pragmatic language deficits in the adults with ASD investigated in the current study has clinical relevance. The majority of the ASD participants investigated in the present study, and all of the ASD participants in the least competent subgroup, were unemployed. A number of ASD-specific employment and training services are available (e.g., National Autistic Society, 2006), yet to offer support specific to the individual, an accurate understanding of their communicative needs is necessary. Our findings suggest that adults diagnosed with ASD should undergo a comprehensive language assessment to allow for specific assistance to be tailored to their individual needs. Work-place intervention may need to include educating employers and fellow-employees about possible language difficulties that may be impediments to successful employment for those with the diagnosis.

186

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

References Aldenderfer, M. S., & Blashfield, R. K. (1984). Cluster analysis. Beverly Hills, CA: Sage Publications. American Psychiatric Association [APA]. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington: American Psychiatric Association. Baxter, M. J. (1994). Exploratory multivariate analysis in archeology. Edinburgh: Edinburgh University Press. Booth, R., Charlton, R., Hughes, C., & Happe, F. (2003). Disentangling weak coherence and executive dysfunction: Planning drawing in autism and attention deficit/hyperactivity disorder. Philosophical Transactions of the Royal Society of London B, 358, 387–392. Brown, L., Sherbenou, R. J., & Johnsen, S. K. (1990). Test of Nonverbal Intelligence (2nd ed.). Texas: Pro-Ed. Bryan, K. L. (1989). The Right Hemisphere Language Battery. Leicester: Far communications. Clegg, J., Hollis, C., Mawhood, L., & Rutter, M. (2005). Developmental language disorders—a follow-up in later adult life. Cognitive, language and psychosocial outcomes. Journal of Child Psychology and Psychiatry, 46(2), 128–149. Dennis, M., Lazenby, A. L., & Lockyer, L. (2001). Inferential language in high-function children with autism. Journal of Autism and Developmental Disorders, 31(1), 47–54. Dunn, L., Dunn, L., Whetton, C., & Burley, J. (1997). British Picture Vocabulary Scale (revised ed.). Slough, Bucks: NFER-Nelson Publishing Co. Dunn, L., Dunn, L., Whetton, C., & Pintillie, D. (1982). British picture vocabulary scale. Slough, Bucks: NFER-Nelson Publishing Co. Eales, M. J. (1993). Pragmatic impairments in adults with childhood diagnoses of autism or developmental receptive language disorder. Journal of Autism and Developmental Disorders, 23(4), 593–617. Emerich, D. M., Creaghead, N. A., Grether, S. M., Murray, D., & Grasha, C. (2003). The comprehension of humorous materials by adolescents with high-functioning autism and Asperger’s syndrome. Journal of Autism and Developmental Disorders, 33(3), 253–257. Everitt, B. S., Landau, S., & Leese, M. (2001). Cluster analysis (4th ed.). London: Arnold. Frith, U. (2003). Autism: Explaining the enigma (2nd ed.). Oxford: Blackwell Publishing. Hammill, D. D., Brown, V. L., Larsen, S. C., & Wiederholdt, J. L. (1994). Test of Adolescent Language (3rd ed.). Austin, TX: Pro-Ed. Hill, E. L., & Frith, U. (2003). Understanding autism: Insights from mind and brain. Phil. Transactions of the Royal Society of London B, 358, 281–289. Howlin, P. (1997). Autism: Preparing for adulthood (2nd ed.). London: Routledge. Howlin, P. (2003). Outcome in high-functioning adults with autism with and without early language delays: Implications for the differentiation between autism and Asperger syndrome. Journal of Autism and Developmental Disorders, 33(1), 3–13. Howlin, P., Alcock, J., & Burkin, C. (2005). An 8 year follow-up of a specialist supported employment service for highability adults with autism or Asperger syndrome. Autism, 9(5), 533–549. Kaplan, E. F., Goodglass, H., & Weintraub, S. (1978). Boston Naming Test (exper. ed.). E. Kaplan & H. Goodglass. Kertesz, A. (1982). Western Aphasia Battery. New York: Grune and Stratton. Klin, A., Pauls, D., Schultz, R., & Volkmar, F. (2005). Three diagnostic approaches to Asperger syndrome: Implications for research. Journal of Autism and Developmental Disorders, 35(2), 221–234. Klin, A., & Volkmar, F. R. (2003). Asperger syndrome: Diagnosis and external validity. Child and Adolescent Psychiatric Clinics of North America, 12, 1–13. Koning, C., & Magill-Evans, J. (2001). Social and language skills in adolescent boys with Asperger syndrome. Autism, 5(1), 23–36. Leekam, S., Libby, S., Wing, L., Gould, J., & Gillberg, C. (2000). Comparison of ICD-10 and Gillberg’s criteria for Asperger syndrome. Autism, 4(1), 11–28. Lewis, F. M., Murdoch, B. E., & Woodyatt, G. C. Communicative competence and metalinguistic ability: Performance by children and adults with Autism Spectrum Disorder. Journal of Autism and Developmental Disorders, in press. Losh, M., & Capps, L. (2003). Narrative ability in high-functioning children with autism or Asperger’s syndrome. Journal of Autism and Developmental Disorders, 33(3), 239–251. Macintosh, K. E., & Dissanayake, C. (2004). Annotation: The similarities and differences between autistic disorder and Asperger’s disorder: A review of the empirical evidence. Journal of Child Psychology and Psychiatry, 45, 421– 434. Mawhood, L., Howlin, P., & Rutter, M. (2000). Autism and developmental receptive language disorder: A comparative follow-up in early adult life. I: Cognitive and language outcomes. Journal of Child Psychology and Psychiatry, 41(5), 547–559.

F.M. Lewis et al. / Research in Autism Spectrum Disorders 2 (2008) 176–187

187

Mayes, S. D., & Calhoun, S. L. (2001). Non-significance of early speech delay in children with autism and normal intelligence and implicatios for DSM-IV Asperger’s disorder. Autism, 5(1), 81–94. National Autistic Society (2006). Prospects. Retrieved May 9, 2006, from http://www.nas.org.uk/nas/jsp/polopoly. NCSU (2006). Cluster analysis. Retrieved November 29, 2006, from http://www2.chass.ncsu.edu/garson/PA765/ cluster.htm. Ozonoff, S., & Miller, J. N. (1996). An exploration of right-hemisphere contributions to the pragmatic impairments of autism. Brain and Language, 52, 411–434. Paul, R., Augustyn, A., Klin, A., & Volkmar, F. (2005). Perception and production of prosody by speakers with Autism Spectrum Disorders. Journal of Autism and Developmental Disorders, 35(2), 205–220. Price, I. (2000). Bonferroni adjustment. Retrieved November 29, 2006, from http://www.une.edu.au/WebStat/ unit_materials/c7_anova/oneway_bonferroni_adjust.htm. Prior, M., Leekam, S., Ong, B., Eisenmajer, R., Wing, L., Gould, J., et al. (1998). Are there subgroups within the Autistic Spectrum? A cluster analysis of a group of children with Autistic Spectrum Disorders. Journal of Child Psychology and Psychiatry, 39(6), 893–902. Rumsey, J. M. (1985). Conceptual problem-solving in highly verbal, nonretarded autistic men. Journal of Autism and Developmental Disorders, 15(1), 23–36. Rumsey, J. M., & Hamburger, S. D. (1988). Neuropsychological findings in high-functioning men with Infantile Autism, residual state. Journal of Clinical and Experimental Neuropsychology, 10(2), 210–221. Seltzer, M. M., Krauss, M. W., Shattuck, P. T., Orsmond, G., Swe, A., & Lord, C. (2003). The symptoms of Autism Spectrum Disorders in adolescence and adulthood. Journal of Autism and Developmental Disorders, 33(6), 565–581. Semel, E., Wiig, E. H., & Secord, W. (1987). Clinical Evaluation of Language Fundamentals. San Antonio, CA: Psychological Corporation. Shields, J., Varley, R., Broks, P., & Simpson, A. (1996). Hemispheric function in developmental language disorders and high-level autism. Developmental Medicine and Child Neurology, 38, 473–486. Shriberg, L. D., Paul, R., McSweeny, J. L., Klin, A., Cohen, D. J., & Volkmar, F. R. (2001). Speech and prosody characteristics of adolescents and adults with high-functioning autism and Asperger syndrome. Journal of Speech, Language, and Hearing Research, 44, 1097–1115. Sokal, R. R., & Michener, C. D. (1958). A statistical method for evaluating systematic relationships. University of Kansas Science Bulletin, 38, 1409–1438. Spreen, O., & Benton, A. L. (1969). Neurosensory Centre Comprehensive Examination for Aphasia. Victoria, Canada: University of Victoria. StatSoft, I. (1984–2004). Cluster analysis. Retrieved February 16, 2006, from http://.statsoft.com/textbook/stcluan.html. Szatmari, P., Archer, L., Fisman, S., Streiner, D. L., & Wilson, F. (1995). Asperger’s syndrome and autism: Differences in behavior, cognition, and adaptive functioning. Journal of the American Academy of Child and Adolescent Psychiatry, 34(12), 1662–1671. Tager-Flusberg, H. (2004). Strategies for conducting research on language in autism. Journal of Autism and Developmental Disorders, 34(1), 75–80. Wiig, E. H. (1989). Steps to language competence: Developing metalinguistic strategies. New York: The Psychological Association.