The Emergence of Distinct Patterns of Nonverbal Cognitive Abilities in Preschoolers with Autism

Background:  

Uneven patterns of cognitive abilities have been documented among individuals with autism suggesting enhanced nonverbal abilities over verbal abilities.  However, among superior performance on tests of nonverbal abilities, there exists variability in performance in individuals with autism.  Research has suggested that individuals with autism show enhanced perceptual or visuospatial abilities and weaker conceptual or abstraction abilities within the non-verbal domain. This study aimed to prospectively examine the development of these patterns of nonverbal cognitive processing over time in younger children with ASD.  This is an important step in further uncovering the development of unique cognitive profiles in young children with autism.

Objectives:  

To examine a proposed pattern of relative strengths in perceptual nonverbal cognitive abilities and relative weaknesses in conceptual nonverbal abilities over time within the cognitive profiles of children with autism.

Methods:  

Participants consisted of a clinically referred sample of 27 children (n= 21 [75%] male) with an ASD diagnosis based on the Autism Diagnostic Observation Schedule and clinical impression (Autism n= 13; PDD-NOS n= 14).  All data were collected during a comprehensive clinical diagnostic evaluation at a special education preschool.  Nonverbal cognitive abilities were estimated using the Leiter International Performance Scale–Revised (Leiter-R) Brief IQ Screener [Figure Ground (FG), Form Completion (FC), Repeated Patterns (RP), and Sequential Order (SO)] at two time points (mean age=41.7 months and mean age=59.7 months).  A relative strength on subtests that depend on perceptual processes (i.e., FG and FC) compared to relative weaknesses in the subtests that require abstract reasoning or concept formulation (i.e., RP and SO) would represent the proposed pattern of strengths and weaknesses in non-verbal cognitive processing consistent with finding from Kuschner and colleagues (2007).  This study aims to replicate these previous findings as well as examine when this pattern emerges over time. 

Results:  

Paired samples t-tests at Time 1 indicate no differences (all ps> .50) among the Brief IQ subtests.  Paired samples t-tests at Time 2 indicate differences between FC>FG=RP>SO (ps< .05); however, differences between FG-RP were not found (p>.76).  Ipsative subtest profiles were also constructed relative to each child’s overall performance.  Four paired sample t tests were performed comparing Time 1 deviation scores to Time 2 deviation scores for each Brief IQ subtest.  Findings suggest differences between FC1<FC2 and SO1>SO2 (ps<.05); however differences between FG1-FG2 and RP1-RP2 were not found (ps>.72).  

Conclusions:  

At Time 1, we find that young preschoolers with autism are not showing specific strengths and weaknesses within their cognitive profile, suggesting flat profiles of comparable nonverbal abilities.  In contrast, at Time 2 (18 months later), children with autism are showing relative strengths on FC and relative weaknesses on SO.  Findings suggest that an uneven pattern of relative strengths and weaknesses in cognition found in previous research on individuals with autism, namely strengths in nonverbal perceptual versus nonverbal conceptual skills are evident for older preschoolers (on specific Leiter-R subtests), but not present for younger preschoolers with autism.  This unique profile may have implications for intervention.