Gender-Specific Differences in Autism Spectrum Cognitive Profiles: Wechsler Intelligence Scales Versus Raven's Progressive Matrices

Background:   Differences in prevalence rates suggest gender distinctions within the autism spectrum, as may cognitive profiles. Typically, versions of the Wechsler intelligence scales (WIS), with both verbal (VIQ) and performance (PIQ) subtests, have been used as a measure of autistic cognitive ability. Existing findings include that although autistic males and females share similar cognitive profiles for VIQ subtests, females perform better on the PIQ subtests Coding and Symbol Search, but significantly worse on the Block Design subtest, compared to males (Koyama et al., 2009). However, the reliability of IQ assessment of autistic intelligence using WIS has been challenged, including because VIQ subtests require typical speech comprehension and production abilities. In contrast, Raven’s Progressive Matrices (RPM), an important test of fluid and general intelligence, minimizes such requirements and thus may better estimate autistic intelligence (e.g., Dawson, et al., 2007). However, there is the possibility that male and female autistics differ in their profile of WIS versus RPM performance.

Objectives:   We aimed to assess whether gender-related differences in cognitive profiles in the autism spectrum depend on the type of assessment instrument used, by testing whether WIS and RPM are equivalent measures of cognitive abilities in autism spectrum females.

Methods:   Cognitive profiles were drawn from the databases of two University-affiliated autism clinics in Montreal.  Participants met criteria for either the specific diagnosis of autism (AUT) or Asperger syndrome (ASP) according to DSM-IV-TR criteria. All participants were aged 20 years or older at assessment and were thus tested on the Wechsler Adult Intelligence Scale, 3^rdedition (WAIS-III) as well as RPM. WIS and RPM-based cognitive profiles of 21 females (12 AUT, 9 ASP) were compared to those of 54 males (24 AUT, 30 ASP). Full-scale (FSIQ), PIQ, and VIQ, as well as raw RPM scores were averaged across AUT and ASP subgroups; mean scores for core subtests were also obtained.

Results:   WIS scores were significantly higher for autism spectrum males than for females on Wechsler FSIQ (p=0.02) and VIQ (p=0.03) but not for PIQ (p=0.79). Gender-contingent differences on some WIS subtests were also found, with autism spectrum males outperforming females on Arithmetic (p<0.01) and Matrix Reasoning (p=0.05) subtests. When controlling for age at assessment, ANCOVAs revealed that Gender differences were not found for RPM performance (p=0.85).

Conclusions:   Comparing WIS and RPM performance in autism spectrum males versus females provides preliminary insight into possible gender distinctions in cognitive profiles in this population. Such distinctions may be important for interpreting research findings and in clinical decisions about how best to assess autistic abilities. We are presently assessing whether similar instrument-specific gender differences are manifested in children and adolescents on the autism spectrum.