The level and nature of autistic intelligence II: what about Asperger syndrome?

Abstract

A distinctively uneven profile of intelligence is a feature of the autistic spectrum. Within the spectrum, Asperger individuals differ from autistics in their early speech development and in being less likely to be characterized by visuospatial peaks. While different specific strengths characterize different autistic spectrum subgroups, all such peaks of ability have been interpreted as deficits: isolated, aberrant, and irreconcilable with real human intelligence. This view has recently been challenged by findings of autistic strengths in performance on Raven's Progressive Matrices (RPM), an important marker of general and fluid intelligence. We investigated whether these findings extend to Asperger syndrome, an autistic spectrum subgroup characterized by verbal peaks of ability, and whether the cognitive mechanisms underlying autistic and Asperger RPM performance differ. Thirty-two Asperger adults displayed a significant advantage on RPM over Wechsler Full-Scale and Performance scores relative to their typical controls, while in 25 Asperger children an RPM advantage was found over Wechsler Performance scores only. As previously found with autistics, Asperger children and adults achieved RPM scores at a level reflecting their Wechsler peaks of ability. Therefore, strengths in RPM performance span the autistic spectrum and imply a common mechanism advantageously applied to different facets of cognition. Autistic spectrum intelligence is atypical, but also genuine, general, and underestimated.

Figure 1. Performance on the Wechsler Intelligence Scales and Raven's Progressive Matrices by autistic and non-autistic adults (A) and children (B).

Adapted from Dawson et al., 2007.

Figure 2. Wechsler subtest profile in Asperger adults and children.

Asperger adults are shown in blue and Asperger children in red. INF: Information. SIM: Similarities. ARI: Arithmetic. VOC: Vocabulary. COM: Comprehension. PC: Picture completion. COD: Digit symbol-Coding. PA: Picture arrangement. BD: Block Design. MA: Matrix Reasoning.

Figure 3. Performance on the Wechsler Intelligence Scales and Raven's Progressive Matrices.

Performance on the Wechsler Intelligence Scales (blue) and Raven's Progressive Matrices (red) is shown for A) Asperger adults and non-Asperger adults, and B) Asperger children and non-Asperger children. FSIQ: Full-Scale IQ. VIQ: Verbal IQ. PIQ: Performance IQ.