The level and nature of autistic intelligence

Abstract

Autistics are presumed to be characterized by cognitive impairment, and their cognitive strengths (e.g., in Block Design performance) are frequently interpreted as low-level by-products of high-level deficits, not as direct manifestations of intelligence. Recent attempts to identify the neuroanatomical and neurofunctional signature of autism have been positioned on this universal, but untested, assumption. We therefore assessed a broad sample of 38 autistic children on the preeminent test of fluid intelligence, Raven's Progressive Matrices. Their scores were, on average, 30 percentile points, and in some cases more than 70 percentile points, higher than their scores on the Wechsler scales of intelligence. Typically developing control children showed no such discrepancy, and a similar contrast was observed when a sample of autistic adults was compared with a sample of nonautistic adults. We conclude that intelligence has been underestimated in autistics.

Fig. 1

Mean subtest scores of the 38 autistic children on the Wechsler Intelligence Scale for Children–Third Edition.

Fig. 2

Performance of the (a) autistic and nonautistic children and (b) autistic and nonautistic adults on the Wechsler scales and Raven’s Progressive Matrices. Error bars represent 2 SEMs. WAIS-III = Wechsler Adult Intelligence Scale–Third Edition; WISC-III = Wechsler Intelligence Scale for Children–Third Edition.

Fig. 3

Relation between Full Scale IQ on the Wechsler Intelligence Scale for Children–Third Edition (WISC-III) and Raven’s Progressive Matrices scores in (a) autistic children and (b) control children. Data points to the left of the dashed diagonal lines represent subjects whose Raven’s Matrices scores were greater than their WISC-III scores; data points to the left of the solid diagonal lines represent subjects whose Raven’s Matrices scores were 50 percentile points greater than their WISC-III scores. In (a), a circle surrounds the data points for 7 autistic children whose Raven’s Matrices scores exceeded their WISC-III scores by more than 70 percentile points. Diamonds represent identical data points from 2 subjects.