This research extends previous research regarding the intellectual functioning of autistic individuals on standardized measures of intelligence (Wechsler Adult Intelligence Scale-Revised and the Wechsler Intelligence Scale for Children-Revised). In Study I 33 individuals with autism who closely fit the DSM-III criteria were studied. Clear evidence was found that differentiates these individuals' verbal intellectual processes from their visual-motor intellectual abilities. Principal components analysis was used to examine the interrelationship among the various intellectual abilities which such tests of intelligence measure. In Study II the intellectual abilities of a group of autistic 8- to 12-year-olds were compared to age-matched groups of children with receptive developmental language disorder, dysthymic disorder, or oppositional disorder. The intellectual abilities of autistic children were significantly different from the other groups of children.

Event-related brain potentials (ERPs) elicited by visual and auditory stimuli were recorded from nonretarded individuals with autism (ages 13-25 years) and age-matched normal controls. In "no-task" conditions, subjects simply looked at or listened to these stimuli; only one difference was found between subject groups. Several ERP differences between groups were found in "task" conditions; subjects pressed a button at the occurrence of target stimuli intermixed with unexpected, novel stimuli and also with expected, nonnovel stimuli. Visual ERP abnormalities in the autistic group differed from auditory abnormalities. Results suggest that (1) nonretarded autistic individuals may have a limited capacity to process novel information--they are neither hypersensitive to novel information nor misperceive it as nonnovel and insignificant; (2) classification of simple visual information may be less impaired than auditory; and (3) with one exception, visual and auditory ERP abnormalities do not seem to reflect maturational delay.

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A number of studies comparing the Wechsler-Bellevue (W-B) and the Wechsler Intelligence Scale for Children (WISC) with the Stanford-Binet (S-B) have been reported. Correlation coefficients between IQs from these Wechsler scales and the S-B have been of the same order (.6 to .9) in normal, neuropsychiatric, and mentally retarded populations (

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