Sex differences in autism.
Among autistic preschool and early-elementary kids, boys post higher nonverbal IQ and visual-motor scores than girls, but the gap shrinks once overall cognitive level is taken into account.
01Research in Context
What this study did
Catania et al. (1982) looked at autistic boys and girls in preschool and early elementary years. They gave each child tests for eye-hand skills, perception, and nonverbal IQ.
The team wanted to see if boys and girls with autism scored differently on these tasks.
What they found
Boys outscored girls on all three measures. The gap was biggest on nonverbal IQ.
When the researchers held nonverbal IQ steady, most sex differences faded. This hints that overall thinking level, not sex itself, drives the score gap.
How this fits with other research
Banach et al. (2009) conceptually replicated the sex-IQ link but added a twist. In simplex families, girls again scored lower than boys, yet in multiplex families the gap vanished. Family type, not just sex, shapes the numbers.
Billings et al. (1985) extended the same lens to prevalence. They showed autistic girls are over-represented only in the lowest IQ band (<34). Together, the three papers form a thread: girls with autism are more likely to appear when both autism and very low nonverbal IQ are present.
Panahi et al. (2023) move from cognition to biology. They found boys have shorter telomeres than girls with autism, giving a possible biological marker that parallels the cognitive sex split.
Why it matters
When you test a young girl for autism, expect her nonverbal scores to look lower than boys in your sample. Before you flag this as a true sex deficit, check her overall cognitive level. If it is low, her profile may reflect that, not a separate female phenotype. Use the same IQ control in your reports and keep an eye on family type—simplex versus multiplex—when you interpret scores.
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02At a glance
03Original abstract
Comparisons were made between male and female children with autism, 384 boys and 91 girls, aged 3 years to 8 years, on nonverbal measures of intelligence, adaptive functioning, receptive vocabulary, perception, and eye-hand integration, and on ratings of affect, play, and relating and human interest. Males showed more advanced performances on eye-hand integration and perception skills on the Psychoeducational Profile (PEP) and had higher nonverbal IQs social quotients, and Peabody Picture Vocabulary Test (PPVT) IQs than females. When nonverbal IQ was controlled, the main effect of sex remained; however, sex differences on PPVT scores and on eye-hand integration and perception scale disappeared. Males showed more unusual visual responses and less appropriate, more stereotypic play than females. These results are discussed in terms of hypotheses concerning sex differences in genetic thresholds and in hemispheric lateralization.
Journal of autism and developmental disorders, 1982 · doi:10.1007/BF01538320