Brief Report: Relationship between non-verbal IQ and gender in autism.
Girls with autism score lower on non-verbal IQ than boys only in simplex families, so family structure changes how we interpret their scores.
01Research in Context
What this study did
Banach et al. (2009) looked at non-verbal IQ scores in kids with autism.
They split the families into two groups: simplex (one child with autism) and multiplex (more than one child with autism).
Then they checked if boys and girls scored differently on the same non-verbal IQ test.
What they found
In simplex families, girls with autism had lower non-verbal IQ scores than boys.
In multiplex families, the scores were the same for both sexes.
Family type, not just sex, shaped the IQ gap.
How this fits with other research
Billings et al. (1985) first noticed that autistic girls cluster at the lowest IQ levels. Ryan’s team shows the same girl-boy gap, but only in simplex homes.
Catania et al. (1982) also found autistic boys scoring higher on non-verbal IQ. Ryan refines this by showing the gap vanishes in multiplex homes, hinting that different genes are at work.
Allen et al. (2001) found birth-order IQ gaps inside multiplex homes. Ryan adds a sex angle, proving multiplex families can hide other patterns that pop out in simplex ones.
Why it matters
When you test IQ, note family type. A low non-verbal score in a girl from a simplex family may reflect a stronger genetic hit, not just overall ability. This can guide you toward different teaching speeds, more visual supports, or earlier AAC trials for these girls.
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02At a glance
03Original abstract
It has been proposed that females at risk for autism are protected in some way, so that only those with the greatest genetic liability are affected. Consequently, affected male siblings of females with autism should be more impaired than affected male siblings of male probands. One hundred and ninety-four (194) families with a single child with autism (simplex, SPX) and 154 families with more than one child with autism (multiplex, MPX) were examined on measures of severity, including non-verbal IQ. Among SPX families, girls had lower IQ than boys, but no such differences were seen among MPX families. Similarly, the affected brothers of girls with autism were no different from affected brothers of male probands. These data suggest that MPX and SPX families differ with respect to the relationship between gender and IQ.
Journal of autism and developmental disorders, 2009 · doi:10.1007/s10803-008-0612-4