[Thanks to Marco G for proofreading and offering suggestions]

I.

Several studies have shown a genetic link between autism and intelligence; genes that contribute to autism risk also contribute to high IQ. But studies show autistic people generally have lower intelligence than neurotypical controls, often much lower. What is going on?

First, the studies. This study from UK Biobank finds a genetic correlation between genetic risk for autism and educational attainment (r = 0.34), and between autism and verbal-numerical reasoning (r = 0.19). This study of three large birth cohorts finds a correlation between genetic risk for autism and cognitive ability (beta = 0.07). This study of 45,000 Danes finds that genetic risk for autism correlates at about 0.2 with both IQ and educational attainment. These are just three randomly-selected...