Because “geek” is not the most scientific term, and for some may be pejorative, I needed to formulate a more precise definition of the cognitive talents shared by technical-minded people and people with autism. In the early 2000s Wheelwright and I surveyed nearly 100 families with at least one child with autism and asked another basic question: What was their child's obsession? We received a diverse array of answers that included memorizing train timetables, learning the names of every member of a category (for instance, dinosaurs, cars, mushrooms), putting electrical switches around the house into particular positions, and running the water in the sink and rushing outside to see it flowing out of the drainpipe.
On the surface, these very different behaviors seem to share little, but they are all examples of systemizing. I define systemizing as the drive to analyze or construct a system—a mechanical system (such as a car or computer), a natural system (nutrition) or an abstract system (mathematics). Systemizing is not restricted to technology, engineering and math. Some systems are even social, such as a business, and some involve artistic pursuits, such as classical dance or piano. All systems follow rules. When you systemize, you identify the rules that govern the system so you can predict how that system works. This fundamental drive to systemize might explain why people with autism love repetition and resist unexpected changes.
Collaborating once again with Wheelwright, who is now at the University of Southampton in England, I put the link between systemizing and autism to the test. We found that children with Asperger's syndrome—a form of autism with no language or intelligence impairments—outperformed older, typically developing children on a test of understanding mechanics. We also found that on average, adults and children with Asperger's scored higher on self-report and parent-report measures of systemizing. Finally, we found that people with Asperger's scored higher on a test of attention to detail. Attention to detail is a prerequisite for good systemizing. It makes a world of difference when trying to understand a system if you spot the small details or if you mistake one tiny variable in the system. (Imagine getting one digit wrong in a math calculation.) When we gave the test of attention to detail to parents, both the mothers and fathers of children with autism were also faster and more accurate than those of typically developing children.
Engineers aren't the only technical-minded people who might harbor autism genes. In 1998 Wheelwright and I found that math students at the University of Cambridge were nine times more likely than humanities students to report having a formal diagnosis of autism, including Asperger's, which will be folded into the broader “autism spectrum disorder” in the newest edition of psychiatry's guidebook, the DSM-5. Whereas only 0.2 percent of students in the humanities had autism, a figure not so different from the rate of autism reported in the wider population at the time, 1.8 percent of the math students had it. We also found that the siblings of mathematicians were five times more likely to have autism, compared with the siblings of those in the humanities.
In another test of the link between autism and math, Wheelwright and I developed a metric for measuring traits associated with autism in the general population, called the Autism Spectrum Quotient (AQ). It has 50 items, each representing one such trait. No one scores zero on the test. On average, typically developing men score 17 out of 50, and typically developing women score 15 out of 50. People with autism usually score above 32. We gave the AQ to winners of the British Mathematical Olympiad. They averaged 21 out of 50. This pattern suggested that—regardless of official diagnoses—mathematical talent was also linked to a higher number of traits associated with autism.