“There’s a tremendous concentration of autism-related syndrome in the computer industry, and I get a lot of hits on my Web site from those companies,” says Temple Grandin, professor of animal science at Colorado State University, in Fort Collins, and perhaps the most famous autistic person alive. She designed a widely used humane cattle-slaughtering system; wrote an intellectual memoir, Thinking in Pictures (Doubleday, 1995); and now devotes much of her time to the causes and human effects of autism.

“Genetics are probably 80 percent of it,” Grandin says, “but I think there must be something in the environment that’s causing the most severe kind of autism, in kids of two and three years who start out fine but then show regression in language skills. Is it vaccines? That’s the $64 000 question.”

Baron-Cohen posits that people fall into eight categories of systemizing. Those in the first category give little attention to law-governed patterns; those in the eighth give attention to little else. A level-eight autistic person can spend all day staring at the blades of a rotating fan and will either ignore or retreat in horror from any change in a stereotyped routine.

So intently do those with autism focus on the trees that they often cannot see the forest. “What happens if you have such an extreme systemizing style that you study a rotating wheel close to your eye, looking at the tiny details, not playing with it as a typical child does,” says Baron-Cohen. “Your systemizing is so extreme that you learn everything there is to know of that wheel, but a psychologist giving you a test would find a learning disability.”

With high-functioning autistic people—those who tend to fall into categories six and seven—a slightly weaker systemizing tendency allows them to tolerate irregularity enough to cope with the world. They can master self-contained bodies of knowledge, such as calendar calculation, or the ability to name the day of the week on which a date centuries into the past or future falls. This trick is commonly found in savants, such as the character played by Dustin Hoffman in the movie Rain Man.

At a lower level of systemizing are people with Asperger’s syndrome, who often have intelligence that is above average, even extraordinarily so. Although they, too, cannot easily grasp social situations, they can often compensate through the sheer application of logical analysis, a method that Baron-Cohen calls “hacking the social system.”

Some psychologists wonder whether Asperger’s should be considered a disorder at all, given that many who “suffer” from it have made such extraordinary contributions in their fields. One such person whom Baron-Cohen has examined is Richard E. Borcherds, a Briton who won a 1998 Fields Medal, the preeminent honor in mathematics; intriguingly, he has a brother who has been diagnosed with autism. Another person with Asperger’s, it is thought, may have been Isaac Newton who, after losing a great sum of money in the South Sea Bubble financial scandal, famously remarked, “I can calculate the motion of heavenly bodies but not the madness of crowds.” Still another possibility was Albert Einstein, a lifelong loner who did not become fully fluent in language until late childhood.

Systemizers of a less extreme stamp—categories three and four in Baron-Cohen’s model—flourish in engineering, programming, the physical sciences, and accounting. Mathematicians are the most systemizing of all, scoring highest, on average, on the Autism Spectrum Screening Questionnaire [to participate, go to http://www.cambridgepsychology.com/parents]. The siblings and children of people in all these professions tend to score highly as well.

In Baron-Cohen’s model, the bimodal distribution of mental styles places most people either a bit to the left or to the right of the center, unlike the familiar Gaussian bell curve, where the majority cluster in the middle. “We see very few people who are ‘balanced,’ as there is an advantage to specialization,” Baron-Cohen says. “Think in evolutionary terms: by specializing for empathy, say, you could find networking and socializing very easy—that would become your area of strength—and you wouldn’t be distracted by searching for tiny patterns in the environment.” He places himself in the empathy category, by the way.

The bimodality originates in sex differences, and because men are more likely than women to be systemizers—as well as autistic—Bar-Cohen has characterized autism as embodying “the extreme male mind.” That is, he views it not as an isolated problem but as a point on a smoothly varying continuum.

He and his colleagues have administered tests to a representative sample of the population and found that the chance of being a systemizer is 44 percent in men and 14 percent in women. The product of the two probabilities is 7 percent, “remarkably close to the actual rate of autism spectrum conditions in the general population,” Baron-Cohen wrote in a paper published online in March in Progress in Neuro-Psychopharmacology & Biological Psychiatry.

What could cause the sex difference? Not genes alone, probably, if only because the sexes differ genetically on just one of 46 chromosomes. It is more likely that the presence of male hormones accentuates the action of the genes that predispose a brain to develop the systemizing tendency. There is some confirmation for this hypothesis in reports that systemizing tendencies may be stronger in women who were exposed in utero to high levels of male hormones.

One thing is clear: both the fathers and the mothers of children with autism themselves score above the average on the autism questionnaire and on other measures of the systemizing tendency.

Perhaps we must accept certain psychological extremes as inevitable side effects of essentially beneficial genes. “If we were to get rid of the autism genetics, we’d have no science,” Grandin says. “We’d have a lot of talented people but nobody who could make things.” And maybe this publication wouldn’t have many readers.