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Those genes hardly exhaust the list of possibilities. Among the suspects are virtually all the genes that control brain development and perhaps cholesterol and immune-system function as well. Christopher Stodgell, a developmental toxicologist at New York's University of Rochester, observes that the process that sets up the brain resembles an amazingly intricate musical score, and there are tens of thousands of genes in the orchestra. If these genes do what they're supposed to do, says Stodgell, "then you have a Mozart's Concerto for Clarinet. If not, you have cacophony."
A DIFFERENCE OF MIND
Autistic people often suffer from a bewildering array of problems--sensory disturbances, food allergies, gastrointestinal problems, depression, obsessive compulsiveness, subclinical epilepsy, attention-deficit hyperactivity disorder. But there is, researchers believe, a central defect, and that is the difficulty people across the autistic spectrum have in developing a theory of mind. That's psychologese for the realization, which most children come to by the age of 4, that other people have thoughts, wishes and desires that are not mirror images of their own. As University of Washington child psychologist Andrew Meltzoff sees it, the developmental stage known as the terrible twos occurs because children--normal children, anyway--make the hypothesis that their parents have independent minds and then, like proper scientists, set out to test it.
Children on the autistic spectrum, however, are "mind blind"; they appear to think that what is in their mind is identical to what is in everyone else's mind and that how they feel is how everyone else feels. The notion that other people--parents, playmates, teachers--may take a different view of things, that they may harbor concealed motives or duplicitous thoughts, does not readily occur. "It took the longest time for Tommy to tell a lie," recalls Pam Barrett, and when he finally did, she inwardly cheered.
Meltzoff believes that this lack can be traced to the problem that autistic children have in imitating the adults in their lives. If an adult sits down with a normal 18-month-old and engages in some interesting behavior--pounding a pair of blocks on the floor, perhaps, or making faces--the child usually responds by doing the same. Young children with autism, however, do not, as Meltzoff and his colleague Geraldine Dawson have shown in a series of playroom experiments.
The consequences of this failure can be serious. In the early years of life, imitation is one of a child's most powerful tools for learning. It is through imitation that children learn to mouth their first words and master the rich nonverbal language of body posture and facial expression. In this way, Meltzoff says, children learn that drooping shoulders equal sadness or physical exhaustion and that twinkling eyes mean happiness or perhaps mischievousness.
For autistic people--even high-functioning autistic people--the ability to read the internal state of another person comes only after long struggle, and even then most of them fail to detect the subtle signals that normal individuals unconsciously broadcast. "I had no idea that other people communicated through subtle eye movements," says autistic engineer Temple Grandin, "until I read it in a magazine five years ago" (see box).