In 1981, however, British psychiatrist Dr. Lorna Wing published an influential paper that revived interest in Asperger's work. The disorder Asperger identified, Wing observed, appeared in many ways to be a variant of Kanner's autism, so that the commonalities seemed as important as the differences. As a result, researchers now believe that Asperger and Kanner were describing two faces of a highly complicated and variable disorder, one that has its source in the kaleidoscope of traits encoded in the human genome. Researchers also recognize that severe autism is not always accompanied by compensatory intellectual gifts and is, in fact, far likelier to be characterized by heartbreaking deficits and mental retardation.

Perhaps the most provocative finding scientists have made to date is that the components of autism, far more than autism itself, tend to run in families. Thus even though profoundly autistic people rarely have children, researchers often find that a close relative is affected by some aspect of the disorder. A sister may engage in odd repetitive behavior or be excessively shy; a brother may have difficulties with language or be socially inept to a noticeable degree. In similar fashion, if one identical twin has autism, there is a 60% chance that the other will too and a better than 75% chance that the twin without autism will exhibit one or more autistic traits.

How many genes contribute to susceptibility to autism? Present estimates run from as few as three to more than 20. Coming under intensifying scrutiny, as the papers published by Molecular Psychiatry indicate, are genes that regulate the action of three powerful neurotransmitters: glutamate, which is intimately involved in learning and memory, and serotonin and gamma-aminobutiric acid (gaba), which have been implicated in obsessive-compulsive behavior, anxiety and depression.

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."

At the same time, it is incorrect to say autistic people are cold and indifferent to those around them or, as conventional wisdom once had it, lack the high-level trait known as empathy. Last December, when Pam Barrett felt overwhelmed and dissolved into tears, it was Danny, the most deeply autistic of her children, who rushed to her side and rocked her back and forth in his arms.

Another misperception about people with autism, says Karen Pierce, a neuroscientist at the University of California at San Diego, is the notion that they do not register faces of loved ones as special — that, in the words of a prominent brain expert, they view their own mother's face as the equivalent of a paper cup. Quite the contrary, says Pierce, who has results from a neuroimaging study to back up her contention. Moreover, the center of activity in the autistic mind, she reported at a conference held in San Diego last November, turns out to be the fusiform gyrus, an area of the brain that in normal people specializes in the recognition of human faces.

In a neuroimaging study, Pierce observed, the fusiform gyrus in autistic people did not react when they were presented with photographs of strangers, but when photographs of parents were substituted, the area lit up like an explosion of Roman candles. Furthermore, this burst of activity was not confined to the fusiform gyrus but, as in normal subjects, extended into areas of the brain that respond to emotionally loaded events. To Pierce, this suggests that as babies, autistic people are able to form strong emotional attachments, so their social aloofness later on appears to be the consequence of a brain disorganization that worsens as development continues.

In so many ways, study after study has found, autistic people do not parse information as others do. University of Illinois psychologist John Sweeney, for example, has found that activity in the prefrontal and parietal cortex is far below normal in autistic adults asked to perform a simple task involving spatial memory. These areas of the brain, he notes, are essential to planning and problem solving, and among their jobs is keeping a dynamically changing spatial map in a cache of working memory. As Sweeney sees it, the poor performance of his autistic subjects of the task he set for them — keeping tabs on the location of a blinking light — suggests that they may have trouble updating that cache or accessing it in real time.

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