WHEN DOES AUTISM START?

Canadian researchers Dr. Lonnie Zwaigenbaum and Susan Bryson have enrolled 200 siblings, half of whom have been observed to the age of 2. Roughly 10 percent have been diagnosed with autism. Zwaigenbaum, of McMaster University in Ontario, says that signs of the disorder, though at first subtle, are often there from the very beginning. Preliminary data show that 6-month-olds who are later diagnosed with autism generally have good eye contact, but they're often quieter and more passive than their peers. And they may lag behind in motor developments, like sitting up or reaching for objects.

The signs often become more obvious as children reach their 1st birthdays. By then, some show patterns of extreme reactivity, either getting very upset when a new toy or activity is presented or barely noticing at all. Others already exhibit repetitive behaviors characteristic of autism--rocking back and forth or becoming fixated on an object, like a piece of string dangling in front of their eyes. And they're less responsive to playful interactions with others. When a typically developing child plays peekaboo, her face lights up, she looks at the person she's playing with, she makes sounds, she reaches for the peekaboo blanket. Children with autism, by contrast, show little facial expression. They may not look at their playmate, and it can take enormous energy to elicit a reaction. "What's been striking," says Zwaigenbaum, "is the lack of response or the distress that these activities can elicit."

The Baby Sibs consortium is also looking for early physical markers of the disorder, starting with the size of children's heads. A landmark study published in 2003 found that kids with autism experienced unusually rapid head growth between 6 and 14 months. Consortium members want to see if their young siblings do, too. Scientists aren't sure what accounts for the increase, but one theory is that it has to do with an overgrowth of neuronal connections. Normally, the brain clears out biological debris as it forms new circuits. "Little twigs fall off to leave the really strong branches," says University of Michigan researcher Catherine Lord. In kids with autism, however, that pruning process may go awry.

In their hunt for neurological clues, scientists are unveiling the inner workings of the autistic mind. Using eye-tracking technology, Ami Klin, of the Yale Child Study Center, is uncovering fascinating differences in the early socialization skills of children with autism. Klin has found that when affected toddlers view videos of caregivers or babies in a nursery, they focus more on people's mouths--or on objects behind them--than on their eyes. Klin's toddler study echoes findings in adults and adolescents with autism when they watched clips of "Who's Afraid of Virginia Woolf?" "Richard Burton and Elizabeth Taylor were engaged in a passionate kiss, and they're focusing on the light switch," says Klin. "Our goal is to identify these vulnerabilities as early as possible."

Might it be that the autistic brain's operating platform is different, as if it's a Mac in a world of PCs? Functional MRI scans show that the brain's "fusiform face area," the control tower for face recognition, is underactive in people with autism. The more severe the disorder, the more disabled the fusiform. But is it actually dysfunctional? Or is it just not interested in people? In an intriguing early study, Yale's Robert Schultz took brain scans of a child with autism who had trouble distinguishing human faces but loved the cartoon character Digimon. "Lo and behold," says Schultz, "his fusiform showed strong activity." Schultz and James Tanaka at the University of Victoria in Canada are hoping computer games can help kids with autism learn how to engage with human faces and identify emotions. The children follow directions to shoot at smiley faces or click on the guy who looks sad. In "Emotion Maker," they choose features--angry eyes, a scowling mouth--to create their own faces. And in "Who's Looking at Me?" they scan an array of faces to sensitize them to eye contact. So far, says Schultz, the kids appear to be improving. But will it help change the course of their lives? "That's the million-dollar question," he says.

An intellectual thief, autism infiltrates children's brains, stalling or stealing cognitive and social development. In classic autism, babies fail to coo or babble by their 1st birthdays. Or words that do develop ("dada," "up," "toy") inexplicably disappear. One-year-olds don't respond to their names. A child once bursting with potential finds spinning tops more captivating than her mother's smile. Kids with Asperger's may not be as closed off, but they suffer severe social deficits. Many are verbal fanatics, immersing themselves in long-winded monologues about obscure topics, like fat fryers or snakes. Klin recalls a child who bowed and spoke in Shakespearean English, "almost as if I had plucked him from 14th-century Verona." Such oddities can make these children social pariahs. Baffled by human interactions and frustrated by their inability to make friends, some kids spiral into debilitating fits of anxiety and depression. Many children on the autism spectrum will never live independent lives. "We're talking about children who need lifelong care," says NIMH's Insel. "This is an astonishingly devastating disease."