Adam hadn't wanted to see his father for the two years prior, it made we wonder if Peter wasn't giving off a vibe that he wished Adam had never been born

I wondered how Peter would feel if he could see his son again. "Quite honestly, I think that I wouldn't recognize the person I saw," he said. "All I could picture is there'd be nothing there, there'd be nothing. Almost, like, `Who are you, stranger?' " Peter declared that he wished Adam had never been born, that there could be no remembering who he was outside of who he became. "That didn't come right away. That's not a natural thing, when you're thinking about your kid. But, God, there's no question. There can only be one conclusion, when you finally get there. That's fairly recent, too, but that's totally where I am."

"Adam was not open to therapy," Peter told me. "He did not want to talk about problems and didn't even admit he had Asperger's." Peter and Nancy were confident enough in the Asperger's diagnosis that they didn't look for other explanations for Adam's behavior. In that sense, Asperger's may have distracted them from whatever else was amiss. "If he had been a totally normal adolescent and he was well adjusted and then all of a sudden went into isolation, alarms would go off," Peter told me. "But let's keep in mind that you expect Adam to be weird." Still, Peter and Nancy sought professional support repeatedly, and none of the doctors they saw detected troubling violence in Adam's disposition. According to the state's attorney's report, "Those mental health professionals who saw him did not see anything that would have predicted his future behavior." Peter said, "Here we are near New York, one of the best locations for mental-health care, and nobody saw this."

Peter gets annoyed when people speculate that Asperger's was the cause of Adam's rampage. "Asperger's makes people unusual, but it doesn't make people like this," he said, and expressed the view that the condition "veiled a contaminant" that was not Asperger's: "I was thinking it could mask schizophrenia." Violence by autistic people is more commonly reactive than planned--triggered, for example, by an invasion of personal space. Studies of people with autism who have committed crimes suggest that at least half also suffer from an additional condition--from psychosis, in about twenty-five per cent of cases. Some researchers believe that a marked increase in the intensity of an autistic person's preoccupations can be a warning sign, especially if those preoccupations have a sinister aspect. Forensic records of Adam's online activity show that, in his late teens, he developed a preoccupation with mass murder. But there was never a warning sign; his obsession was discussed only pseudonymously with others online.

Both autism and psychopathy entail a lack of empathy. Psychologists, though, distinguish between the "cognitive empathy" deficits of autism (difficulty understanding what emotions are, trouble interpreting other people's nonverbal signs) and the "emotional empathy" deficits of psychopathy (lack of concern about hurting other people, an inability to share their feelings). The subgroup of people with neither kind of empathy appears to be small, but such people may act out their malice in ways that can feel both guileless and brutal.

Autism is increasingly invoked in courtrooms as an argument for leniency, sometimes on the ground that the autistic person is confused about cause and effect--a befuddlement defense, as it were. Adam Lanza, however, clearly understood what he was doing. He destroyed one of his hard drives, and left behind an electronic spreadsheet on mass murder, and photographs of himself with a gun to his head. A recent study suggests that a lack of empathy may be connected to insensitivity to physical pain. Despite Adam's hypersensitivity to more minor irritants, this seems to have been one of his symptoms; his mother warned the school that he might not stop doing something because it hurt.

Geneticists are starting to pinpoint the DNA anomalies found in kids like Matt who are savants from birth. Still, a single savant gene will probably never be found. More than a dozen genes may contribute to autism. Several other forms of mental impairment also produce islands of startling ability - known as splinter skills - as if fragments of savant code are scattered throughout the genetic database.

Last year, researchers at Vanderbilt University discovered a cluster of abnormalities on chromosome 15 in the families of autistic savants. Another set of irregularities on the same chromosome produces learning-disabled kids who can solve jigsaw puzzles twice as fast as other children and have an insatiable desire to overeat - Prader-Willi syndrome. A third chromosomal disorder, called Williams syndrome, results in mental retardation, poor coordination, and a different set of splinter skills. Williams kids, who have distinctively elfin facial features, are naturally outgoing, love to schmooze, and have a propensity for florid verbal constructions (hyperlexia), similar to Matt's discourse on proportions.

Like savants, people with Williams syndrome have an unusual relationship with the audible world. Some are terrified as children by the hum of household appliances, but others become connoisseurs of the rich drones of machines, like a boy described in the clinical literature who had a collection of 18 different vacuum cleaners. Many people with Williams also excel at picking out the notes in a chord. Some are so sensitive that they can identify the make and model of a car from the sound of its engine.

In tests conducted at a music camp in Massachusetts, psychologists found that the errors made by Williams kids were more musical than those made by a control group. On a clapping test, those in the control group sometimes just dropped the beat, but the Williams kids made mistakes that elaborated on the rhythms. They were jamming.

In the same way that Matt's mind is made of math problems, the minds of Williams syndrome kids are made of sound. As one girl told a researcher, "Music is my favorite way of thinking."

Wired