Increasing evidence from neuroscience suggests that many aspects of antisocial behavior can be traced to dysfunctional brains. For instance, brain scans of prisoners suggest the circuitry involved in fear conditioning has gone awry in criminal minds. Deformities of certain parts of the brain that may contribute to antisocial and psychopathic behavior have also been linked to a greater risk of arrests and convictions. For a definitive answer, scientists would have to scan the brains of thousands of children, then check back decades later to see which ones went on to lead lives of crime. If the immature brains of the future criminals were different from the immature brains of law-abiding citizens, it would be a powerful piece of evidence that some people are biologically predisposed to criminal activity, according to a group of researchers from the University of Pennsylvania, the University of Southern California, and the University of York in England. That experiment is too ambitious, but the researchers did something similar. In the early 1970s, they traveled to the island nation of Mauritius, off the eastern coast of Africa. They recruited 1,795 3-year-olds and gave them a test designed to measure whether their amygdalae -- the part of the brain involved in processing fear -- were developing normally. The test involved a series of 12 tones. Some of them were pleasant. Others were higher-pitched and were followed by a jarring sound produced by 'jangling metal objects,' according to a report in The American Journal of Psychiatry. The children were hooked up to a polygraph to measure their reactions to the noises. The high-pitched tones were supposed to make them sweat in anticipation of the unpleasant sound, while the pleasant tones weren't supposed to elicit much response. Twenty years later, the researchers scoured court records to see whether any of their subjects had committed crimes involving violence, drugs, property or serious driving offenses. (Parking fines, expired car registrations and other petty crimes weren't counted.) It turned out that 137 of the subjects -- nearly 8 percent of the total -- had criminal records. Looking back at their childhood tests, the scientists found that their reactions to the pleasant and high-pitched tones were the same. That was in stark contrast to the other subjects, who learned to fear the high-pitched tones and sweated accordingly. For the comparisons, criminals were matched with two non-offenders of the same age, gender, ethnicity and socioeconomic status. The results suggest that criminal behavior may be hard-wired -- to some degree -- in children as young as 3 and could be the result of a malfunctioning amygdala, the researchers wrote. If they're not afraid that their criminal behavior will land them in jail, what else will deter them? The result, they wrote, is 'a lack of conscience.' 