Young children who are insensitive to fear are more likely to go on to commit crimes, according to psychologists. “Even at the tender age of 3, children who will go on to be convicted of a crime are less likely to learn to link fear with a certain noise than those who don't. This may mean that an insensitivity to fear could be a driving force behind criminal behaviour,” reports the New Scientist. Psychologists at the University of Pennsylvania in Philadelphia looked at data from a 1970s study which measured the sweat responses of 1,800 three-year-olds when they were exposed to different sounds – using sweat as an indication of fear. The psychologists checked if any of the subjects studied had gone on to acquire criminal records and found that the 137 that did were predominantly less fearful as children than their non-criminal counterparts.