neglect reduce the size of the amygdala. for whatever reason, i don't think psychopaths have to be born with an amygdala that is three sizes too small. if that brain impairment predisposes them, raises the odds of them doing the terrible things they do the fascinating question is, do what extent do we hold them fully responsible for that action. >> we are going return to this. we're going to have a program on this. this is not dna evidence this is not like saying i'm responsible, david is not. definitively here this is a problemmistic statement. and that is imperfect in front of the law. >> absolutely. >> so i think as techniques get better and we see that not only the amygdala the amygdala associated with this abnormallality, that means danger associated with another abnormallality it's unwe lated then we'll be in a better position. >> rose: are there places in cases where it's not just within an individual but their violence becomes in some way contagious within a society or within a group? so when we look at cases of geno

the prefrontal cortex, the amygdala and the hypothalamus.he prefrontal cortex deals with character formation. it can lead to an increase in aggression. the ventral striuatatum deals with other kinds of aggression. the hypothalamus has many functions, but we are going to focus in particular on its role in aggression and sexuality. we have on this program, as you pointed out, five fantastic people. we have david anderson, who i have known for a long time, who pioneered a study on aggression and its relation to sexuality. we have richard tomly, who was interested in the development of aggression. johan has spent a career studying how victims respond to aggression. we have emil a psychologist like myself, competent [laughter] who is interested in psychiatric interests. and we have adrian who is interested in premeditated aggression, which is a different entity. we have not only an extremely important topic, perhaps the most important topic confronting all of us today, but we couldn't have a better group of people discussing it. so we are in for

this is the amygdala on the left.hat we find when we study cold-blooded offenders psychopaths, they have a shrinkage in the amygdala. it is reduced in size by 18%. himit is reduced in size by 18%. to on the right, the areas that are actually physically deformed. the amygdala is very important in generating emotions. a shrinkage will reduce fear. what stops us from breaking the law? when we are threatened with the punishments we would get if we were caught. when you have this impairment that normally produces this fear that stops us, you are more likely to commit offenses in a cold-blooded fashion. there is more to it than that. there is yet another brain region called the ventral striatum. you can see there is greater activity in psychopaths when they are anticipating rewards. psychopaths are reward driven. they want the goods. just like an addiction. charlie: it is a stimulation to the brain? adrian: the idea is the brain that gets hopped up on reward is firing a lot more. maybe that is why they are more likely to pu

at the front of it is this thing called the amygdala. it's very important for fear.'re more fearless. you're able to approach things and do things that you wouldn't before. >> reporter: andy estimates heather had sex with about ten other men, but behaved inappropriately with as many as 50. >> heather at the time, she couldn't see that there was anything sort of out of the ordinary and that she didn't think she was doing anything wrong. she's, like, "well, why -- why -- why can't i?" >> reporter: didn't matter how old they were, didn't matter -- >> no. >> reporter: -- how handsome they were -- >> no. >> -- it wasn't about the guys. it was about her. >> it was almost like a sport, you know, going out and seeing if there was -- >> anybody around. >> yeah. >> reporter: in vancouver, alissa is also trying to manage a new sexual personality. which she traces to a car crash in 2008. >> the car flipped over three times. i hit my head, and the next time i woke up was in the morning in the hospital. >> reporter: she had been a typical teenager, she says, interested in fashion