measure of risk, a factor that both juvenile and adult courts should be using to determine their sentencing, especially the individual’s future dangerousness. Individual differences in glucose metabolism, together with relative differences in brain activity, lead to stable differences in self-control. But there’s more, both luck of the draw genetic effects and clinical distortions. Recall that the low expressing form of the MAOA gene results in lower levels of serotonin which, in turn, leverages less control over aggressive impulses. There is another gene — SLC6A4 — that also comes in two forms and regulates the level of serotonin. The short form of this gene gives you less serotonin, is commonly found in pathological gamblers and psychopaths — two heavily male-biased disorders that are associated with impoverished impulse control. Psychopaths also have relatively smaller frontal lobes , especially within a region that has a high density of serotonin neurons. Psychopathy is joined by a family of impulse control disorders that also implicate dysfunction of the serotonin system, including kleptomania (stealing), pyromania (burning), trichotillomania (hair pulling), and oniomania (shopping). Like glucose, serotonin plays a lead role in our capacity for self-control. When serotonin is sidelined from the performance, any number of impulsivity problems may emerge. What I have said thus far is only a partial accounting of the biological ingredients that figure into our capacity for self-control. What this partial recipe tell us is that regardless of the situation, some individuals are inoculated against the pull of authority and group ideology and others are susceptible. If you missed the inoculation clinic in utero, you are more susceptible to temptations and excesses, including excessive violence. This is important for our interpretation of the real world and of the famous psychological experiments by Milgram, Zimbardo, and others in which seemingly good people carried