Cost-effective crime fighting

From an interview of Steven Pinker on the Freakonomics blog:

There are many statistical predictors of violence that we choose not to use in our decision-making for moral and political reasons, because the ideal of fairness trumps the ideal of cost-effectiveness. A rational decision-maker using Bayes’ theorem would say, for example, that one should convict a black defendant with less evidence than one needs with a white defendant, because these days the base rates for violence among blacks is higher. Thankfully, this rational policy would be seen as a moral abomination. I suspect that the same sentiments would prevent any policy from pre-judging a child based on the behavior of his parents, whether one thinks the connection is due to genes or to parenting.

A review of the arguments against immigration would suggest that many people have no qualms using a similar Bayesian argument in shaping their immigration policy preferences.

Also from the same interview, which focuses on Pinker’s recently released book The Better Angels of Our Nature: Why Violence Has Declined:

Yes, I present extensive statistics showing the non-state peoples (hunter-gatherers, hunter-horticulturalists, pastoralists, and others living outside the control of states) have far higher rates of violence than modern states, even at their worst. I think this very long prehistory of life under anarchy probably selected for motives that can continue to lead to violence today, particularly dominance and revenge, both of which are adaptive in a state of anarchy but not in societies with well-functioning systems for nonviolent dispute resolution. This does not mean that we harbor a thirst for blood which must periodically be discharged—even the most bellicose societies modulate their violence, and can live for decades in peace. Evolution gave us motives that impel us to violence, such as greed, dominance, revenge, and the urge to mete out moralistic punishment, but it also gave us motives that undermine or control the violent inclinations, such as self-control, empathy, and reason—the better angels of our nature.

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