you can see that this light-up-the-x-region-of-the-brain sort of approach makes people happy; it keeps giving nyt op-ed columnists the sense that they're talking about Science. i just want to make one remark about the 'pleasure center': obviously, pleasure (for example) is a hyper-primitive psychological term, and it is the psychology you bring into the experiment that determines the sort of result you're looking for, or what would count as a result, or what sorts of things we test. same with 'addiction,' and the idea that every problematic behavior or every habit of a human being is an addiction (kristof's position here, more or less) was an utter stampede before and completely outside the brainscan fad, which here is more or less an attempt to freeze a momentary paradigm or cultural formation as an eternal truth. as you may know, i would myself resist as extremely wrong the idea that addiction is a matter of pleasure. you'd be better off regarding it as a pursuit of pain, and i think the idea that addiction is the pursuit of pleasure is a view developed by non-addicts. but in any case the idea that, for example, you run marathons for the pleasure is extremely counter-intuitive, and it would occur to someone who was already in the grip of a 'theory' of human motivation (one which turns out non-explanatory, or is very dormitive-virtuey). 'pleasure' is the worst sort of psychological butchery or philistinism: there just is no such thing, really, and it stands in for anything that motivates anyone or anything that anyone pursues. we get it as a universal explanation from, you know, british utilitarianism, where it is the acme of all value etc. it was going to make human motivation comprehensible - or even, quantifiable - on a single principle. well now 'scientists' can pay off on bentham's hedonic calculus with their little light-ups. that a warm bath, kinky sex, a good burrito, cocaine, the sistine ceiling, money, and a five-mile run all cause the same sort of feeling is just false, and if you didn't already suppose that they must, somehow (because there is one thing in common to everything we pursue, and it's in the head of the pursuer), you wouldn't have 'found' these alleged structural similarities. that all these things must somehow be the same is something you brought to, not something you discovered in, the observations. indeed, none of these things are actually located (only) in the brain, and the whole thing presupposes an internalist theory of mind: what is real for you is what happens in your own little brain, which i want to to say is a bizarre picture. but don't worry. there will be a next paradigm.