Jonah Lehrer answers:

...learning about the brain can help constrain our theories. We haven't decoded the cortex or solved human nature - we're not even close - but we can begin to narrow the space of possible theories. We know, for instance, that the rational agent model of Homo Economicus isn't particularly accurate, at least from the perspective of the brain, and that the deliberative prefrontal cortex is often out-shouted by emotional brain areas like the nucleus accumbens, insula, etc. This supports, of course, lots of observational studies that demonstrate that people rarely rely on explicit calculations of utility (or explicit calculations of anything, really) when making decisions. The anatomical details, in other words, can help settle the argument.

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