New imaging technologies make it possible to watch different parts of the brain activate as a subject thinks about -- oh, say, the war in Iraq or Cameron Diaz.
A recent paper in the journal Science describes experiments with subjects who administer punishment to "norm violators," that is, to other people who break the rules. Certain parts of the punisher's brain light up like a Christmas tree.
Apparently, it feels good in a deeply satisfying, hardwired way, to see someone punished for cutting in line or cheating at cards.
In a civilized society, we no longer whack unruly school children or stone adulterers, but we still have those parts of the brain that love to see the baddies get their just desserts.
Which may be why a wicked grin crossed my face today when on my early morning walk through quiet conservation land I passed a kid with a broken-down three-wheel all-terrain vehicle.