"brain scans" depict no such thing. "10% activation in the brain" is probably a meaningless statement -- the brain is always doing "something" (except when it's

"brain scans" depict no such thing. "10% activation in the brain" is probably a meaningless statement -- the brain is always doing "something" (except when it's dead), and in any case, there's lots of different ways it might be getting "activated" (e.g., learning v.s. doing). That said, it's certainly possible to be mentally lazy, and this would no doubt lead to different patterns of activity than being mentally vigorous. Usually what these brain scans depict is, more or less, how "different" (brighter usually means larger statistical significance t-values) the oxygen-usage activity of some test state is from the same oxygen-usage activity during some rest state. Google fMRI (or look here: http://www.scholarpedia.org/article/fMRI http://www.scholarpedia.org/article/fMRI). Sometimes this means "less" activity than at rest state. Sometimes this means only very slightly (but consistently) more. Moreover, parts of the brain that vary considerably from trial to trial, but average out to a negligible difference from rest state, would also be easily ignored. This should give some sense of just how many assumptions and calculations have gone in to the pretty brain heat maps that the media are so fond of. Lots of good and interesting stuff can be and has been figured out using fMRI. That said, figuring out how the brain works using fMRI is like trying to figure out how an economy works by observing CO2 emissions from space, at a resolution of, say, 10m.