The more you earn, the lower your IQ. That's the clear but unexpected result from the second National IQ test broadcast by the BBC. The test is still online if you are curious. The first test was discussed here. For a higher IQ, be an unemployed Irish man and drink too much.
Musicians are really smart. They have larger and more sensitive brains than non-musicians, and their collective IQ is much higher. They have 130% more grey matter in one area of their auditory cortexes. The question of how this explains Ozzy Osbourne nonwithstanding, I'll bet if you're really, really smart, you could be one of the new members of Men Without Hats. Must be very knowledgeable in midi, sequences, and sampling.
Breast-feeding increases babies' IQ by 3-5 points, compared to the babies fed with formula. This is probably for two reasons: better nutrition and maternal bonding. Premature babies receive the greatest benefits.
Kids are smarter than ever before, AOL chat transcripts notwithstanding. It seems to me that the fact that IQ tests measure culture acquisition as much as anything else may explain a lot of this, but I wonder if there may not be something to the "visual literacy" idea: are we (as a species) building a new type of perception, or honing old cognitive tools into something which might as well be new? And, if so, where might it lead us?