This comment is relevant; we have a dataset of users who both took the Raven's test and self-reported IQ. The means of the group that did both was rather close to the means of the group that did each separately, but the correlation between the tests was low at .2. If you looked just at responders with positive karma, the correlation increased to a more respectable .45; if you looked just responders without positive karma, the correlation was -.11. This was a small fraction of responders as a whole, and the average IQ is already tremendously inflated by nonresponse. (If we assumed that, on average, people who didn't self-report an IQ were IQ 100, then the LW average would be only 112!)