I don't mean this in a self congratulatory fashion, its just the result of a couple of years of observation on the trail and at the LBS. The observation is that bicyclers seem to be noticeably sharper on average than the general population. Not sure what is cause and what is effect though. It may just be that people who are concerned with fitness are a standard deviation or so above the mean. Maybe it's a function of the subset of people with sufficient discretionary income to be willing to buy bikes costing $thousands.
But, almost without exception, when I meet someone in a biking context, they are bright. Not saying it is a sport populated by geniuses but definitely noticeably above the mean.
BTW: I refer to sport bikers as opposed to those biking because they lost their license.