In the general population there is a correlation between athletic ability and intelligence. People who are are athletically more capable tend to be smarter as well. But student athletes in US colleges have a reputation for being less intellectually and academically capable. The explanation for this is pretty simple. Athletes benefit from affirmative action. If you are really good at sports then you can get into a much better college than you could on the strength of your academic record alone. The result is that student athletes, whether they are in a top schools, or mediocre schools, are noticeably dimmer than the average student at a given school. Call that the "jock effect". Affirmative action gives athletes an undeserved reputation for being dim witted, because it consistently places them among groups of students who are brighter.
Now one of the arguments for racial affirmative action in college admissions is that it helps to break down racial stereotypes and racial barriers by exposing all students to a diverse array of students from different races and backgrounds. The problem is that the jock effect happens with racial affirmative action as well. Thanks to racial affirmative action in admissions black students can get into better colleges than they would on the strength of their academic records alone. As a result, the black kids that white kids get to meet at college are, on average, significantly dimer and less successful than other kids at the same school. I doubt if that really helps to break down racial stereotypes or racial barriers.
