Comment by Cruzc09 on Meetup report: How harmful is cannabis, and will you change your habits? · 2012-09-09T14:55:27.898Z · LW · GW

Also, marijuana severely decreases motivation and level of motivation has been correlated with IQ. With frequent usage of any drug, I would say it would modify behavior. This is to say, if you get hi a lot, it probably would modify your normal behavior just from the basis of habitual formations. Am I correct to assume this?

There could also be self-fulfilling prophesies in the taking of the exam. Telling a guy, "You're a stoner, so we want you to taken an IQ test" probably does something to the test takers perception of himself/herself.