In The Cloud Minders Kirk is forced to "Dig as the troglodites do." though he is trying to convince the woman he's with that "something he can't see" will lower his IQ because the gasses have a certain affect on the brain. It occurs but I always believed that things like that took two things 1. time and 2.exposure so it would be unrealistic that it would happen in about 4 or 5 hours. Besides the fact that it's Star Trek is there any proof that it could happen in such a short time?