A discussion of four errors which lead to false positives-- neglecting maturation (that brains change with time, even without intervention, learning effects (people who take a test more than once get better at it), regression to the mean (people who are unusually good or bad at something will probably have a more average score on subsequent attempts), and the placebo effect.

The link above is a summary of a lecture which isn't playing for me, so any further information about the lecture would be greatly appreciated.