Lots of factors constantly affect a person's active IQ-- That's why they always tell you to "get ready for an exam" because hunger, sickness, stress, poor air quality (and thus mouth breathing) and with previously mentioned stress-- other emotions/feelings, anger, sadness, lust; It is expected that you prepare to put all of that aside along with your studies to give the most proper measurement.<br>And let's be honest, many of us are playing with those other factors in a way to give ourselves another excuse. <b>Or... or structure also breeds a better environment to become more intelligent</b>