"Science identifies three types of people. Name them?" Without context this seems like a nonsense question (Short, dark haired, Beatles fans?). But it was asked during the recent FIDE Trainers course in Baku, and fortunately there was context. For those playing at home, the correct answer is "Larks, owls and Arrhythmics" The context was the time of day people operate best in (Early, late, or middle).
Now a new study has looked at this as applied to decision making. Using online blitz chess as a data source, the study looked at when people made good or bad decisions. Studying thousands of 2 or 3 minute games in FICS, the study reported that we make worse decisions as the day wears on, with mid-afternoon seeming to be when it plateaus out. The study looked at both the time to make a decision, and how good that decision was. On average players were more cautious earlier in the day (moving slower but more accurately), and played faster, but less accurately in the afternoon.
Nonetheless the study did not say that we have better results early in the morning (as good and bad decisions may not effect the overall result of the game), so if you feel comfortable playing from 10pm to 4am (as opposed to getting out of bed at 6:30am), there is no need to change you sleeping habits for the sake of a few rating points.