It's an afternoon class and most of the pupils are trying to fight off drowsiness -- an experience most people perhaps can identify with.

When students at Meizen High School in Kurume, Fukuoka Prefecture, start to get the nods, they do what comes naturally, and later wake up more alert.

Naohisa Uchimura, an assistant professor of neuropsychiatry at Kurume University in the prefecture, conducted a 40-day experiment at the high school in June and July to study the effects of taking a siesta in the middle of the school day.