Many a time we all have faced it while sitting in a class. During lectures we have a strong urge to sleep (rather we make a strong effort not to fall asleep. Especially if you are seated in the front rows.) It is not just boredom. I feel it is only when we want to concentrate, we tend trio fall asleep. If the lecture is boring my mind wanders and I don't feel sleep! Is there any study conducted on this phenomenon?