A few years ago, when Michael Scullin started teaching a class on sleep at Baylor University, he noticed a frustrating trend: his students were learning how detrimental sleep deprivation could be, but they never changed their habits. Many slept only five hours a night.  Scullin, director of Baylor’s Sleep Neuroscience and Cognition Laboratory and assistant professor of psychology and neuroscience, took it a bit personally, he said half jokingly in an interview. And so he issued a challenge.