A new study in mice might help to explain why it's so hard to drift off to dreamland when you're engrossed in a page-turning book.
Researchers from the University of Texas Southwestern Medical Center found that mice that were kept awake by appealing to their curious natures had a harder time falling asleep than mice that were just gently kept awake — even when both groups of mice were sleep-deprived.
"This study supports the idea that subjective sleepiness is influenced by the quality of experiences right before bedtime. Are you reluctantly awake or excited to be awake?" study researcher Dr. Masashi Yanagisawa, a professor of molecular genetics and a Howard Hughes Medical Institute investigator at the university, said in a statement.