Imagine a product that increases alertness, boosts creativity, reduces stress, improves perception, stamina, motor skills, and accuracy, enhances your sex life, helps you make better decisions, keeps you looking younger, aids in weight loss, reduces the risk of heart attack, elevates your mood, and strengthens memory. Now imagine that this product is nontoxic, has no dangerous side effects, and, best of all, is absolutely free.

This miracle drug is, in fact, nothing more than the nap: the right nap at the right time. The work of Sara C. Mednick, Ph.D., a researcher at the Salk...