WE SEEM TO REGARD seven to eight hours of unbroken sleep as our birthright. Anything less means that something is awry. And people are willing to try anything to achieve that solid slug of slumber. Like a new-millennium version of Goldilocks, they try firm beds, pillow-topped mattresses and all manner of sleep systems to find one that is “just right.” They shun caffeine and change their diet—porridge and warm milk, anyone? They visit sleep clinics and swallow some $3 billion worth of sleeping pills every year.