The bed must be reserved as a place for sleep and sex only. That was the decree of psychologist Richard Bootzin in his influential 1972 proposal for a "stimulus-control" approach to better sleep. One central tenet was operant conditioning: The bed must be a sanctuary, such that the brain is trained to sleep when it is in the bed.
The allowance for sex—which, in its ideal form, is one of the most stimulating things a human body can experience—always seemed to me at odds with the stimulus-control approach. A note to aspiring self-help writers: The book For Better Sleep, Kitchen Sex remains unwritten. Otherwise, though, the idea of stimulus control made sense to a lot of people. It also included advice to avoid bedroom behaviors that abet anxiety, like clock-watching. And Bootzin's approach to insomnia endured, proving itself in several studies.
So last year when Charles Czeisler, a professor of sleep medicine at Harvard Medical School, found that around 90 percent of Americans use some kind of electronic device within the hour before bed—and correlated the degree of use with ever-poorer sleep—one of his first theories of the case was overstimulation. That's because, Czeisler and colleagues wrote in the Journal of Clinical Sleep Medicine in December of 2013, "In addition to making phone calls, cell phones now allow the user to instant message, listen to music, send emails, play games, and surf the Internet." So they do. And all of that stimulation, the researchers proposed, may "impede the natural withdrawal of sympathetic nervous system activity necessary for sleep onset." Or, they preclude chill.