When: The Scientific Secrets of Perfect Timing

by Daniel H. Pink

Positive affect—language revealing that tweeters felt active, engaged, and hopeful—generally rose in the morning, plummeted in the afternoon, and climbed back up again in the early evening.

For you and me, the biological Big Ben is the suprachiasmatic nucleus, or SCN, a cluster of some 20,000 cells the size of a grain of rice in the hypothalamus, which sits in the lower center of the brain. The SCN controls the rise and fall of our body temperature, regulates our hormones, and helps us fall asleep at night and awaken in the morning.

First, our cognitive abilities do not remain static over the course of a day. During the sixteen or so hours we’re awake, they change—often in a regular, foreseeable manner. We are smarter, faster, dimmer, slower, more creative, and less creative in some parts of the day than others.

Other research has shown that time-of-day effects can explain 20 percent of the variance in human performance on cognitive undertakings.16

Third, how we do depends on what we’re doing. “Perhaps the main conclusion to be drawn from studies on the effects of time of day on performance,” says British psychologist Simon Folkard, “is that the best time to perform a particular task depends on the nature of that task.”

For analytic problems, lack of inhibitory control is a bug. For insight problems, it’s a feature. Some have called this phenomenon the “inspiration paradox”—the idea that “innovation and creativity are greatest when we are not at our best, at least with respect to our circadian rhythms.”