Productivity gurus claim that the best time of day to perform different types of cognitive tasks varies substantially based on the body’s biological clock, but a new study led by sleep scientists challenges this long-held belief. The researchers analyzed data from a laboratory experiment that put participants on either a simulated day or night shift schedule for three days, allowing them to dissociate the biological clock effects on task performance from the effects of how long the participants had been awake. After completing their shifts, participants were kept in a 24-hour constant routine protocol designed to study humans’ internally generated biological rhythms independent of any external influences. Comparing participants’ performance on three distinct cognitive tests completed throughout the constant routine, the researchers found that the timing of peak performance was not task specific.