Researchers point to the physicians’ circadian rhythms that make focusing harder in the afternoon. Similarly, studies of colonoscopy accuracy (colonoscopies were once artfully described to me by a friend as the art of having a garden hose stuck up your butt) show that endoscopists detect polyps (the growths that can indicate cancer) at a lower rate as the day progresses. Every hour produces a 5 percent reduction in detection.4
