Yerkes-Dodson law

Meaning: The law links arousal (alertness and physiological activation, such as that produced by stress, excitement or stimulation) to performance. With very low arousal, motivation and attention are poor. With very high arousal, anxiety narrows attention and interferes with working memory, so performance falls. Peak performance falls between these extremes.

The peak shifts with the task. Simple or well-learned tasks (a practiced routine, a basic physical task) are performed best at relatively high arousal. Complex, novel or difficult tasks (learning unfamiliar material) are performed best at relatively low to moderate arousal.

On the MCAT: A passage may describe participants doing an easy task and a hard task under different levels of stress, noise or incentive, then show a graph. Expect two inverted-U curves, with the hard-task curve peaking to the left of the easy-task curve. You may be asked which condition gives the best performance, or what happens to a person who is already highly anxious and then faces a difficult task. Test anxiety and performance under pressure are common settings.

Common confusion: Students often read the law as "more arousal, better performance," a straight line. It is a curve with a peak, and performance declines past that peak. Another slip is placing the peak at the same arousal level for every task. The fact that settles it is that task difficulty moves the optimum: harder task, lower optimal arousal.