The Yerkes-Dodson Law
- Research shows that stress (called arousal in the field of psychology) can help you perform a task, because it heightens awareness.
- Too much stress, however, degrades performance.
- Robert Yerkes and John Dodson first postulated this arousal/performance relationship, and hence it has been called the Yerkes-Dodson law for over a century.

Arousal helps up to a point
- The Yerkes-Dodson law states that performance increase with physiological or mental arousal, but only up to a point.
- Research shows that the optimal amount of stress/arousal depends on the difficulty of the task.
- Difficult task requires less arousal to reach optimal performance, and will start to break down if the arousal level is too high.
- Simpler task requires more arousal and don’t fall off as fast.
Task Are More Stressful Than You May Think
- Don’t assume that people will use your product in a stress-free environment.
- Things that may not seem stressful to you as a designer might be very stressful for the person using your product in the real world.
- Men and women may react differently to stress.
- When stakes go up, errors may appear.