The Yerkes-Dodson law shows that there is a close link between arousal and performance. According to this law, performance on tasks is best when arousal level is appropriate to the difficulty of the task. Performance on tasks is best when the arousal level is appropriate for the difficulty of the task. For simple tasks, performance is better when arousal is especially high. Complex or difficult tasks are accomplished best when arousal is lower. Performance suffers when the arousal level is either too high or too low for the task.