inverted-U hypothesis
a proposed correlation between motivation (or arousal) and performance such that performance is poorest when motivation or arousal is at very low or very high states. This function is typically referred to as the Yerkes–Dodson law. Emotional intensity (motivation) increases from a zero point to an optimal point, increasing the quality of performance; increase in intensity after this optimal point leads to performance deterioration and disorganization, forming an inverted U-shaped curve. The optimal point is reached sooner (i.e., at lower intensities) the less well learned or more complex the performance; increases in emotional intensity supposedly affect finer skills, finer discriminations, complex reasoning tasks, and recently acquired skills more readily than routine activities. However, the correlation is considered weak; at best, the inverted U-function represents an entire family of curves in which the peak of performance takes place at
different levels of arousal.