Signal detection theory proposes a way to measure perceptual sensitivity (how effectively the perceptual system represents sensory events) separately from the observer’s
decision-making strategy. It explicitly takes into account observers’ response tendencies, such as liberally saying yes when there is any hint of a stimulus or conservatively
reserving identifications only for obvious instances of the stimulus. Even when one
person says yes much more often than another, both may be equally accurate in distinguishing between the presence or absence of a stimulus.