Detection, Discrimination, and the Theory of Signal Detection
There are many situations in which it is important to identify conditions that aid in the successful detection of stimuli. One example is the design of radar screens. Another is the design of instrument panels on airplanes, which are usually crowded, and so have to be designed so that some critical signals stand out. Psychologists and human factors engineers are employed to test conditions that maximize successful detection. Psychologists are also interested in the more general questions about what conditions are good and bad for detection, and what are the quantitative relationships between stimulus changes and detectability (suggesting laws of perception).
An early detection question that was asked, which gave birth to a classic form of research, is the question of how weak a stimulus can be and still be detected. A similar question, concerning discrimination, is, how slight a difference between two stimuli can permit the two stimuli to be distinguished? Questions about detection and discrimination have become somewhat more sophisticated with time, but the two basic forms of research the initial questions suggested are still recognizable in current research designs.
Questions of detectability are generally examined in a large series of trials, in which a specified stimulus is either present or absent on each trial. On each trial a subject is asked to decide whether or not the stimulus is present. The question is how much of the stimulus is required for the subject to hear it, or see it, or taste it, etc. The