Signal Detection Theory: A theory in psychology which characterizes not only the acuity of an individual’s discrimination but also the psychological factors that bias the individual’s judgments. Failure to separate these two aspects of discrimination had tempered the success of theories based upon the classical concept of a sensory threshold. The theory provides a modern and more complete account of the process whereby an individual makes fine discrimination. The capacity to discriminate stimuli is based on physical energy, and external factors such as costs and benefits.
Signal Detection Theory is a statistical technique designed to locate a signal against a background of noise. This theory states that there are no absolute thresholds for sensations. In addition it describes one of the more important cognitive tasks the brain performs. Every sensory organ in an animal is exposed to a variety of stimuli. Most of this will be noise or meaningless information, but some of it will be highly valuable and informative. The background stimuli are noise, while the information is a signal. The nervous system and primarily the brain use various algorithms to attempt to detect these signals.
In basic signal detection theory there are two possible states for a signal: present or absent. Individuals attempting to detect the signal will either say it is present or absent. Combined that leads to four possible combinations, labelled as follows:
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