Signal Detection Theory explains how individuals differentiate meaningful stimuli (signals) from background noise in ambiguous conditions. Originating from radar research, SDT has been adopted in psychology to explore perceptual decision-making.
Signal vs. noise
Signal: The specific target an individual tries to detect.
Noise: All additional, irrelevant stimuli that may obscure the signal.
Detection outcomes
Hit: Correct identification of a present signal.
Miss: Failure to detect an existing signal.
False alarm: Belief in a signal when none is present.
Correct rejection: Accurate perception that no signal is present.
Sensitivity (d′)
Represents how effectively someone can tell signal apart from noise; greater d′ means better discrimination.
Criterion (β)
The subjective threshold a person sets to decide if a signal is present, shaped by bias, expectations, or cost-benefit considerations.
Applications
Perception studies: Understanding detection of visual or auditory stimuli under varying conditions.
Memory research: Distinguishing between old (familiar) and new (unfamiliar) information.
Decision-making: Exploring how uncertainty impacts judgments, given both sensory ability and personal criteria.
Influencing factors
Stimulus intensity: Stronger signals are easier to detect.
Environment: Background noise or distractions hamper detection.
Psychological state: Attention, motivation, and fatigue can alter sensitivity.
Sensory adaptation
Sensory adaptation (or neural adaptation) describes the gradual reduction in responsiveness to a constant stimulus, enabling organisms to redirect their attention to changing inputs in the environment.
Examples
Olfactory adaptation: A strong odor becomes less noticeable over time.
Visual adaptation: Eyes adjust when moving from bright light into darkness.
Tactile adaptation: Wearing a watch or ring is initially noticeable, then fades.
Distinction from habituation
Sensory Adaptation: A physiological change at the receptor level.
Habituation: A psychological process reducing behavioral response without necessarily altering sensory receptor function.
Functional Importance
By ignoring static, unimportant stimuli, organisms conserve resources and remain primed to detect new events or potential threats, enhancing survival.
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