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SIGNAL PROBABILITY AND VIGILANCE: A REAPPRAISAL OF THE ‘SIGNAL‐RATE’ EFFECT
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1969
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Detection TheoryEngineeringBehavioral MeasurementVisual Perception (Experimental Psychology)CognitionPerceptionAttentionSocial SciencesPsychologyVisual TaskVisual CognitionCognitive ElectrophysiologySignal DetectionPsychophysicsBehavioral SciencesCognitive ScienceFalse Report RateVisual ProcessingExperimental PsychologyVisual FunctionVisual Perception (Computer Vision)Signal ProbabilityTime Perception
Signal detection theory explores how the probability of a signal influences perceptual performance. The study examined how varying signal probability affects performance on a 40‑minute visual task. Participants were assigned to separate groups tested at five signal probability levels (0.02, 0.06, 0.18, 0.24, 0.36). Detection rates rose with signal probability, accompanied by higher false alarm rates, indicating that probability shifts the criterion (β) rather than sensitivity (d′).
Performance on a 40 min. visual task was studied as a function of signal probability. A separate group was tested at each of five levels of signal probability (0·02, 0·06, 0·18, 0·24 and 0·36). Percent detections increased with signal probability. This increase was accompanied by a rise in the false report rate, and analysis in terms of signal detection theory suggested that signal probability affects the subject's criterion (β) rather than his ability to discriminate ( d ′).