Sensation _ Perception - lecture 3 - signal detection theory and error management theory

Sensation _ Perception - lecture 3 - signal detection theory and error management theory

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Unformatted text preview: Signal Detection Theory Any stimulus must be detected against a background of internal noise in our sensory systems and external noise in the environment. There is no absolute threshold. Signal Detection Theory Absolute threshold varies not only with changes in an sensitivity, but also with changes in the decision making process (decision criterion). Signal vs. Noise Trials Perceived difference between these types of trials must be small. Signal Detection Theory Signal Detection Theory Detection Sensitivity (Accuracy) Criterion (Response Bias) Signal-Detection Theory Observers Response Signal: Yes: No: Present (Signal + Noise Trial) Hit Miss Absent (Noise Trial) False Alarm Correct Rejection Signal-Detection Theory Response Signal: Approach: Avoid: Attraction Hit Miss No Attraction False Alarm Correct Rejection Signal Detection Theory Signal Detection Theory Criterion ( ) Simple decision rule an observer bases their response on. Motivation and expectation will determine where the criterion is placed. http://cog.sys.virginia.edu/csees/SDT/index.html Signal-Detection Theory: Effects of Expectation Response Signal Yes No Present 0.95 0.05 Absent 0.63 0.37 Stimulus Present 90% of the Time Signal-Detection Theory: Effects of Expectation Response Signal Yes No Present 0.35 0.65 Absent 0.04 0.96 Stimulus Present 10% of the Time Signal Detection Theory The Criterion ( ) A quantitative measure of an observers decision criterion independent of their sensitivity ( d ). Changes in an observers response strategy can change the proportions of hits and false alarms. Stricter criterion leads to fewer false alarms but more misses. Signal Detection Theory Sensitivity ( d ) Represents a quantitative measure of an observers accuracy independent of their decision criterion. Depends on the separation and the spread of the noise and signal + noise distributions. SDT and Outgroup Identification Allport & Kramer (1946) Anti-Semites correctly identified more Jewish faces as Jewish and more non-Jewish faces as not Jewish than unprejudiced participants. Lindzey & Rogolsky (1950) Replicated Allport and Kramers results. Vigilance Hypothesis. SDT and Outgroup Identification Carter (1948) Suggests Allport and Kramers (1946) results were obtained due to a response bias. Elliot & Wittenberg (1955) Response-Bias Hypothesis. SDT and Outgroup Identification Dorfman & Keeve (1971) Accuracy is function of both response bias and sensitivity (signal-detection theory)....
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Sensation _ Perception - lecture 3 - signal detection theory and error management theory

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