SENSATION AND PERCEPTION

SENSATION AND PERCEPTION - SENSATION AND PERCEPTION...

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SENSATION AND PERCEPTION HISTORICAL PERSPECTIVE Ernst Weber (1834): published book called De Tactu that investigated muscle tense -recorded the Just Noticeable Difference in sensation Gustav Fechner (18 th -century): discovered relationship between physical stimuli and psychological responses to stimuli -formulated Weber’s Law Sir Francis Galton: -measured sensory abilities of 10, 000 people over six years Max Wertheimer (1880-1943): -founded Gestalt Psychology beginning with phi phenomenon -experience of the illusion has wholeness that is much more than sum of its parts PSYCHOPHYSICS- -study of relationship between physical stimuli and psychological responses to stimuli ABSOLUTE THRESHOLDS: -minimum of stimulus energy needed to activate a sensory system -how little and can still be perceived -also called limen => subliminal perception refers to perception of sub-threshold stimuli without conscious awareness Difference Thresholds: -how different in magnitude stimuli must be before they are perceived to be different -have standard stimulus and comparison stimulus: subjects task is to adjust comparison stimulus until it matches standard stimulus; repeat trials and average difference between standard and comparison => difference threshold -Just Noticeable Difference: amount of change necessary to predict the difference between two stimuli (if difference threshold is 2, then 2 would be 1 JND; 4 = 2 JND) -Weber’s Law: ∆I/I = K or ∆S/S = K; change in intensity divided by intensity; smaller the K, better the sensitivity; law fits the data except at very low or very high intensities Fechner’s Law: expresses relationship between intensity of the sensation and the intensity of the stimulus; sensation increases more slowly as intensity increases Steven’s Power Law: intensity of the stimulus to the intensity of the sensation, has to do with subjective responses from subjects Signal detection theory: -response bias: tendency of subjects to respond in a particular way due to nonsensory factors -signal detection gives us way to measure how well the subject can sense the stimulus (sensitivity) and response bias -experiment: stimulus presented or not presented; even without stimulus you can still sense noise; stimulus is called signal; subject asked to tell whether or not they sense the signal
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-Four possible choices: hit, miss, false alarm, correct negatives -Receiver Operating Characteristics (ROC): curve that graphically summarizes subject’s response by measuring the sensitivity characteristic of a subject receiving signals
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SENSATION AND PERCEPTION - SENSATION AND PERCEPTION...

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