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Psychology December Final.docx

Psychology December Final.docx - Psychology December Final...

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Psychology December Final Sensation and Perception Sensation The process by which our sense organs respond to and translate stimuli into nerve impulses sent to the brain Perception Organizing the stimulus input and giving it meaning Stages of sensation and perception Stimuli activate sensory receptors Sensory receptors translate information into nerve impulses Specialized neurons analyze stimuli features Stimulus pieces are reconstructed and compared to stimuli in memory Perception is then consciously experienced Psychophysics Absolute limits of sensitivity Dimmest light in which we can see objects Softest sound we can hear Recognizing differences between stimuli Smallest difference in brightness detectable Recognizing differences between tones Stimulus Detection The absolute threshold The lowest intensity at which a stimulus can be detected 50% of the time The environment contains a background level of stimulation for each sense and this level (the ADAPTION level) must be overcome if a stimuli is to be detected The differential threshold The amount of energy required to overcome the Adaption level. It is subject to variation with changes in circumstances Locke’s experiment o Materials: 3 buckets/large bowls o Method: fill 1 with very hot water; fill 1 with very cold water; fill 1 with tepid water o Procedure: subject closes eyes, place one hand in hot and the other in cold for approx. 3 minutes, then place both hands in tepid water, ask subject to report sensation for each hand separately, instruct subject to open eyes o Although both hands are in the same water the sensations differ due to the prior ADAPTION Signal Detection Theory Decision criterion A personal standard of certainty before a person will say that they detect a stimulus
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Affected by o Conservativeness or boldness o Increasing rewards for hits or costs for misses o Bold subjects show high hits and high false alarms o Conservative subjects show high misses and correct rejections o Criterions can be manipulated by changing the payoff for each cell of the response matrix (hit 10 cents, miss minus 10 cents, false alarm minus 1 cent, correct miss 5 cents) o This shows perception is, to some extent, a decision Subliminal Perception A subliminal stimulus cannot be perceived consciously but do register in the nervous system o “Subliminal” advertising during a movie (Vicary’s Claim) Stimuli above threshold influence behaviour much more than subliminal stimuli Subliminal stimuli have stronger effects on attitudes Effects may be due to placebo effects Difference Threshold Just noticeable different, is the smallest difference between two stimuli that people can perceive 50% of the time o Weber’s Law: the just noticeable difference is directly proportional to the magnitude of the stimulus with which the comparison is made (1/50 for weight) o The smaller the fraction the less change is necessary to produce a just
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