psychology notes for exam 2

psychology notes for exam 2 - through Sensation and...

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10-11-2007 through 11-6-2007 Sensation and Perception 1) Visual Agnosia a) Inability to recognize objects through sight b) Case of Dr. P i) “the man who mistook his wife for a hat” ii) Perfect vision iii) Lost the ability to assemble what he saw into a meaningful picture of the world iv) Visual sensation was intact v) Visual perception was severely impaired c) Sensation: take in sensory information i) Simulation of sense organs d) Perception: process (make sense of) sensory information i) Selection, organization, and interpretation of sensory input into something meaningful 2) Bottom Up and Top Down Processes: making sense of stimuli a) Bottom up i) Driven solely by input- the raw sensory data ii) Feature analysis: detecting specific elements in visual input and assembling them into a more complex form b) Top Down i) Driven by a person’s knowledge, experience, attention, and expectations 1
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ii) Using concepts to impose meaning on the individual elements c) Perception is an interaction between bottom up and top down processes 3) Thresholds a) Psychophysics i) The field that studies links between physical properties of stimuli and a person’s experience of those stimuli b) Transduction i) Transform physical energy into neural impulses where they are experienced as psychological events (e.g. light, sound, taste, smell, pressure) c) Absolute threshold i) The minimum amount of energy that we can detect ii) Define the boundary of an organism’s sensory capabilities d) Noise i) Irrelevant and competing stimuli e) Examples of absolute thresholds i) Vision: a candle flame seen at 30 miles on a dark, clear night ii) Hearing: the tick of a watch under quiet conditions at 20 feet iii) Taste: one teaspoon of sugar per 2 gallons of water f) Difference threshold i) How sensitive people are to differences between stimuli ii) Just Noticeable Difference (JND): the smallest difference in stimulation required to discriminate one stimulus from another 50% of the time 2
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g) Weber’s law i) The difference threshold is a constant percentage of the magnitude of the initial stimulus (1) Ex. Lifted weights, the JND is a change in either direction of 2% of the weight of the reference stimulus 4) Limitations of the Threshold Approach to stimulus detection a) Established under ideal conditions i) Often stimulus detection must be done under less than ideal conditions (i.e. “noise” present) (1) E.g. radiologists looking at x-rays for evidence of disease b) Assumes stimulus intensity is the major determining factor in stimulus detection i) Top-down processes may also play a role (1) E.g. expectations, concern over making mistakes 5) Signal Detection Theory a) Sensitivity to sensory stimuli relies on a variety of factors besides the physical intensity of the stimulus and the sensory abilities of the observer b) Other factors (higher decision stimuli): i) “noise” (i.e. distracting stimuli) ii) Experience iii) Concern over making mistakes Actual Stimulus Person says Prese nt Absent Prese Hit False alarm 3
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This note was uploaded on 03/27/2008 for the course PSY 202 taught by Professor Henriques during the Fall '08 term at University of Wisconsin.

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psychology notes for exam 2 - through Sensation and...

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