Sensation _ Perception - lecture 2 - psychophysics

Sensation _ Perception - lecture 2 - psychophysics -...

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Sensation and Perception Lecture 2
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Galileo, Kant, and the rest are essentially “enemies” of psychology… Primary vs. Secondary Qualities. The senses which are deceitful. Mathematical knowledge = Ultimate knowledge.
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“Examining attentively what I was, I saw that I could conceive that I had no body, and that there was no world nor place where I might be; but yet I could not for all that conceive that I was not. On the contrary, I saw from the very fact that I
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Rene Descartes The Mind-Body Problem Descartes Position  Dualism. Made purely subjective experience respectable again.
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Measuring Perception First-person data vs. Third-person data Subjective vs. Objective. First-person data = subjective. Third-person data = objective.
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Measuring Perception Why can’t we just equate physical properties of a stimulus with the psychological experience of it? Identical physical stimuli can produce different perceptions. Different physical stimuli can produce identical perceptions. Physical = easy to quantify.
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Measuring Perception Physical stimulus produces a range of possible experiences …
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Measuring Perception Psychophysics The study of the relationship between the physical stimuli in the world and sensations about them we experience. Gustav Fechner Goal was to convert the Mind-Body Problem of philosophy into a problem scientists could work on.
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Fechner’s 3 Problems of Psychophysics Fechner’s 3 Problems of Psychophysics Detection  “Is something there?” Discrimination  “How is it different?” Scaling  “How much of it?” Can add a fourth problem … identification.
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Problem One: Detection Detection (“Is something there?”) How much of an energy change (stimulation) is necessary for an individual to detect a given stimulus? Absolute Threshold A critical level of intensity.
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Absolute Threshold
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Sensitivity Capability of detecting minor changes and/or differences in a stimulus. Relationship between threshold and sensitivity: Low Threshold vs. High Threshold. Threshold : Sensitivit y:
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Measuring Absolute Threshold Method of Constant Stimuli Stimuli presented many times in irregular (random) order. Task is to indicate whether stimulus is detected. Absolute  Threshol d
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Measuring Absolute Threshold Method of Limits Focuses only on stimuli near the absolute threshold. Descending Series = high intensity  low intensity. Ascending Series = low intensity  high intensity. Absolute threshold is an intensity somewhere between the last two stimuli presented.
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Measuring Absolute Threshold Adaptive Testing: Staircase Method Tracks threshold to be over time, taking changes in sensitivity into account. Method of Adjustment
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This document was uploaded on 11/04/2011 for the course PSYCH 301 at Rutgers.

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Sensation _ Perception - lecture 2 - psychophysics -...

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