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Psychology of Perception (PS 222) Week Two Notes

by: Sarah Kincaid

Psychology of Perception (PS 222) Week Two Notes 222

Marketplace > Psychology > 222 > Psychology of Perception PS 222 Week Two Notes
Sarah Kincaid

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Class notes week two
Psychology of Perception
Class Notes
nativism, Empiricism, Psychophysics, Graphs, EquationsExplained
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This 4 page Class Notes was uploaded by Sarah Kincaid on Thursday September 15, 2016. The Class Notes belongs to 222 at a university taught by Rucci in Winter 2016. Since its upload, it has received 70 views.

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Date Created: 09/15/16
2 | Measuring Sensations Key: = person = equation = term * = important guy Old Terms Nativism: knowledge and skills are innate Empiricism: knowledge comes from perception (our senses) New Stuff Qualia: subjective conscious experiences associated with percepts (ex: how purple the sky is) Change blindness: if we do not place fovea on the specific difference, we often miss the change (e.g. green pepper in “follow the coin”) This is because we make assumptions about world around us, especially anything outside the fovea. Because of this, if stuff changes slowly enough, humans will not notice (like the picture changing colors). Democritus  Defined the atom, smallest portion of matter  Perception is based on atoms coming in contact with us o olfaction - atoms in the air are coming into contact with receptors in nose Heraclitus 1. Panta Rei = everything flows  "you cannot bathe in the same river twice" Dualism: both mind and body exist as separate entities Monism: mind and matter come from same substance (aka principle of being) Materialism  physical matter is the only reality  everything (including the mind) can be explained in terms of matter & physical phenomena Mentalism  form of monism  mind is true reality  objects exist only in the mind's awareness Nativism & Empiricism People René Descartes  mind-body dualism  the universe consists of spirt/soul and matter/body (father of modern dualism)  spirit resides in pineal body in brain Thomas Hobbes: knowledge and imagination learned via senses John Locke: thoughts come from experience with collection of sensations George Berkeley  originally thought perception was limited to info available via eyes  but concluded that knowledge of world comes from experience, despite our limited perception  “esse est percipi” (For something to come into existence, it must be perceived.) Psychophysics People & Terms Just Noticeable Difference (JND) or difference threshold: smallest detectable difference between two separate stimuli or smallest detectable change in a single stimulus Two-point touch threshold: minimum distance at which two tactile stimuli (both simultaneous) can be distinguished Absolute Threshold : minimum stimulus intensity that can be detected 50% of time Ernst Weber  Weber's Law: JND is a constant proportion o DI = k I (difference of intensity = Weber fraction * intensity)  Weber fraction, k: constant proportion o Linear relationship between sensation magnitude and stimulus intensity o This means the JND of a quiet noise is much smaller than the JND of a loud noise. Gustav Fechner*  inventor of "psychophysics"  father of psychology (influenced by Wilhelm Wundt)  scholar of Weber  Psychophysics: science of defining quantitative relationships between physical & psychological (subjective) events  Panpsychism: all matter has consciousness (e.g. a rock feels like a rock)  Fechner's Law (aka Fechner’s scale) o S = k logI (S = sensation magnitude, I = stimulus) o Logarithmic relationship between sensation magnitude and stimulus intensity o Problem: NOT always true  Fechner’s inaccurate assumption: all JNDs feel the same (e.g. a weight change from 40 to 41 lbs feels the same as a weight change from 400 to 410 lbs)  "in order that the intensity of a sensation may increase in arithmetical progression, the stimulus must increase in geometric progression" Methods of estimating thresholds 1. Method of constant stimuli o HOW: stimuli with ranging intensity (barely perceptible to almost always perceptible) are randomly presented (100x for each stimuli) o WHY: to build a probability of sensation at each intensity o USEFUL: boring for subject and time-consuming for both subject and experimenter 2. Method of limits o HOW: test the magnitude of the stimulus from barely noticeable increasing until subject perceives stimulus, then repeat magnitude test from always noticeable decreasing until subject cannot perceive stimulus; alternate increasing and decreasing stimuli 4x each way o WHY: targeting 50% probability of sensation 3. Method of Adjustment o HOW: gives control to subject; manually adjusts stimulus magnitude o USEFUL: simplest, fastest, least reliable (subject usually goes over threshold) Magnitude Estimation  participant assigns values according to perceived magnitudes of stimuli (e.g. scale of 1- 10)  provide reference (e.g. if the darkness of square X is 10/100 what is the brightness of this square Y?) Stevens’ Power Law  S = k Ia  Power relationship between sensation magnitude and stimulus magnitude o more general than Fechner’s Law (logarithmic)  Problem: no way to verify this law correctly estimates sensation


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