Handout+Chap.+5

Handout+Chap.+5 - Sensation & Perception To represent...

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1 1 Sensation Chapter 5 2 To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation . When we select, organize, and interpret our sensations, the process is called perception . 3 Bottom-up Processing 4 Top-Down Processing 7 + + 7 5 Psychophysics Weight Pressure Sweet Sugar Volume Sound Brightness Light Psychological World Physical World 6 No Detection Intensity Absolute Threshold Detected Yes Yes No No Observer’s Response Tell when you (the observer) detect the light.
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2 7 Thresholds Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time. Proportion of “Yes” Responses 0.00 0.50 1.00 0 5 10 15 20 25 Stimulus Intensity (lumens) 8 Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock 9 Difference Threshold Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold Tell when you (observer) detect a difference in the light. No Observer’s Response No Yes 10 Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Constant (k) Stimulus 3% Tone 2% Weight 8% Light 11 Signal Detection Theory (SDT) Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). 12 SDT Matrix Correct Rejection False Alarm Absent Miss Hit Present Signal No Yes Decision
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3 13 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. 14 Transduction The transformation of stimulus energy into neural impulses. Phototransduction: Conversion of light energy into neural impulses that the brain can understand. 15 Visible Spectrum The Stimulus Input: Light Energy Both Photos: Thomas Eisner 16 Wavelength (Hue) 17 Wavelength (Hue) 400 nm 700 nm Long wavelengths Short wavelengths Violet Indigo Blue Green Yellow Orange Red 18 Intensity (Brightness)
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4 19 Intensity (Brightness) As intensity increases or decreases, color
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This note was uploaded on 04/03/2008 for the course PSYC 7A taught by Professor Staff during the Winter '99 term at UC Irvine.

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Handout+Chap.+5 - Sensation & Perception To represent...

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