Download Color Vision: Trichromatic vs. Opponent-Process Theory - Prof. Constance Pilkington and more Study notes Psychology in PDF only on Docsity! October 6+8 11/02/2009 10/6/09 E. Color Vision 1. Young-Helmoltz Trichromatic theory o 3 kinds of cones o –each kind of cone is responsible for only one range of light waves o –color perception depends on relative activation of the cones 2. Opponent-Process Theory o a. 3 opponent systems (pair of color receptors) 1. Red-green 2. Yellow-blue 3. Black-white o b. in each pair the neurons- - are excited by wavelengths in the range of one color -when you stare, you exhaust the neurons -so if you stare at red, then you look away at a white screen, you will see green after-images occur because of sensory adaptation o c. color blindness (involves one of the system pairs) red-green, yellow-blue, black-white less than 1% of females and 5% of males will develop color blindness 3. So which theory is correct? o …both are at different levels o for cones, trichromatic theory is correct o but beyond the cones, opponent-process theory is correct IV. Gestalt psychologists (introduced the phase…) A. “the whole is greater than the sum of its parts” o How people organize incoming information o –if we draw 3 angles, we see a triangle B. 5 basic principles of organization o 1. Figure-ground differentiation (a visual experience) a.what we see in the center of our attention: The Figure b. the background of what we see and much less distinct: The Ground shows how sensation differs from perception we are capable of taking the same incoming data and organize it in a different way o 2. Similarity we tend to group elements like each other together o 3. Proximity we tend to see things that are close together and say they belong to each other o 4. Closure we favor the perception that creates a complete picture (we know it should be there so we fill it in) D. Integrative theories o You can’t really argue that it’s one or the other o Doesn’t take much to start top-down, in bottom-up they work together VI. Depth Perception We have to take cues from stimulus to perceive depth o A. Binocular uses(joint activity of both eyes) o The closer we get to something the more cross-eyed (so it’s parallel farther out) o Our brain uses this info about depth muscles around our eyes 2. Binocular Disparity o 3” apart (iris->iris) o the visual fields for each eye are different, so the retinal images will be slightly different o this difference is binocular disparity o Stereopsis to perceptually process the images in a way that contributes to depth B. Monocular cues o 1. Interposition if one object partially conceals other, the fully exposed object is perceived to be nearer or in front of the other object o 2. Aerial perceptive/Haze (the clarity of the image) the retinal images that appear sharp or distinct appear to be closer than objects that are blurry o 3. Elevation in the field, things that appear higher in the image appear farther away o 4. Linear Perspective systematically decreasing the size of elements and decreasing their space in the image (vanishing pt.) o 5. 2 similar objects, different sizes? The larger one appears to be closer to you 10/8/09 VII. The Skin senses (5) A. Receptors o Unevenly distributed; different areas are more sensitive B. Pressure o 1. Sensitivity on the body does vary lips and fingers are the most sensitive, legs and arms are the least sensitive o 2. Sex difference lower absolute threshold for women for general sensitivity, men and women are basically the same distribution o 3. Point localization: where exactly the pressure is being applied o 4. 2-point discrimination threshold method how far do 2 points need to be away from each other on you to realize that there are 2 points pressing down on you instead of one o 5. Accuracy is related to cortical representation of that body part the less cortical representation the less sensitive that body part is o 6. Sensory Adaptation yes we experience this, but it has to be at a constant level; so we partially adapt a lot but we rarely completely adapt C. Temperature (the temperature of an object when it touches your skin) o 1. Thermal sensitivity (unequally distributed) o lips and finger tips are the most sensitive o 2.Two separate systems (the receptors work separately from each other) a. hot receptors (activated by warmth) b. cold receptors (activated by cold) o 3.Warm: stimulation of warm is created by both preceptors o 4. Psychological zero (narrow range of temperature neither hot or cold) a. 33 degrees Celsius b. Why? The temperature of object and temperature of our skin (temperature of our skin is usually 33 C range or 91.4-95 F) Absolute threshold would be just below: 32.5 C o 5. Sensory Adaptation we do adapt to temperature the more extreme temperature, the more time it takes you to adapt (but we don’t really adapt to extreme temperatures) D. Pain 1. Stimulus ( damaging receptors) 11/02/2009 11/02/2009
