Psy 342: Review for Exam 2
The Visual Cortex and Beyond
Visual pathway: Retina
V1 (striate cortex)
Hubel and Wiesel (Nobel Prize) individual cell recording from V1
Simple cells (straight lines),
complex cells (motion), hypercomplex cells (edge detectors)
Mishkin: What (ventral to temporal lobe) and Where (dorsal to parietal lobe) pathways
Damage to What pathway causes agnos
ia (lack of object recognition) : prosopagnosia (face recognition)
o Where pathway on right hemisphere may lead to contralateral neglect (lack of attention to left side)
Perceiving Objects and Scenes
Problems in designing a perceiving machine
Viewpoint invariance: same object when viewed from different angles
Structuralism (perceive world by adding up the elements of sensation)
Gestalt (whole is greater than the sum of its parts) Ex. Apparent motion
Gestalt laws: Pragnanz (good figure), similarity, continuation, proximity, common region, common fat
Figure ground principles
: more “thinglike”, figure in front, contour belongs to figure, lower part seen as figure.
Why is selective attention necessary?
Eye movements: saccades (small eyes movements). Three fixations a seco
by stimulus salience, knowledge about scene, nature of task, past learning.
Reddy experiments with central, peripheral and joint tasks. Do well on one task. Joint task: faces better than colored disks
Inattention blindness (Simons and
Chabris): 46% failed to see gorilla in film
Change blindness: fail to see changes in scenes. Continuity errors in films. Objects change without movement.
Attention people with autism tend to focus on things rather than people’s faces or actions. Problem
Chap. 9 Perceiving Color
Red, yellow, green and blue are primary colors. Part of visual spectrum.
Brown and purples are extraspectral.
Change color by altering intensity (brighter or dimmer) or saturation (by adding white)
based on wavelengths that are absorbed, reflected or transmitted (thru tinted glass and liquids)
Additive (projected lights) and subtractive (mixing paints) color mixing.
Helmholtz theory of color vision. Trichromatic theory. Three cones with different wavelength
Color deficiency. Monochromats (no cones), Dichromats (two cones).
Protanopia and Deuteranopia (sex
linked, mostly males, red
Tritanopia (not sex
Process theory of color vision. Red+green. Blue+yellow. Black+white. Evidence in afterimages.
Both theories work together. Trichromatic at retina. Opponent process in brain.