Sensation & Perception Flashcards
cornea
gathers & focuses incoming light
clear, domelike window in front of eye
pupil
hole in iris, contracts in bright light, expands in dim light to let more light in
iris
colored part; has involuntary muscles, controls size of pupil
lens
behind iris, helps control curvature of light coming in & can focus near or distant objects on retina
retina
screen filled with neural elements & blood vessels
- very back of eye
- image-detecting part
duplicity theory of vision
retina contains two kinds of photoreceptors
where is the blind spot in the eye?
where optic nerve leaves the eye; no photoreceptors here
cones
used for color vision & fine detail
- most effective in bright light
- chromatic & achromatic colors
both begin with c
rods
function best in reduced illumination; allow perception only of achromatic colors - low sensitivity to detail; not involved in color vision
fovea
contains only cones
so…visual acuity best here & fovea is most sensitive in normal daylight vision
are there more rods or cones in the eye?
rods
describe connection between receptors & optic nerve
rods & cones –> bipolar neurons –> ganglion cells
ganglion cells group together to form
optic nerve
neurons in the eye
horizontal, amacrine, bipolar, ganglion
optic chiasm
fibers from nasal half of retina cross paths; fibers not on nasal side DON’T cross paths
nasal fibers
fibers that cross at chiasm, closer to nose
temporal fibers
fibers on outside of eyes, don’t cross at chiasm
info from left visual field is processed in
right cerebral hemisphere
where does info go after the optic chiasm?
lateral geniculate nucleus of thalamus –> visual cortex in occipital lobe –> superior colliculus
Hubel & Wiesel
feature detection theory
feature detection theory
certain cells in cortex are maximally sensitive to certain features of stimuli
simple cell (feature detection)
responds to info about orientation
complex cell (feature detection)
responds to info about movement
hypercomplex (feature detection)
responds to info about shape
illumination
physical, objective measurement that is simply amount of light falling on surface
brightness
subjective impression of intensity of light stimulus
dark adaptation
when you first walk into theater, it’s dark, and you adapt to dark light
caused by regeneration of rhodopsin
rhodopsin
photochemical in rods; decomposes when molecule absorbs photon of light
what is rhodopsin made of?
retinal & opsin
simultaneous brightness contrast
target area of particular luminance appears brighter when surrounded by darker stimulus than when surrounded by lighter stimulus
lateral inhibition
adjacent retinal cells inhibit one another; sharpens & highlights borders between light & dark areas
color perception
related to wavelength of light entering eye
subtractive color mixture
happens when you mix pigments
additive color mixing
has to do with lights
primary colors: blue, green, red (NOT yellow)
Young-Helmhotz / trichromatic theory
3 types of color receptors: red, blue, green
correct
Hering / opponent process theory
3 opposing pairs: red-green, blue-yellow, black-white
incorrect, but does apply to LGN cells
afterimage
visual sensation that appears after prolonged or intense exposure to stimulus
- used to support Hering’s theory
interposition / overlap
one object (A) covers or overlaps with object (B)
relative size
as an object gets farther away, its image on the retina gets smaller
linear perspecive
convergence of parallel lines in the distance
lines that are actually parallel appear to converge
texture gradients
variations in perceived surface texture as a function of the distance from the observer
- more distant parts of scene appear to have smaller, more densely packed elements
motion parallax
when observer moves, objects in a stationary environment appear to move relative to distance from observer
kinetic depth effect
when object rather than perceiver moves, motion of that object gives us cues about relative depth of parts of object
binocular disparity / stereopsis
each eye sees slightly different scene; when brain combines scenes, we get a perception of depth
binocular depth clue
requires use of two eyes
monocular depth clue
requires use of one eye
binocular parallax
degree of disparity between retinal images of eyes due to slight differences in horizontal position
figure
integrated visual experience that stands out at center of attention
ground
background against which figure appears
law of priximity
elements close to one another tend to be perceived as a unit
law of similarity
objects that are similar tend to be grouped together
law of good continuation
elements that appear to follow in the same direction tend to be grouped together
subjective contours
tendency to see incomplete figures as complete
law of pragnanz
perceptual organization will always be as regular, simple, and symmetric as possible
theory of isomorphism (Kohler)
one-to-one correspondence between object in perceptual field & pattern of stimulation in brain
