PSYC 230 EXAM 2

Three steps to color perception

detection, discrimination, appearance

detection

wavelengths of light must be detected

discrimination

we must be able to tell the difference between wavelengths

appearance

assigning wave lengths and letting them stay that way over time

Cone types of photoreceptors

S, M, L (short, medium, long)

photopic

bright enough to stimulate the cone receptors and to saturate the rod receptors

scotopic

bright enough to stimulate the cone but too dim to saturate rods

The problem of univariance

An infinite set of combinations can get the same response from a single type of photoreceptor. One type of photoreceptor cannot make color discriminations based on wavelength

trichromacy

the color of any light is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the three cones

cone-opponent cell

neuron whose output is based on a difference between sets of cones.

color space

three-dimensional space that describes all colors.

RGB color space

Defined by the outputs of short, medium, and long wavelength lights

HSB color space

hue, saturation, brightness

opponent color theory

perception of color is based on the output of three mechanisms, each of them based on an opponency between two colors

Ewald Hering

legal/illegal color combinations. cannot have bluish yellow or reddish green.

unique hue

Any of four colors that can be described with only a single color term: Red, yellow, green, blue

achromatopsia

An inability to perceive colors; caused by damage to the central nervous system

Afterimage/ Negative afterimage

A visual image seen after a stimulus has been removed. Negative is that it is the opposite.

Deuteranope

absence of M cones

Protanope

absence of L cones

Tritanope

absence of S cones

Cultural Relativism

In sensation and perception, the idea that basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment

color contrast

color perception effect in which the color of one region induces the opponent color in a neighboring region

color assimilation

two colors bleed into each other, each taking on some of the chromatic quality of the other

color constancy

tendency of a surface to appear the same color under a fairly wide range of illuminants

synethesia

color as emotion. grapheme.

binocular summation

signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone

binocular disparity

The differences between the two retinal images of the same scene

occlusion

cue to relative depth order in which, for example, one object obstructs the view of part of another object

relative size

comparison of size between items without knowing the absolute size of either one

relative height

Below the horizon, objects higher in the visual

field appear to be farther away.

texture gradient

depth cue based on the geometric fact that items of the same size form smaller images when they are farther away

familiar size

A cue based on knowledge of the typical size of objects

aerial perspective or haze

Thus, more distant objects appear fainter, bluer, and less distinct

linear perspective

Lines that are parallel in the 3D world will appear to converge in a 2D image as they extend into the distance. (looking at a picture of hallway)

pictorial depth cue

cue to distance or depth used by artists to depict three-dimensional depth in two-dimensional pictures

motion parallax

Images closer to the observer move faster across the visual field than images farther away

corresponding retinal points

points on the retina of each eye where the images of a single object are formed are at the same distance from the fovea in each eye

horopter

objects whose images fall on geometrically corresponding points in the two retinas. The surface of zero disparity

panum's fusional area

region of space, in front of and behind the horopter, within which binocular single vision is possible

Diplopia

Double vision. If visible in both eyes, stimuli falling outside of Panum's fusional area will appear diplopic

crossed disparity

objects in front of the plane of the horopter

free fusion

converging/diverging the eyes in order to view a stereogram without a stereoscope

3D movies

each eye receives a slightly different signal

binocular rivalry

The competition between the two eyes for control of visual perception

stereoacuity

A measure of the smallest binocular disparity that can generate a sensation of depth

strabismus

A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye, and on the nonfoveal area of the other (turned) eye

hair cells

Act as mechanoreceptors in each of the 5 vestibular organs.

rotation perception

spinning in the dark is perceived, then seen as slowing down, then seen as stopping.

translation perception

brain remembers and replicates the velocity.

tilt perception

we are very accurate when perceiving tilt angles between 0 and 90 degrees.

sensory integration

combining different sensory signals

Visual-vestibular integration

vection: moving when you are not

autonomic nervous system

The part of the nervous system innervating glands, heart, digestive system, etc., and responsible for regulation of many involuntary actions

motion sickness

Results when there is a disagreement between the motion and orientation signals provided by the semicircular canals, otolith organs, and vision

blood pressure

regulated by vestibulo- autonomic responses