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Exam 3 Terms

Terms in this set (64)

Cerebral achromatopsia
color blindness
Selective reflection
when an object reflects some wavelengths of the spectrum more than others
Chromatic colors
colors with hue
Achromatic colors
colors without hue; black, gray, and white
Selective transmission
when some wavelengths pass through visually transparent objects or substances and others do not
Wavelengths vs. Perceived Color?
-Short
-Medium
-Medium and Long
-Long
-Long, Medium, and Short
-blue
-green
-yellow
-red
-white
Subtractive color mixing
the creation of colors that occurs when paints of different colors are mixed together
Additive color mixture
the creation of colors that occurs when lights of different colors are superimposed
Spectral colors
colors that appear in the visible spectrum; ROYGBIV
Non-spectral colors
colors that do not appear in the spectrum because they are mixtures of other colors; ex. Magenta
Hue
experience of chromatic colors
Saturation
determined by the amount of white that has been added to a particular hue
Value
the light-to-dark dimension of color
Trichromatic theory of color vision
a theory proposing that our perception of color is determined by the ratio of activity in three receptor mechanisms with different spectral sensitivities
Researchers found pigments that responded maximally to: short WL, medium WL, and long WL. What were the numbers?
short - 419nm
medium - 531nm
long - 558nm
Metamers
two lights that have different WL distributions but are perceptually identical
Metamerism
the situation in which two physically different stimuli are perceptually identical; in vision, this refers to two lights with different WL distributions that are perceived as having the same color
Monochromat?
Dichromat?
Trichromat?
one type of visual pigment
two types of visual pigment
three types of visual pigment
Opponent process theory of color vision
a theory proposed that stated that color vision is caused by opposing responses generated by blue and yellow, and red and green
Monochromats have:
-a very rare hereditary condition
-only rods, no functioning cones (poor visual acuity and high sensitivity to bright light)
-ability to perceive only in white, gray, and black tones
-true color blindness
Type of Dichromatism: Protanopia
-affects 1% of males, .02% of females
-missing long WL pigment
-see short WL as blue, and as WL increase, blue becomes less and less saturated until see gray (neutral point -492nm)
-above neutral point, they see yellow
Type of Dichromatism: Deuteranopia
-affects 1% males, .01% of females
-missing medium WL pigment
-perceives blue at short WL, sees yellow at long WL
-neutral point of 498nm
Type of Dichromatism: Tritanopia
-affects .002% males, .001% females
-missing short WL pigment
-sees blue at short WL, red at long WL, and a neutral point at 570nm
Akinetopsia
blindness to motion
Real motion
an object is physically moving
Illusory Motion
apparent motion (stationary stimuli are presented in slightly different locations; basis of movement in movies and tv)
Induced motion
movement of one object results in the perception of movement in another object
Motion aftereffect
an illusion that occurs after a person views a moving stimulus and then sees movement in the opposite direction when viewing a stationary stimulus immediately after
Waterfall Illusion
an aftereffect of movement that occurs after viewing a stimulus moving in one direction, such as a waterfall. Viewing the waterfall makes other objects appear to move in the opposite direction
GIbson's Ecological Approach
stated that information is directly available in the environment for perception
Optic Array
structure created by surfaces, textures, and contours, which change as the observer moves through the environment
Local disturbance in the optic array
objects in stationary backgrounds become covered and uncovered
Global optic flow
overall movement of optic array; indicates that observer is moving (via body or scanning with eyes) and not the environment
Reichardt detector
a neural circuit in which signals caused by movement of a stimulus across the receptors are processed by a delay unit and an output unit so that signals are generated by movement in one direction but not in the opposite direction
Delay unit
delays the transmission of nerve impulses as they travel from the receptors toward the brain
Output unit
compares signals received from 2 or more neurons
Corollary Discharge theory
explains motion perception as being determined both by movement of the image on the retina and by signals that indicate movement of eyes
IDS, MS, CDS?
Image displacement signal: movement of image stimulating receptors across the retina

Motor signal: signal sent to eyes to move eye muscles

Corollary discharge signal: copy of MS, that instead of going to eye muscles, goes to different place in brain
Transcranial magnetic stimulation
a procedure that temporarily disrupts the normal functioning of neurons by applying electromagnetic pulses; under TMS, participants had trouble determining the direction in which a random pattern of dots was moving (temporary form of akinetopsia)
Aperture problem
occurs when only a portion of a moving stimulus can be seen, as when the stimulus is viewed through a narrow aperture or through the "field of view" of a neuron's receptive field. This can result in misleading information about the direction in which the stimulus is moving
Cue approach to depth perception
focuses on information in the retinal image that is correlated with depth in the scene; ex. occlusion
Occulomotor cues
depth cues that are based on sensing the position of the eyes and muscle tension
Two types of occulomotor cues:
convergence - the inward movement of the eyes when we focus on nearby objects

accommodation - the shape of the lens changes when we focus on objects at different distances
Monocular cues
depth cues that work with the use of only one eye; such as, overlap, relative size and height, familiar size, linear perspective, movement parallax, and accommodation
Three types of monocular cues
accommodation

pictorial cues - depth info can be depicted in 2-D pictures

movement cues - depth info created by movement
7 Pictorial Cues:
1. Occlusion
2. Relative height
3. Relative size
4. Perspective convergence
5. Atmospheric perspective
6. Texture gradient
7. Shadows
Occulsion
when one object partially covers another
Relative Height
-objects below the horizon that are higher in the field of vision are more distant
-for objects above the horizon, objects lower in the visual field are more distant
Relative Size
when objects are equal size, the closer one will take up more of your visual field
Perspective Convergence
parallel lines appear to come together in the distance
Atmospheric perspective
distant objects are fuzzy and have a blue tint
Texture gradient
equally spaced elements are more closely packed as distance increases
Shadows
indicates where objects are located
Motion-Produced Cue: Motion parallax
close objects in direction of movement glide rapidly past but objects in the distance appear to move slowly
When Monocular Depth Cues are used best:
1. Relative height - we can see where objects touch the ground
2. Shadow - if scene is illuminated at an angle
3. Familiar size - if we have prior knowledge of the objects' size
4. Accommodation and convergence - close range
5. Motion parallax, deletion, and accretion - at close and medium ranges
6. Atmospheric perspective, relative height, texture gradient - long ranges
7. Occlusion, relative size - at the whole range of depth perception
Stereoscopic depth perception
depth perception created by input from both eyes
Strabismus
misalignment of the eyes; in which the visual system suppresses vision in one of the eyes to avoid double vision, so the person sees the world with only one eye at a time
Binocular disparity
difference in the images from two eyes; difference can be described by examining corresponding points on the two retinas
Corresponding points
points on the retina that would overlap if the eyes were superimposed on each other
Noncoreresponding points
two points, on each retina, that would not overlap if the retinas were slid onto each other; also called disparate points
Horopter
an imaginary surface that passes through the point of fixation; images caused by a visual stimulus on this surface fall on corresponding points on the two retinas
Binocular depth cells
cells that respond best to a specific degree of absolute disparity between images on the right and left retinas; a.k.a. "disparity selective cells"
Visual Angle
angle of object relative to an observer's eyes; depends on both the size of the object and the distance from the observer
Size constancy
the perception of an object's size remains relatively constant
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