a plot showing the percentage of light reflected from an object versus wavelengh
determines activity of the 3 cone types, different wavelength
two lights that have different wavelength distribution but are perceptually identical
a procedure in which observers are asked to match the color in one field by mixing two or more lights in another field.
a person who is completely color blind and therefore sees everything as black white, or shades of gray. can match any wavelength in the spectrum by adjusting the intensity of any other wavelength. usually only have one type of functioning receptors, usually rods
a person who has a form of color deficiency. can match any wavelength in the spectrum by mixing two other wavelengths. deuteranopes, protanopes, and tritanopes are all dichromats.
the wavelength at which a dichromat perceives gray
a person with normal color vision. trichromats can match any wavelength in the spectrum by mixing three other wavelengths in various proportions
a person who needs to mix a minimum of three wavelengths to match any other wavelength in the spectrum but mixes these wavelengths in different proportions from a trichromat.
a person who has a retina in which the only functioning receptors are rods.
principle of univariance
absorption of a photon by a visual pigment molecule causes the same effect no matter what the wavelength
theory of trichromacy
a theory proposing that our perception of color is determined by the ratio of activity in three receptor mechanisms with different spectral sensitivities
proposed by hering, claimed our perception of color is determined by the activity of two opponent mechanisms: a blue-yellow mechanism and a red-green mechanism. the responses to the two colors in each mechanism oppose each other, one being an excitatory response. includes a black-white mechanism, concerned with the perception of brightness
neuron that has an excitatory response to wavelengths in one part of the spectrum and an inhibitory response to wavelengths in the other part of the spectrum.
red/green ----- blue/yellow. cannot imagine a mixture because they are paired opposite ends of spectrum,
the difference in light intensity between two areas.
the effect in which the perception of an objects hue remains constant even when the wavelength distribution of the illumination is changed. approximate color constancy means that our perception of hue usually changes a little when the illumination changes, though not as much as we might expect from the change in the wavelengths of light reaching the eye.
the constancy of our perception of an objects lightness under different intensities of illumination
a black surface looks white when seen by itself but looks black when paired with a different surface. (failure of color constancy)
a principle stating that two areas that reflect different amounts of light will look the same if the ratios of their intensities to the of their surroundings are the same.
prolonged exposure to light in a specific part of the visible spectrum, which adapts receptors that fire to these wavelengths by selectively bleaching a specific visual pigment. one of the mechanisms responsible for color constancy.
depth cue that depends on our ability to sense the position of our eyes and the tension in our eye muscles. accomodation and convergence are both cues
the perception that parallel lines in the distance converge as distance increases
depth cue based on muscular sensations that occur when the eye accommodates to bring objects at different distances into focus. provides information about the distances of nearby objects
depth cue such as overlap relative size relative height, familiar size, linear perspective, movement parallax and accommodation, that works when we use only one eye
depth cue such as overlap, relative height, and relative size, that can be depicted in pictures
depth cue in which one object hides or partially hides another object from view, causing the hidden object to be perceived as being farther away
a depth cue. objects that have bases below the horizon appear to be farther away when they are higher in the field of view. objects that have bases above the horizon appear to be farther away when they are lower in the field of view.
the ratio principle does not account for effect to shadows in 3D situations, illumination cues infer the presence of surface changes, requires both local and global processing of visual scene to correctly see lightness provie info regarding the locations of objects.
when two objects are of equal size, the one that is farther away will take up less of the field of view
our knowledge of an objects actual size sometimes influences our perception of an objects distance
objects that are farther away look more blurred and bluer than objects that are closer because we must look through more air and particles to see them.
the visual pattern formed by a regularly textured surface that extends away from the observer. this pattern provide information for distance because the elements in a texture gradient appear smaller as distance from the observer increases
source of depth info, elements that are qually spaced a in a scene appear to be more closely packed as distance increase, more distant objects appear smaller (relative size) rocky ground
movemetn parallax and deletion and accretion-->occurs when a farther object is covered by a nearer object due to sideways movement(occlusion in motion)
accretion--occurs when the observer moves in the other direction so the farther object is covered, make it so overlapping surfaces appear to move relative to on another, effective for detecting depth at an edge
occurs when we move nearby objects off to the side of our direction of movement appear to glide rapidly past us, but more distant objects appear to move more slowly (driving in a car)
the impression of depth that results from binocular disparity-- the difference in the position of images of the same object on the retinas of the two eyes.
depth cue formed by image falling on non corresponding retinal points, Horopters
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.
corresponding retinal points
the points on each retina that would overlap if one retina were slid on top of the other
crossed and uncrossed disparity
crossed-objects in front of the horopter towards the person
uncrossed- objects in back of the horopter away from the person
a law stating that the size of an afterimage depends on the distance of the surface against which the afterimage is viewed. the farther away the surface, the larger the afterimage appears.
size distance scaling
a hypothesized mechanism that helps maintain size constancy by taking an objects perceived distance into account. S(objects perceived size)R(size of the retinal image)D(objects perceived distance)-- S= RxD
misapplied size constancy scaling
a principle proposed by richard gregory that when mechanism that help maintain size constancy in the 3D world are applied to 2D pictures an illusion of size sometimes results
occurs when the size of an object is perceived to remain the same even when it is viewed from distances
shadowing and visual angel are adjusted. violates S=RxD
a situation in which only a portion of a moving stimulus can be seen, as when the stimulus is viewed through a narrow aperture. this results in misleading information about the direction in which the stimulus is moving.
an illusion of movement that occurs between two objects separated in space when the objects are flashed rapidly on and off, one after another separated by a brief time interval
motion produced by biological organisms. most of the experiments on biological motion have used walking humans with lights attached to their joints and limbs as stimuli
an aftereffect of movement that occurs after viewing a stimulus moving in one direction, such as a waterfall. viewing the waterfall creates other objects to appear to move in the opposite direction.
stationary stimuli appear to move without prior adaptation to moving stimuli (weird hypnotic posters)
corollary discharge theory
according to this theory of motion perception a corollary discharge signal, which is a copy of the signal sent from the motor area to initiate an eye movement, is sent to a structure called the comparotor.
motion after effect
WAterfall illustion, see motion of stationary target after adaptation to a texture moving in a single direction, may be related to adaptation of motion sensitive neurons in area MT, shows intraocular transfer
ecological approach to perception
this approach focuses on studying perception as it occurs in natural settings, particularly emphasizing the role of observer movement.
the flow of stimuli in the environment that occurs when an observer moves relative to the environment. forward movement causes an expanding optic flow, whereas backward movement causes a contracting optic flow.
the visual pattern formed by a regularly textured surface that extends away from the observer. this pattern provides information for distance because the elements in a texture gradient appear smaller as distance from the observer increases.
the information specified by a stimulus pattern that indicates how the stimulus can be used. An example of an affordance would be seeing a chair as something to sit on or a flight of stairs as something to climb.
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