absorption spectrum
A plot of the amount of light absorbed by a visual pigment versus the wavelength of the light.
accommodation
in vision bringing objects located at different distances into focus by changing the shape of the lens
axial myopia
the eyeball is too long so images of faraway objects are not focused sharply, so objects look blurred.
bipolar cells
eye neurons that receive information from the retinal cells and distribute information to the ganglion cells/ , In the retina, the specialized neurons that connect the rods and cones with the ganglion cells
blind spot
The point at which the optic nerve leaves the eye where there are no receptor cells
cone
cone-shaped receptors in the retina that are primarily responsible for vision in high levels of illumination and for colour vision and detail vision/ works best in bright light; greatest density in the fovea
cornea
the transparent focusing element of the eye that is the 1st structure through which light passes as it enters the eye. It is the eyes major focusing element.
dark adaptation
visual adaptation that occurs in the dark, during which the sensitivity to light increases. The increase in sensitivity is associated with regeneration of the rod and cone visual pigments/ , The process in which the eyes become more sensitive to light in
dark adaptation curve
The function that traces the time course of the increase in visual sensitivity that occurs during dark adaptation./A plot of how visual sensitivity changes in the dark, beginning with when the lights are extinguished.
dark-adapted sensitivity
the sensitivity of the eye after it has completely adapted to the dark
electromagnetic spectrum
The entire spectrum of radiation ranging in wavelength from less than a nanometer to more than a kilometer/ visible light is a narrow band within this
far point
the distance at which the spot of light becomes focused on the retina
fovea
a small area in the human retina that contains only cone receptors. It is located on the line of sight, so that when a person looks at an object, the center of its image falls on the ______.
grandmother cell
A hypothesized type of neuron that responds only to a very specific stimulus, such as a person's grandmother.
ganglion cell
A neuron in the retina that receives input from bipolar and amacrine cells. The axons of the ganglion cells travel out of the eye in the optic nerve.
Hermann grid
A geometrical display that results in the illusion of dark areas at the intersection of two white "corridors." This perception can be explained by lateral inhibition.
lateral inhibition
inhibition that is transmitted laterally across a nerve circuit. In the retina, it is transmitted by the horizontal and amacrine cells.
horizontal cell
a neuron that transmits signals laterally across the retina. It synapses with receptors and bipolar cells.
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
hue
the quality of a color as determined by its dominant wavelength/ the experience of a chromatic colour such as green, red, yellow, or blue or its combinations.
hyperopia
A condition in which visual images are routinely focused behind rather than on the retina; farsightedness.
illusory motion
perception of motion when there actually is none
lightness
Perception of reflectance. Usually objects with high reflectance are perceived as white and objects with low reflectance are perceived as gray or black.
lightness constancy
People perceive lightness/darkness of an object the same regardless of the illumination of the space in which the object is viewed.
rod-cone break
The point on the dark adaptation curve at which vision shifts from cone vision to rod vision.
lens
A clear piece of curved glass or plastic that bends passing light to focus or spread the light rays/ the transparent focusing element of the eye through which light passes after passing through the cornea and the aqueous humour. Its change in shape to foc
light-adapted sensitivity
the sensitivity of the eye when in the light-adapted state. Usually taken as the starting point for the dark adaptation curve because it is the sensitivity of the eye just before the lights are turned off/ , the observer indicates his or her sensitivity b
macular degeneration
a clinical condition that cause degeneration of the macula, an area of the retina that includes the fovea and a small surrounding area.
monochromatic light
light that contains only a single wavelength
neural convergence
synapsing of a number of neurons onto one neuron/ rods and cones send signals vertically through the ganglion cells, horizontally through the amarcine cells, vertically through the bipolar cells and then horizontally through the horizontal cells.
neural circuit
a number of neurons that are connected by synapses
myopia
A condition in which visual images are focused in front of rather than on the retina; nearsightedness.
peripheral retina
all of the retina except the fovea and a small area surrounding the fovea
near point
distance at which your lens can no longer adjust to bring close objects into focus
pupil
opening through which light reflected from objects in the environment enters the eye
law of proximity
The Gestalt principle that we tend to group objects together when they are near each other.
ponzo illusion
An illusion of size in which two objects of equal size that are positioned between two converging lines appear to be different in size. Also called the railroad track illusion.
presbyopia
the inability of the eye to accommodate due to a hardening of the lens and a weakening of the ciliary muscles.
reaction time
the time between presentation of a stimulus and an observers or listeners response to the stimulus. Measure of speed of processing.
refractive myopia
the cornea and/or the lens bends the light too much so images of faraway objects are not focused sharply, so objects look blurred./
retina
a complex network of cells that covers the inside back of the eye. These cells include the receptors, which generate an electrical signal in response to light, as well as the horizontal, bipolar, amacrine, and ganglion cells.
retinal disparity
a binocular cue for perceiving depth; by comparing images from the two eyeballs, the brain computes distance - the greater the disparity (difference) between the two images, the close the object
Each eye is a different camera- the more disparity, the item
rod
Located in the periphery of the retina, these are sensory receptors for vision that work best in reduced illumination, and only allow perception of achromatic colors, low sensitivity to detail and are not involved in color vision. The brain doesn't receiv
spectral sensitivity
an observer's sensitivity to light at each wavelength across the visible spectrum
visual acuity
Sharpness of vision/ ability to resolve small details
texture gradient
A monocular cue for perceiving depth; a gradual change from a coarse distinct texture to a fine, indistinct texture signals increasing distance. objects far away appear smaller and more densely packed
stereopsis
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./
, The ability to perceive depth visually in three dimensions
visible light
Electromagnetic radiation that can be seen with the unaided eye
visual pigment
light-sensitive pigments that react to light and trigger electrical signals. Found in the rods and cones outer segments
wavelength
for light energy, the distance between one peak of a light wave and the next peak.
selective transmission
When some wavelengths pass through visually transparent objects or substances and others do not. Is associated with the perception of chromatic colour.
in the case that things are transparent such as liquids, plastics, and glass, chromatic colour is creat
law of similarity
A law of perceptual organization that states that similar things appear to be grouped together. i.e. circles of the same color are grouped together.
size constancy
Perception of an object as the same size regardless of the distance from which it is viewed
purkinje shift
The shift from cone vision to rod vision that causes this enhanced perception of short wavelengths during dark adaptation.
cognition
the processes or faculties which knowledge is acquires and manipulated. It is not trivial, it is active. All the mental activities associated with thinking, knowing, remembering, and communicating.
stroop test
a standard measure of effortful control over responses, requiring participants to identify the color of a word (which may name a different color)
emmerts law
size of an object's retinal image varies inversely with the distance of the object, R=S/D *K, R= retinal visual angle, S=size of object, D=distance of object, K=constant/ ,
Perceived size= retinal size x apparent distance
you perceive the size the same if
shape constancy
the tendency to interpret the shape of an object as being constant, even when its shape changes on the retina
color constancy
Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object
monocular cues
Depth cues that require the use of only one eye.
pictorial cues
A monocular depth cue, can be represented pictorially on a two-dimensional surface,
Patterns that can be represented on a flat surface in order to create a sense of a three-dimensional object or scene.
interposition
Also called occlusion, it refers to the cue for depth perception when one object (A) covers or overlaps another object (B), and we see object (A) as being in front.
attached shadow
A shadow that directly defines a form, shadow that is on the object itself--it cannot be seen independent of object.
Gives information on form
cast shadow
The shadow thrown by a form onto an adjacent or nearby surface in a direction away from the light source.
Relative distance information
Information on light source
retinal object size
a smaller retinal size means the figure is farther away.
relative size
depth cue: If two objects are similar in size, we perceive the one that casts a smaller image to be farther away.
AKA familiarity
Previous knowledge on the real size of the object, assists us in judging its distance from us.
line perspective
is the method of using lines to show the illusion of depth in a picture.
parallel lines meet at infinity
, parallel lines receding into the distance seem to converge until they meet at a point on the horizon line where they disappear. this point is known
detailed perspective
dense lines/ circles are farther away from the observer
height in the plane
depth cue: Objects closer to the horizon are perceived to be more distant than ones below or above the horizon.
movement cues
objects in our focus will not change their position on the retina. Object closer- will "move" in the other direction (fly by)
Objects farther= will "move" with us in the same direction
binocular cues
think of as biological cues. , Depth cues, such as retinal disparity and convergence, that depend on the use of two eyes
convergence
A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object. The greater the inward strain, the closer the object.
divergence
Ability to maintain focus as an object moves away from you; eyes move laterally away from nose.
Angles between eyes varies with fixation distance
perception
the final product of processing. We do not see the size of an object, its distance, colour, or shape as they are registered on the retina. ,
A person's cognitive (mental) interpretation of events.
motion parallax
a depth cue in which the relative movement of elements in a scene gives depth information when the observer moves relative to the scene
, As we move, objects close to us glide rapidly past, distant objects appear to move more slowly. Far objects move less
likelihood principle
we perceive the object that is most likely to have caused the pattern of stimuli we have received. Proposed by Helmholtz.
holistic
Concerning the whole rather than the parts
perceive the shape as a single _____ shape before perceiving its parts
analytic
perceive the parts of the shape and in light of them - perceive the whole shape.
geons
perceptual building blocks that can be combined to create objects
, Different three dimensional shapes that combine to form three dimensional patterns
recognition by component theory
The idea proposed by Biederman that people recognize objects perceptually via smaller components called geons.
gestalt
A school of psychology that believes individuals perceive objects and patterns as whole units and that the whole is more than the sum of its parts. They believed that behavior, perception, and all elements of the self must be viewed as a whole.
, An organ
mach bands
an illusion due to the bands adjacent to each other; our visual system enhances the edges and makes it look stronger than they actually are within a band.
oculomotor cues
created by convergence, divergence and accommodation. cues based on our ability to sense the position of our eyes and the tension in our eye muscles.
reflectance edge
an edge between two areas where the reflectance of two surfaces changes
illumination edge
The border between two areas created by different light intensities in the two areas.
figure-ground segregation
When we see a separate object, it is usually seen as a figure that stands out from its background, which is called the ground.
perceptual segregation
The perceptual separation of one object from another.
reversible figure-ground
A pattern that's figure and ground can be alternately perceived. i.e. vase/two faces.
border ownership
When two areas share a border, as occurs in figure-ground displays, the border is usually perceived as belonging to the figure.
laws of perceptual organisation
The principles identified by Gestalt psychologists that describe the ways in which the brain groups bits of sensory stimulation into meaningful wholes or patterns.
law of pragnaz
minimum principle of perception; states that we perceive the simplest organization of information
a gestalt law of perceptual organisation that states that every stimulus pattern is seen in such a way that the resulting structure is as simple as possible.
law of familiarity
things that form patterns that are familiar or meaningful are likely to be grouped together
principle of synchrony
visual events that occur at the same time are perceived as belonging together
law of good continuation
From Gestalt Psychology, it is the tendency for elements appearing to follow in the same direction (such as a straight line or a simple curve) to be grouped together.
heuristics
A simple thinking strategy that often allows us to make judgment and solve problems efficiently; usually speedier, but more error-prone than algorithms
algorithm
A methodical, logical rule or procedure that guarantees solving a particular problem.
accidental viewpoint
A viewpoint relative to an object that results in perception of an accidental (or rarely encountered) property of the object. For example, although three sides of a solid cube are visible from most viewpoints, an accidental property�seeing only one side o
trichromatic theory of colour vision
The theory that the sensation of color results because cones in the retina are especially sensitive to red light (long wave-lengths), green light (medium wavelengths), or blue light (short wavelengths).
apparent distance theory
Near the horizon it is viewed across the filled space of terrain which holds depth information. In the sky there is little depth information.
angular size contrast theory
objects appear smaller when surrounded by larger objects, and larger when surrounded by smaller objects
, According to the ________ theory of moon illusion, the overhead moon appears smaller when it is surrounded by a large amount of sky.
conflicting cues theory
Our perception of line length depends on (1) The actual length of the lines (2) the overall length of the figure
misapplied size constancy scaling
A principle, proposed by Richard Gregory, that when mechanisms that help maintain size constancy in the three-dimensional world are applied to two-dimensional pictures, an illusion of size sometimes results.
additive color mixture
A mixture of lights. If light A and light B are both reflected from a surface to the eye, in the perception of color the effects of those two lights add together
subtractive color mixture
The process of mixing pigments, each of which absorbs some wavelengths of light and reflects others
colours of objects
largely determined by the wavelengths of light that are reflected from the objects into our eyes.
reflectance curves
Plots of the percentage of light reflected verses wavelength for a number of objects.
chromatic colors
the hues-colors such as blue, green, and yellow
selective reflection
When an object reflects some wavelengths of the spectrum more than others. Characteristic of chromatic colours.
achromatic color
A color not found in the visible spectrum, which is a neutral color such as white, black or gray
principle of common region
elements that are within the same region of space appear to be grouped together
principle of uniform connectedness
A principle of perceptual organization that states that a connected region of visual proper- ties, such as lightness, color, texture, or motion, is perceived as a single unit
law of common fate
The Gestalt principle that we tend to group similar objects together that share a common motion or destination
apparent movement
The perception of movement produced by stimuli that are stationary but are presented first at one positions and then, at an appropriate time interval, presented at a different position.
belongingess
an areas appearance influenced by the part of the surroundings to which the area appears to belong to. Explains "Whites Illusion.
absolute disparity
Indicates how far an image is from the horopter. This changes every time the observer changes where he/she is looking.
Is important because it provides information about the distances of objects.
angle of disparity
The visual angle between the images of an object on the two retinas. When images of an object fall on corresponding points, the angle of disparity is zero. When images fall on noncorresponding points, the angle of disparity indicates the degree of non cor
non-accidental properties
whether edges are straight or curved - not an accident of your particular viewpoint