Sensation And Perception Ch. 6 Space Perception And Binocular Vision

Front 1

absolute disparity

Back 1

A difference in the actual retinal coordinates in the left and right eyes of the image of a feature in the visual scene. Compare relative disparity.

Front 2

absolute metrical depth cue

Back 2

A cue to depth that provides absolute information about the distance in the third dimension (e.g., his nose sticks out 4 cm in front of his face). Compare relative metrical depth cue.

Front 3

accommodation

Back 3

The process by which the eye changes its focus (in which the lens gets fatter as you direct your gaze toward nearer objects).

Front 4

aerial perspective

Back 4

A depth cue that is based on the implicit understanding that light is scattered by the atmosphere. More light is scattered when you look through more atmosphere. Thus, more distant objects are subject to more scatter and appear fainter, bluer, and less distinct. Also called “haze.”

Front 5

Bayesian approach

Back 5

A statistical model based on Reverend Thomas Bayes’ insight that prior knowledge could influence your estimates of the probability of a current event.

Front 6

binocular disparity

Back 6

The differences between the two retinal images of the same scene. Disparity is the basis for stereopsis, a vivid perception of the three-dimensionality of the world that is not available with monocular vision.

Front 7

binocular rivalry

Back 7

The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes.

Front 8

binocular summation

Back 8

An advantage in detecting a stimulus that is afforded by having two eyes rather than just one.

Front 9

continuity constraint

Back 9

In stereopsis, the observation that, except at the edges of objects, neighboring points in the world lie at similar distances from the viewer. This is one of several constraints that have been proposed to help solve the correspondence problem.

Front 10

convergence

Back 10

The ability of the two eyes to turn inward, often used in order to place the two images of a feature in the world on corresponding locations in the two retinal images (typically on the fovea of each eye). Convergence reduces the disparity of that feature to zero (or nearly zero). Compare divergence.

Front 11

correspondence problem (binocular)

Back 11

The problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye. The problem is particularly vexing when the images consist of thousands of similar features like dots in random dot stereo­grams.

Front 12

corresponding retinal points

Back 12

A geometric concept stating that points on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye. The two foveas are also corresponding points. Compare disparate points.

Front 13

crossed disparity

Back 13

The sign of disparity created by objects in front of the plane of fixation (the horopter). The term crossed is used because images of objects that are located in front of the horopter will appear to be displaced to the left in the right eye, and to the right in the left eye. Compare uncrossed disparity.

Front 14

cyclopean

Back 14

Referring to stimuli that are defined by binocular disparity alone. Named after the one-eyed Cyclops of Homer’s Odyssey.

Front 15

depth cues

Back 15

Information about the third dimension (depth) of visual space. Depth cues may be monocular or binocular.

Front 16

diplopia

Back 16

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

Front 17

divergence

Back 17

The ability of the two eyes to turn outward, often used in order to place the two images of a feature in the world on corresponding locations in the two retinal images (typically on the fovea of each eye). Divergence reduces the disparity of that feature to zero (or nearly zero). Compare convergence.

Front 18

Euclidean

Back 18

Referring to the geometry of the world, so named in honor of Euclid, the ancient Greek geometer of the third century BCE. In Euclidean geometry, parallel lines remain parallel as they are extended in space, objects maintain the same size and shape as they move around in space, the internal angles of a triangle always add to 180°, and so forth.

Front 19

familiar size

Back 19

A depth cue based on knowledge of the typical size of objects like humans or pennies.

Front 20

free fusion

Back 20

The technique of converging (crossing) or diverging the eyes in order to view a stereogram without a stereoscope.

Front 21

horopter

Back 21

The location of objects whose images lie on corresponding points. The surface of zero disparity. See also Vieth–Müller circle.

Front 22

linear perspective

Back 22

A depth cue based on the fact that lines that are parallel in the three-dimensional world will appear to converge in a two-dimensional image.

Front 23

metrical depth cue

Back 23

A depth cue that provides quantitative information about distance in the third dimension. Compare nonmetrical depth cue.

Front 24

monocular

Back 24

With one eye. Compare binocular.

Front 25

monocular depth cue

Back 25

A depth cue that is available even when the world is viewed with one eye alone. Compare binocular depth cue.

Front 26

motion parallax

Back 26

An important cue to depth that is based on head movement. The geometric information obtained from an eye in two different positions at two different times is similar to the information from two eyes in different positions in the head at the same time. See stereopsis.

Front 27

nonmetrical depth cue

Back 27

A depth cue that provides information about the depth order (relative depth) but not depth magnitude (e.g., his nose is in front of his face). Compare metrical depth cue.

Front 28

occlusion

Back 28

A cue to relative depth order when, for example, one object obstructs the view of part of another object.

Front 29

Panum’s fusional area

Back 29

The region of space, in front of and behind the horopter, within which binocular single vision is possible. See also diplopia.

Front 30

pictorial depth cue

Back 30

A cue to distance or depth used by artists to depict three-dimensional depth in two-dimensional pictures. See monocular depth cue.

Front 31

positivism

Back 31

A philosophical position arguing that all you really have to go on is the evidence of your senses, so the world might be nothing more than an elaborate hallucination. Compare realism.

Front 32

random dot stereogram (RDS)

Back 32

A stereogram made of a large number (often in the thousands) of randomly placed dots. The random dot stereogram contains no monocular cues to depth. Stimuli visible stereoscopically in random dot stereograms are cyclopean stimuli.

Front 33

realism

Back 33

A philosophical position arguing that there is a real world to sense. Compare positivism.

Front 34

relative disparity

Back 34

The difference in absolute disparities of two elements in the visual scene. Compare absolute disparity.

Front 35

relative height

Back 35

As a depth cue, the observation that objects at different distances from the viewer on the ground plane will form images at different heights in the retinal image. Objects farther away will be seen as higher in the image.

Front 36

relative metrical depth cue

Back 36

A depth cue that could specify, for example, that object A was twice as far away as object B without providing information about the absolute distance to either A or B.Compare absolute metrical depth cue.

Front 37

relative size

Back 37

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

Front 38

stereoblindness

Back 38

An inability to make use of binocular disparity as a depth cue. This term is typically used to describe individuals with vision in both eyes. Someone who loses one (or both) eyes is not typically described as “stereoblind.”

Front 39

stereopsis

Back 39

The ability to use binocular disparity as a cue to depth. Compare monocular.

Front 40

stereoscope

Back 40

A device for presenting one image to one eye and another image to the other eye, thereby creating a single, three-dimensional image.

Front 41

strabismus

Back 41

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

Front 42

texture gradient

Back 42

A depth cue based on the geometric fact that items of the same size form smaller images when they are farther away. Thus, an array of items that change in size across the image will appear to form a surface in depth.

Front 43

uncrossed disparity

Back 43

The sign of disparity created by objects behind the plane of fixation (the horopter). The term uncrossed is used because images of objects that are located behind the horopter will appear to be displaced to the right in the right eye, and to the left in the left eye. Compare crossed disparity.

Front 44

uniqueness constraint

Back 44

In stereopsis, the observation that a feature in the world will be represented exactly once in each retinal image. This constraint simplifies the correspondence problem.

Front 45

vanishing point

Back 45

The apparent point at which parallel lines receding in depth converge. See also Euclidean and linear perspective.

Front 46

Vieth–Müller circle

Back 46

The location of objects whose images fall on geometrically corresponding points in the two retinas. If life were simple, this circle would be the horopter, but life is not simple.