Space Perception and Binocular Vision

Question 1

aerial perspective (or haze)

Answer 1

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

Question 1

dichoptic

Answer 1

Referring to the presentation of two different stimuli, one to each eye.

Question 1

random dot stereogram (RDS)

Answer 1

A stereogram made of a large number (often in the thousands) of randomly placed dots containing no monocular cues to depth.

Question 2

crossed disparity

Answer 2

The sign of disparity created by objects in front of the plane of fixation (the horopter).

Question 3

corresponding retinal points

Answer 3

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.

Question 4

free fusion

Answer 4

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

Question 4

occlusion

Answer 4

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

Question 4

vanishing point

Answer 4

The apparent point at which parallel lines receding in depth converge.

Question 5

relative height

Answer 5

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.

Question 5

suppression

Answer 5

In vision, the inhibition of an unwanted image; occurs frequently in persons with strabismus.

Question 6

texture gradient

Answer 6

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

Question 6

uniqueness constraint

Answer 6

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

Question 8

binocular depth cue

Answer 8

A depth cue that relies on information from both eyes.

Question 8

motion parallax

Answer 8

An important depth cue 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.

Question 9

divergence

Answer 9

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).

Question 10

ideal observer

Answer 10

A theoretical observer with complete access to the best available information and the ability to combine different sources of information in the optimal manner.

Question 10

stereopsis

Answer 10

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

Question 11

linear perspective

Answer 11

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.

Question 11

projective geometry

Answer 11

For purposes of studying perception of the three-dimensional world, the geometry that describes the transformations that occur when the three-dimensional world is projected onto a two-dimensional surface. For example, parallel lines do not converge in the real world, but they do in the two-dimensional projection of that world.

Question 11

realism

Answer 11

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

Question 13

depth cues

Answer 13

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

Question 14

horopter

Answer 14

The location of objects whose images lie on corresponding points. The surface of zero disparity.

Question 15

monocular depth cue

Answer 15

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

Question 15

relative metrical depth cue

Answer 15

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

Question 15

stereoscope

Answer 15

A device for simultaneously presenting one image to one eye and another image to the other eye.

Question 17

exotropia

Answer 17

Strabismus in which one eye deviates outward.

Question 19

binocular rivalry

Answer 19

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

Question 19

stereoblindness

Answer 19

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.

Question 21

convergence

Answer 21

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).

Question 22

tilt aftereffect

Answer 22

The perceptual illusion of tilt, produced by adaptation to a pattern of a given orientation.

Question 24

accommodation

Answer 24

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

Question 25

familiar size

Answer 25

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

Question 27

critical period

Answer 27

A period of time during development when the organism is particularly susceptible to developmental change.

Question 29

correspondence problem

Answer 29

In binocular vision, 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.

Question 31

Euclidean

Answer 31

Referring to the geometry of the world, named in honor of the ancient Greek geometer of the third century BCE. 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 degrees, and so forth.

Question 32

monocular

Answer 32

With one eye.

Question 34

absolute metrical depth cue

Answer 34

A depth cue that provides quantifiable information about distance in the third dimension (e.g., his nose sticks out 4 centimeters in front of his face).

Question 35

metrical depth cue

Answer 35

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

Question 36

Bayesian approach

Answer 36

A way of formalizing the idea that our perception is a combination of the current stimulus and our knowledge about the conditions of the world—what is and is not likely to occur.

Question 37

esotropia

Answer 37

Strabismus in which one eye deviates inward.

Question 38

pictorial depth cue

Answer 38

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

Question 38

Vieth-Müller circle

Answer 38

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.

Question 39

binocular

Answer 39

With two eyes.

Question 40

uncrossed disparity

Answer 40

The sign of disparity created by objects behind the plane of fixation (the horopter).

Question 43

Cyclopean

Answer 43

Referring to stimuli that are defined by binocular disparity alone.

Question 44

binocular summation

Answer 44

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

Question 45

strabismus

Answer 45

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

Question 47

binocular disparity

Answer 47

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.

Question 49

anamorphosis (or anamorphic projection)

Answer 49

Use of the rules of linear perspective to create a two-dimensional image so distorted that it looks correct only when viewed from a special angle or with a mirror that counters the distortion.

Question 50

stereoacuity

Answer 50

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

Question 51

positivism

Answer 51

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

Question 52

Panum’s fusional area

Answer 52

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

Question 53

nonmetrical depth cue

Answer 53

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).

Question 54

diplopia

Answer 54

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

Question 55

continuity constraint

Answer 55

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.

Question 56

relative size

Answer 56

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