Chapter 6: Space Perception and Binocular Vision Flashcards
realism
A philosophical position arguing that there is a real world to sense
Positivism
A philosophical position arguing that all we really have to go on in the evidence of the senses, so the world might be nothing more than an elaborate hallucination.
Euclidean
Referring to the geometry of the world, so named in honor of Euclid. 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 degree etc…
binocular
with two eyes
binocular summation
The combination of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone.
monocular
with one eye
stereopsis
The ability to use binocular disparity as a cue to depth.
depth cues
information about the third dimension (depth) of visual space. Depth cues may be monocular or binocular.
Monocular depth cue
A depth cue that is available even when the world is viewed with one eye alone.
binocular depth cue
A depth cue that relies on info from both eyes. Stereopsis is the primary example in humans, but convergence and the ability of two eyes to see more of an object than one eye sees are also binocular depth cues.
occlusion
A cue to relative depth order in which, for example, one object obstructs the view of part of another object.
nonmetrical depth cue
A depth cue that provides information about the depth order (relative depth) but not depth magnitude.
metrical depth cue
A depth cue that provides quantitative information about distance in the third dimension
projective geometry
To study 3D world, the geometry that describes the transformations that occur when the 3D world is projected onto a 2D surface. Ex: Parallel lines do not converge in the real world but they do in the 2D projection of that world.
Relative size
A comparison of size between items without knowing the absolute size of either one.
texture gradient
A depth cue based on the geometric fact that items of the same size form smaller images when they are far away. An array of items that changes in size smoothly across the image will appear to form a surface titles in depth.
relative height
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.
familiar size
A depth cue based on knowledge of the typical size of objects like humans or pennies.
relative metrical depth cue
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.
absolute metrical depth cue
A depth cue that provides quantifiable information about distance in the third dimension
Aerial perspective (or haze)
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. 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.
linear perspective
A depth cue based on the face that lines that are parallel in the three dimensional world will appear to converge in a two dimensional image.
vanishing point
The apparent point at which parallel lines receding in depth converge
pictorial depth cue
A cue to distance depth used by artists to depict 3D depth in 2D pictures
anamorphosis (anamorphic projection)
use of the rules of linear perspective to create a 2D image so distorted that it looks correct only when viewed at a special angle or with a mirror that counters the distortion.
motion parallax
An important depth cue that is based on head movement. The geometric info obtained from an eye in two different positions at two different times is similar to the information form two eyes in different position in the head at the same time.
accommodation
The process by which the eye changes its focus (in which lens gets fatter as gaze is directed toward nearer objects)
convergence
The ability of the two eyes to turn inwards, 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).
divergence
The ability of the two eyes to turn outward, often used in order to place the two images of 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).
corresponding retinal points
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.
Vieth-Muller circle
The location of objects whose images fall on geometrically corresponding points in the two retinas.
Horopter
The location of objects whose images lie on corresponding points. The surface of zero disparity.
diplopia
Double vision. If visible in both eyes, stimulu falling outside of Panum’s fusional area will appear diplopic/
Panum’s fusional area
The region of space, in front of an behind the horopter, within which binocular single vision is possible.
crossed disparity
The sign of disparity created by objects in front of the plane of fixation (the horopter). The term crossed is used becasue images of objects located in front of the horopter appear to be displaced to the left in the right eye.
uncrossed disparity
The sign of disparity created by objects behind the plane of fixation (the horopter). The term uncrossed is used because images of objects located behind the horopter will appear to be displaced to the right in the right eye, and to the left in the left eye.
Stereoscope
A device for simultaneously presenting one image to one eye and another image to the other eye. Stereoscopes can be used to present dichoptic stimuli for stereopsis and binocular rivalry.
free fusion
the technique of converging or diverging the eyes in order to view a stereogram without a stereoscope.
stereoblindness
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.
Random dot stereograms (RDSs)
A stereogram made of a large number of randomly placed dots. Random dot sterograms contain no monocular cues to depth. Stimuli visible stereoscopically in random dot sterograms are Cyclopean stimuli.
Cylcopean
Referring to stimuli that are defines by binocular disparity alone.
correspondence problem
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.
uniqueness constraint
In stereopsis, the observation that a feature in the world is represented exactly once in each retinal image. This constraint simplifies the correspondence problem.
continuity constraint
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.
Ideal observer
A theoretical observer with complete access to the best available information and the ability to combine different sources of information in the optimal manner. It can be useful to compare human performance to that of an idea observer.
binocular rivalry
The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes.
Steroacuity
A measure of the smallest binocular disparity that can generate a sensation of depth.
dichoptic
Referring to the presentation of two different stimuli, one to each eye. Different from binocular presentation, which could involve both eyes looking at a single stimulus.
critical period
A period of time during development when the organism is particularly susceptible to developmental change. There are critical period in the development of binocular vision, human language, and so on.
Strabismus
A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye and on a non foveal area of the other (turned) eye.
esotropia
Strabismus in which one eye deviates inwards.
exotropia
Strabismus in which one eye deviates outward.
tilt aftereffect
The perceptual illusion of tilt, produced by adaptation to a pattern of a given orientation
supression
In vision, the inhibition of an unwanted image. Suppression occurs frequently in persons with strabismus.
