Chapter 6-Space Perception and Binocular Vision Flashcards
Realism
The external world exists
Positivists
The world depends on the evidence of the senses; it could be hallucination
Euclidian Geometry
Parallel lines remain parallel as they are extended in space
Is the retinal image Euclidian?
No- brain works with non- Euclidian dimensions all the time
Rabbit Visual field :
Prey- who is going to eat me
can see all around and above
Human visual field
Predator- Who am I going to eat
Since eyes at the front can only see in front a little to the sides
Probability summation
- The increased probability of detecting a stimulus from having two or more samples
- since we have two eyes focusing on same thing we can protect one thing (ex food)
Binocular Summation
The combination (or summation) of signals from each eye in ways that make performance on may tasks better with eyes than with either eye alone
Binocular Disparity
The differences between the two retinal images of the same scene
Depth cue
Information about the third dimension (depth) of visual space
Monocular Depth cue
A depth cue that is available even when the world is viewed with one eye alone
-predator and prey can do this
Binocular Depth Cue
A depth cue that relies on information from both eyes
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Occlusion or interposition
A cue to relative depth order in which for example one object partially obstructs the view of another object
Metrical depth cue
A depth cue that provides quantitative information about distance in the third dimension
Nonmetrical depth cue
A depth cue that provides information about the depth order (relative depth but not depth magnitude
Relative size
A comparison of size between items without knowing the absolute size of either one
Relative height
For objects touching the ground those higher in the visual field appear to be farther away in the sky above the horizon objects lower in the visual field appear to be farther away
Texture gradient
A depth cue based on the same geometric fact that items of the same size form smaller closer spaced images the farther away they get
A familiar size
A cue based on knowledge of the typical size of objects
-if you know size of something you can guess distance based on size you see
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 A or B
Absolute metrical depth cue
A depth cue that provides quantifiable information about distance in the third dimension (eg his nose sticks out 4cm infront of his face
Aerial persepective
A depth cue based on the implicit understanding that light is scattered through the atmosphere-(example see blue different blue for sky and mountain)
Linear perspective
Lines that are parallel in three dimensional world will appear to converge in a two-dimensional image as they extend into the distance
Vanishing point
the apparent point at which parallel lines receding in depth converge
Pictorial depth cue
A cue to distance or depth used by artists to depict three dimensional depth in two dimensional pictures
Anamorphosis or anamorphic projection
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 counter the distortion
Motion parallax
images closer to the observer move faster across the visual field than images farther away
Accommodation
The process by which the eye changes its focus (in which the lens gets fatter as the gaze is directed toward the nearer objects )
Convergence
The ability of the two eyes to turn inward often used to focus on nearer objects
Divergence
The ability of the two eyes to tune outward often used to focus on to farther objects
Shadow cues
- shadows give us
stereoscopic vision geometry
-the way to get all the info from motion paralax without having to move : Two eyes see two different position
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
Horopter (vieth-Müller circle)
the location of objects whose images fall on geometrically corresponding points in the two retinas
-The location of objects whose images lie on corresponding points
Diplopia
Double vision- if visible in both eyes, stimuli falling outside of panum’s fusional area will apear
Panum’s fusional area
The region of space in front of and 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 the horopter –>
uncrossed disparity
- the sign of disparity created by objects behind the plane of fixation
Stereoscope
A device for presenting one mage to one eye and another image to the other eye
free fusion
The technique of converging (crossing) or diverging (uncrossing) the eyes in order to view a stereogram without a steroscope
Stereoblindness
An inability to make use of binocular disparity as a depth cue
Random Dot stereogram (RDS)
A stereogram made of a large number of randomly placed dots
cyclopean
referring to stimuli that are defined by binocular disparity alone
Uniqueness constraint-
The observation that a feature in the world is represented exactly once in each retinal image
Continuity constraint
The observation that except at the edges of objects neighboring points in the world lie at similar distances from the viewer
The Bayesian Approach
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
Ames room
-perspective room- looks like 90* angles but not 90* angles
Binocular Rivalry
The competition of two eyes for control of visual perception
Strabismus
A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye and on the non foveal area of the other eye
Esotropia
Strabismus in which one eye deviates inward
Exotropia
Strabismus in which one eye deviates outwards
Suppression
In vision, the inhibition of an unwanted image
Amblyopia
Permanent suppression of one eyes input in visual cortex
