Space Perception and Binocular Vision

Question 1

Positivism

Answer 1

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

Question 2

Realism

Answer 2

Argues theres a real world to sense.

Question 3

Looking out at the world

Answer 3

2D with a sense of 3D.

Fine taking in parts, but confused when we look at it as a whole.

Put together contours to form images.

How do we know how far something is?

We use perception to interact with world.

We need to know where things are relative to us, to determine how we will interact with them.

Question 4

3D>2D>3D

Answer 4

Problem of the visual system needs to construct a 3D world based on inverted images on retina of each eye.

Goal of depth perception: to accurately perceive a 3D
world on the basis of two 2D retinal images (one in each
eye).

our retina is not flat( is a curved surface).

2 Retinal images always differ because eyeballs are in a different position on head.

Retinal area occupied by an object gets smaller as an object moves away from eyeball. -If we want to understand a 3D world we have to reconstruct of distorted retinal input.

Angles are often greater.

Challenge: an infinite
number of different 3D
scenes can produce the
same retinal image.

Question 5

Probability Summation

Answer 5

Increased detection probability based on statistical advantage of having two (or more) detectors than one

Question 6

Binocular Summation

Answer 6

Probability summation in vision.
Increased detection because of two eyes

Question 7

Pictorial depth cue

Answer 7

A cue to distance or depth used by artists to depict 3D depth in 2D pictures

Trick to depict depth in their painting

Question 8

Monocular depth cue

Answer 8

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

patch over or damaged

Question 9

Binocular depth cue

Answer 9

a depth cue that relies on
information from both eyes

pick up more information from environment

Eyes let us see more of the world– Especially true for animals that have lateral ones. ie/ rabbit. Good for animals of prey

Humans have frontal eyes

Ie/ stereopsis

Question 10

Oculomotor Depth Cues

Answer 10

Cues that are based on
feedback from the oculomotor muscles controlling the shape of the lens and the position of the eyes

The way the eyes move to get a clear image.

Where the eye are actually moving to get info on fovea, Muscle focused;
Accommodation (lens).
Convergence/Divergence.

Question 11

Accommodation

Answer 11

the process by which the eye changes its focus (lens changes its shape).

Contraction of ciliary muscles for near objects (lens gets fatter)–lens more round, bending to get focus on back of eye.

Relaxation of ciliary muscles for far objects.-flatter lens.

Only provides depth information for objects <2m away

Lens has a limit for how much it can change shape.

Question 12

Convergence

Answer 12

the ability of the two eyes to turn inward, often used to focus on nearer objects

Binocular cue–so need to compare. with one eye could just be looking to the side.

are eyes turning inward or outward.

Question 13

Divergence

Answer 13

The ability of the two eyes to turn outward, often used to focus on farther objects

Binocular cue–so need to compare. with one eye could just be looking to the side.

are eyes turning inward or outward.

Question 14

static monocular depth cue

Answer 14

Static monocular depth cues: cues that provide
information abut depth on the basis of:

Position of objects in the retinal image,
Occlusion.
Relative height.
Size of objects in the retinal image.
Relative size.
Familiar size.
The effects of lighting in the retinal image.
Shadows/Shading.
Aerial (atmospheric) perspective.

Question 15

Non metrical depth cue

Answer 15

a depth cue that provides info about the depth cue order (relative depth) but not depth magnitude (nose is in front of his face).

misleading only in case of accidental viewpoints.

Question 16

Metrical depth cue

Answer 16

a depth cue that provides quantitative info about distance in 3rd dimension.

Question 17

Familiar size

Answer 17

a cue based on knowledge of the typical size of objects.-what size ought to be

often works in conjunction with the cue of relative size.

Question 18

Relative metrical depth cue

Answer 18

Could specify that object A is twice as far away as object B without providing info about the absolute distance to either A or B

relative sight and high do not tells us the exact distance to/between objects.

Question 19

Absolute metrical depth cue

Answer 19

Provides quantifiable info about distance in the 3D

familiar size

Question 20

Projective geometry

Answer 20

Geometry that describes the transformations that occur when 3D world is projected onto a 2D surface.

Ie/ parallel lines do not converge in the real world, but they do in 2D projection of that world.

Question 21

Aerial (or atmospheric) perspective. or haze

Answer 21

a depth cue based on the implicit understanding that light is scattered by the atmosphere.

Short wavelengths (blue) are scattered more than medium and long wavelengths. Why the sky looks blue.

More light is scattered when we look through more atmosphere

thus, more distant objects appear fainter, bluer, and less distinct.

contours become less distinct as we get further away.

(Monocular depth cues)

Question 22

Linear perspective

Answer 22

Lines that are parallel in the three-dimensional world will appear to converge in a two-dimensional image as they extend into the distance

(Monocular depth cues)

Question 23

Vanishing point

Answer 23

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

(Monocular depth cues)

Question 24

Relative height

Answer 24

(“height in plane”, “proximity to horizon”):

Objects touching the ground: higher = farther

Objects in the sky (above horizon): lower = farther

Objects will be higher in the visual field if they are more distant.

Higher it is the further away from ground plane.

but closer clouds in sky plane.
Closer=Higher

Question 25

Size-distance relation

Answer 25

Size-distance relation: the farther away an object is from the observer, the smaller is its retinal image

Question 26

Relative size

Answer 26

A comparison of size between items without knowing the absolute size of either one. all things being equal, we assume that smaller objects are further away from us than larger objects.

Question 27

Texture gradient

Answer 27

a depth cue based on the geometric fact that items of the same size form smaller, closer spaced images the farther away they get. Result from a combination of the cues of relative size and relative height. as you go up in image. Space gets closer together as you get further away. (Monocular depth cues)

Question 28

▪ Anamorphosis (or anamorphic projection)

Answer 28

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. our ability to cope with distortion is limited. rules of linear perspective are pushed to an extreme. projection of 3D to 2D. (Monocular depth cues)

Question 29

Dynamic monocular depth cues (Monocular depth cues)

Answer 29

cues that provide information abut depth on the basis of motion. Motion parallax. optic flow. Deletion and Accretion. (Monocular depth cues)

Question 30

triangulation

Answer 30

triangle formed by the two eyes and the point they fixate on in the 3D world.

Question 31

Motion parallax

Answer 31

images closer to the observer move faster across the visual field than images farther away. Head movements and any other relative movements between observers and objects reveal motion parallax cues. A triangulation cue Based on head movement-- Allow for seeing multiple viewpoints by moving head. Animals use it for prey to figure out when to attack. Monocular depth cues

Question 32

Optic flow

Answer 32

the changing angular position of points in a perspective image that we experience as we move through the world. The pattern of apparent motion of objects in a visual scene produced by the relative motion between the observer and the scene. Monocular depth cues

Question 33

Deletion

Answer 33

the gradual hiding (occlusion) of an object as it passes behind another one. Object will be further away from you in order far this to happen. Monocular depth cues

Question 34

Accretion

Answer 34

Object will be further away from you in order far this to happen. the gradual revealing (“de-occlusion”) of an object as it emerges from behind another one. Monocular depth cues

Question 35

Binocular Vision

Answer 35

The probability of detecting a stimulus increases with more samples. One of the advantages of having two eyes that face forward. The two retinal images of a 3D world are not the same. Animals with smaller brains extract depth from disparity. Key points; ▪ Horopter is always centered on fixation point. ▪ Objects on the horopter have zero binocular disparity. ▪ Binocular disparity increases as you move away from the horopter. ▪ If closer than the horopter disparity is crossed. ▪ More crossed disparity as the object gets closer. ▪ If further than the horopter disparity is uncrossed. ▪ More uncrossed disparity as the object gets further. In order to perceive depth from brain must know which part of the right retinal image corresponds with which part of the left retinal image input from two must converge onto the same neuron - this convergence doesn't happen until the V1 V1 neurons are binocular; can be excited by either eye

Question 36

V2

Answer 36

Computes depth order based on contour completion and border ownership.

Question 37

Intermediate visual areas (Ie/V4)

Answer 37

Encode depth intervals, based on relative disparities.

Question 38

Higher cortic areas (inferotemporal cortex)

Answer 38

Are involved in representation of complex 3D shape

Question 39

Binocular neurons in VI

Answer 39

are most responsive to absolute disparities Input from two us must converge onto the same neuron--This convergence doesn't happen until the vI vI neurons are binocular; can be excited by either eye

Question 40

Neurons in V2 and many other higher cortical areas

Answer 40

are sensitive to relative disparities Input from two us must converge onto the same neuron--This convergence doesn't happen until the vI vI neurons are binocular; can be excited by either eye

Question 41

Relative diparties

Answer 41

Provide the basis for very fine stereoaculty. VI signals feed into both ventral(more complex) and dorsal streams(control eye movements) The difference in the absolute disparities of two objects.

Question 42

binocular disparity

Answer 42

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. Objects "popping out" Effective up to 200 m Observers are very sensitive to small binocular disparities Input from two us must converge onto the same neuron--This convergence doesn't happen until the vI vI neurons are binocular; can be excited by either eye

Question 43

Middle temporal area

Answer 43

Important in perception of motion. Cells here can signal sign of depth based on motion parallax of shaking your head.

Question 44

Stereoaculty

Answer 44

is a measure of the smallest binocular disparity that can generate a sense of depth. Increased after stereopsis rapidly until adult levels rose from nothing first 4 months to near adult levels by 6 months different from simple acuity that takes years to develop.

Question 45

absolute disparity

Answer 45

the difference in the angular distance of the images of an object from the foveas of the two eyes. Not consciously available ti make perceptual judgments disregarded because convergence noise is common whereas relative disparities are not.

Question 46

Corresponding points

Answer 46

a point on the left retina and a point on the right retina that would coincide if the two retinas were superimposed (e.g., the foveas of the two eyes) if they are at the same distance to the fovea on both sides. tend to have zero binocular disparity. binocular vision

Question 47

Non-corresponding points

Answer 47

a point on the left retina and a point on the right retina that would not coincide if the two retinas were superimposed (e.g., the fovea of one eye and a point 4 mm to the right of the fovea in the other eye) objects significantly closer to or farther away from the surface of zero disparity form images on non corresponding parts of the eyes.- this double vision is known as diplopia. binocular vision.

Question 48

Occlusion

Answer 48

a cue to relative depth order in which, for example, one object partially obstructs the view of another object. gives info about relative position of objects. argues to be most reliable of all depth cues. more powerful depth cue. light needs to come from object to your eye to see it, so if something is blocking/obstructing will reach your eye can be misleading in the care of accidental viewpoints ie/ weirdly fitting puzzle pieces more likely to be the generic view blocking=closer

Question 49

Horopter

Answer 49

the location of objects whose images lie on the corresponding points in the two retinas. The surface of zero disparity Objects on the horopter are seen as single images when viewed with both eyes. The Vieth-Müller circle and the horopter are technically different, but for our purposes you may consider them the same.

Question 50

Panum fusional area

Answer 50

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

Question 51

Diplopia

Answer 51

Double vision If visible in both eyes, stimuli falling outside of Panum’s fusional area will appear diplopic. Objects significantly closer to or farther away from the horopter fall on non-corresponding points in the two eyes and are seen as two images. will be experienced if an adult becomes estropic

Question 52

Crossed disparity

Answer 52

the sign of disparity created by objects in front of the plane of the horopter. (fixation) images in front of the horopter are displaced to the left in the right eye and to the right in the left eye things closer

Question 53

Uncrossed disparity

Answer 53

the sign of disparity created by objects behind the plane of the horopter images behind the horopter are displaced to the right in the right eye and to the left in the left eye created by things further away from you than horropter when we move things to the distance

Question 54

Correspondence problem

Answer 54

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 solving all the time if you have normal binocular vision Particularly vexing in random dot stereograms consisting of many similar features 1) (at least) two options: Object recognition performed separately on the information from each eye, then the objects are matched and disparity is determined (object recognition precedes correspondence matching) 2) The visual system matches the retinal images based on simple features before object recognition (correspondence matching precedes object recognition) ▪ Test: Bela Julesz: random dot stereograms

Question 55

Binocular rivalry

Answer 55

Competition between two eyes for control of visual perception. never completely won by either eye or either stimulus. evident when completely different stimuli are presented to the two eyes. visual system chooses to surpress an image and perceive the other. occurs when corresponding points in the eyes are unrelated

Question 56

dichoptic

Answer 56

presentation of two different stimuli, one to each eye

Question 57

cyclopean

Answer 57

referring to stimuli that are defined by binocular disparity alone.

Question 58

Stereoscope

Answer 58

a device for presenting one image to one eye and another image to the other eye. can be used to present dichoptic stimulus for stereopsis and binocular rivalry. confirmed that the visual system treats binocular disparity as a depth cue. binocular vision

Question 59

Random dot stereogram (RDS)

Answer 59

a stereogram made of a large number of randomly placed dots. to prove that stereopsis might be used to discover objects and surfaces in the world. contain monocular cues to depth and no "objects" thought it might help reveal camouflaged objects. cats have stereopsis. binocular vision

Question 60

Free fusion

Answer 60

the technique of converging (crossing) or diverging (uncrossing) the eyes in order to view a stereogram without a stereoscope. "the poor man's stereoscope" The phenomenon of double vision (diplopia).

Question 61

critical period

Answer 61

a period of time in development when the organism is particularly susceptible to developmental change.

Question 62

Strabismus

Answer 62

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

Question 63

esotropia

Answer 63

strabismus in which one eye deviates inward ("cross eyed")

Question 64

exotropia

Answer 64

strabismus in which one eye deviates outward ("wall eye")

Question 65

Significance of random dot stereograms

Answer 65

If object recognition necessarily precedes correspondence matching, no depth should be seen in a random-dot stereogram, because it does not contain any objects But, since we do see depth in a random-dot stereogram, correspondence matching must precede object recognition

Question 66

Uniqueness constraint

Answer 66

the observation that a feature in the world is represented exactly once in each retinal image binocular vision

Question 67

Continuity constraint

Answer 67

the observation that, except at the edges of objects, neighboring points in the world lie at similar distances from the viewer binocular vision

Question 68

How is stereopsis implemented in the human brain?

Answer 68

Input from two eyes must converge onto the same cell. Many binocular neurons respond best when the retinal images are on corresponding points on the two retinas. neural basis for horopter. Many other binocular neurons respond best when similar images occupy slightly different positions on the retinas of the two eyes. turned to particular disparity.

Question 69

Development of Stereopsis

Answer 69

onset by 3-5 months. adult levels within 6-7 months. abnormal visual experience can disrupt binocular vision:

Question 70

Strabismus

Answer 70

a misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye, and on the nonfoveal area of the other (turned) eye. ▪ Can lead to the suppression of the image from the mis-aligned eye -> stereoblindness

Question 71

Amblyopia

Answer 71

a developmental disorder characterized by reduced spatial vision in an otherwise healthy eye ("lazy eye")

Question 72

tilt aftereffect

Answer 72

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

Question 73

Stereoblindness

Answer 73

an inability to make use of binocular disparity as a depth cue. many people who are stereoblind do not even realize it. Rambrandt was probably stereoblind 3-5 % of population usually a secondary effect of childhood visual disorders

Question 74

Bayesian approach

Answer 74

estimates probability of a current observation. formulating the idea that out perception is a combo of current stimulus. which interpretation seems more likely. automanic. Ie/ pennies are all the same size in our experience.

Question 75

Combining depth cues

Answer 75

depth cues need to be combined 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. The Bayesian approach Prior knowledge can influence our estimates of the probability of an event.

Question 76

Size constancy

Answer 76

Perceived distance distance/depth cues generally, the more depth cues, the more accurate our size constancy ▪ In all of the previous illusions, R was the same and perceived D changed resulting in the illusion. ▪ What if perceived D is kept constant and R changes? the perception of an object as having a constant size even though our sensation of the object changes.

Question 77

moon illusion

Answer 77

perceive the moon to be larger when closer to the horizon. retinal size the same. perceived distance differs.

Question 78

Emmert's Law

Answer 78

S=RxD

Question 79

Ponzo illusion

Answer 79

over interpret the depth cues in a 2D image

Question 80

Ames illusion

Answer 80

Size of people looks distorted because you are looking at distorted room.

Question 81

Perceptual constancies

Answer 81

Objects appear to be: ▪ The same size when viewed from different distances ▪ The same shape when viewed from different angles ▪ The same colour when viewed in different lighting

Question 82

Shape constancy

Answer 82

Edges within an object change their relative distance to us as we rotate the object or move relative to it. Likewise, the retinal image changes the relative constancy of the perceived shape of an object despite variations in its orientation