7 Flashcards
What are the 3 types of cues to depth perception?
- oculomotor cues: based on our ability to sense the position of our eyes and tension in our eye muscles
- monocular cues: based on the visual information within one eye
- binocular cues: based on visual information within both eyes
What are 2 oculomotor cues?
- convergence: the inward movement of the eyes when the eyes converge to look at nearby objects
- acoomodation: changing the shape of lens, occurs when we focus on objects at various distances
- we feel these
What are monocular cues/pictorial cues?
depth information that can be depicted in a picture
- occlusion
- relative height
- relative size
- familiar size
- perspective convergence
- atmospheric perspective
- texture gradient
- shadows
What is occlusion cue?
an object that partially covers another is likely in front of it
but cant tell how much further
What is relative height cue?
objects that are higher in the field of vision are likely more distant
Objects on the ground - higher in the field of view appears farther away
Objects in the sky - lower in the field of view appears farther away
What is relative size cue?
relative size: if 2 objects are equal size, the one that takes up more of your visual field is closer
What is familiar size cue?
object distance is influenced our knowledge of object size
Iphone vs ipad (ipad is bigger)
but if they are viewed to be the same size, iphone is closer
What is perspective convergence cue?
parallel lines appear to come togeher in the distance
What is atmospheric perspective cue?
distant objects appear less sharp than nearby objects and have a blue tint
The farther away an object, the more air and particles we have to look through
Distant = less sharp and sometimes have a slight blue tint
Atmosphere scatters short-wavelength light, which appears blue
What is texture gradient cue?
equally spaced elements are more closely packed as distance increases
What is shadows cue?
the blockage of light can help indicate distance
by adding shadow, the spheres location is clearer
What are movement-produced monocular cues
cues during movement that enhance our depth perception
What are the movement produced monocular cues?
- motion parallax
- deletion and accretion
What is motion parallax?
close objects in directino of movement glide rapidly past, but remote objects appear to move slowly
From position 1->2 the tree image move from retina T1 -> T2
For house, the image moves a shorter distance in the retina
Because the image of the tree travels a larger distance across the retina than the house in the same amount time = appears to move more rapidly
What is deletion and accretion cue?
as we move sideways, some things become covered, and other become uncovered
aka occlusion in motion
What is binocular disparity?
the difference in the images on the left and right retinas
left eye lined up relative to the fingers, the right eye is at a different angle sees a different image
What are some binocular cues?
- corresponding retinal points
- absolute disparity
- crossed disparity
- uncrossed disparity
What is corresponding retinal points?
points on the retina that can overlap if the eyes were superimposed on each other
if looking at julie directly, her image will fall on the fovea of both eyes, and so the images are on corresponding retinal points
What is horopter?
a surface where all objects on it will all fall on corresponding points
is there binocular disparity for seeing things on the horopter?
no
What happens if objects are not on the horopter?
their images fall on noncorresponding points
What is absolute disparity?
- the degree to which an image deviates from its corresponding point
- absolute difference between images on the right and left retina
What is angle of disparity?
the amount of absolute disparity
When does binocular disparity occur in terms of the horopter?
on the horopter - no binocular disparity
if fixated object not on it - there is
What is crossed disparity?
when an object is closer to the observer than where the observer is looking
the left eye sees in object (bill) to the right of the fixation point (julie) and the right eye sees bill to the left of the fixation point
both on the inside
look at the image each eyes sees
What is uncrossed disparity?
occurs whenever an object is behind the horopter
in order to fixate on bill, you would need to uncross your eyes
How does crossed and uncrossed disparity help with depth perception?
can determine whether the object is in front of behind a person’s point of fixation
crossed - object in front
uncrossed - object behind
What is stereopsis?
a depth perception provided by binocular disparity
the perception of depth that occurs due to the slight positional differences in the images received by each eye
What is anaglyph 3D?
- the eye after the blue glass can only see the blue image, and red to red
- the brain integrates different images from different eyes and create stereoscopic vision
What are disparity selective cells?
neurons that respond best to a specific degree of disparity
The idea that binocular disparity provides information about the positions of objects in space implies that there should be neurons that signal different amounts of disparity.
What is a disparity tuning curve?
A specific neurons reponsposiveness to different degrees of disparity
This particular neuron responds best when the left and right eye are stimulated to create an absolute disparity of about 1 degree
Which regions have found disparity selective neurons?
V1, M1, V4
What are some brain regions sensitive to and some to others for depth perception?
some sensitive to absolute disparity, some to relative disparity
What is relative disparity?
related to how we judge the distance between two objects
absolute disparity is the actual amount
How can we judge size perception?
visual angle
What is visual angle?
the angle of an object relative to the observer’s eye
it tells us how large the object will be on the back of the eye
What does visual angle depend on?
on the size of an object and its distance from the observer
How can we use visual angle to judge size perception?
When near, the visual angle becomes larger
when far, the visual angle is smaller
a small object that is near and a larger object that is far
What if depth perception information is eliminated, how can we judge size?
the size perception is mainly determined by the retina size of an object (but not by the actual size)
we perceive the sun and moon to be the same size even thought sun is a lot bigger. but as we are unable to percieve their distance, we base our judgement on their visual angles
What is size constancy?
our size perception is relatively constant even when we view the object from different distances
What is size-distance scaling equation?
a mechanism that takes an objects distance into account when judging perceived size
What is Emmert’s law?
if we keep the retinal image size constant, changing the perceived distance can change the perceived size
shows the size-distance scaling effect is working constantly when we look at objects in the environment. visual system takes objects retinal size and its distance to determine our perception of size
What can misapplied size constancy scaling lead to?
illusions
Ponzo and Muller-Lyer illusion
What is ponzo illusion
- both animals are same size = same visualangle
- but one on top appears longer because depth information provided by converging railroad tracks make the top animal appear farther away
- the scaling mechanism corrects for this apparently increased depth and we perceived the top animal to be larger
What is the muller-lyer illusion?
- the retinal sizes of the 2 lines are the same
- left objects seems to be closer to us than the right one
- Both lines are same size, but appear to be at different distance because the fins on the right line make this line look like part of an inside corner of a room
- And the fins on the left line make this line look like part of a corner viewed from outside
- Inside corners appear to “recede” and outside corners jut out”
Our size-distance scaling mechanism treates the inside corner as if its farther away so D is larger and this line therefore appears longer
Perceptual system unconsciously takes depth info into account
And size-distance scaling mechanism adjusts the perceived sizes of the lines accordingly
