Depth and Size Perception Flashcards
What is absolute distance judgment?
Egocentric localization - you to object
What is relative distance judgment?
Requires object-relative localization - object to object
What are pictorial depth cues?
Can be extracted from a 2D image
Occlusion
Shading and shadows
Atmospheric pressure
Relative size
Familiar size
Linear perspective
Relative height
Texture gradient
What is occlusion?
If object A covers part of object B, then A is seen as closer than B
What are shading and shadows?
Indicates which surfaces are facing the light source and which are not
What is atmospheric pressure?
Greater absolute distance makes objects appear fuzzier, bluer
What is relative size?
Same size object further away produces a smaller visual angle
What is familiar size?
Knowledge of object’s actual size influences the perception of its distance
What is linear perspective?
Apparent convergence of receding parallel lines at a vanishing point
What is the key point in linear perspective?
The vanishing point which determine the horizon
What is relative height?
Below the horizon, higher objects appear father away
Above the horizon, lower objects appear further
What is texture gradient?
Texture elements appear smaller and more densely arranged as they get farther away
What are motion-based depth cues?
Motion parallax
Deletion
Accretion
What is motion parallax?
As an observer moves perpendicular to an object, nearby objects appear to move past more rapidly than faraway objects
What is deletion?
Background object is occluded by foreground object moving in front of it
What is accretion?
Background object is uncovered by foreground object moving out of the way
What are oculomotor depth cues?
Accommodation
Convergence
What does a smaller convergence angle result in?
Farther object
What does a larger convergence angle result in?
Closer object
How do depth cues interact?
Depth cues are rarely used alone
Accuracy in estimating distance is an additive relation between depth cues
Perception of depth is stronger with more cues
What is binocular disparity?
Retinal images of an object fall on disparate points on each eye’s retina
What is stereopsis?
Perception of depth based on retinal disparity alone
What is a horopter?
Imaginary surface passing through a fixation point
What happens if the distal stimulus lies on the horopter?
Then the proximal stimulus will fall on corresponding points on each retina = no disparity
What happens if a distal stimulus is not on the horopter?
Then the proximal stimulus produces disparity
What is the degree of disparity?
The distance between points on each retina
What would result in greater disparity?
Objects being farther from the horopter
What are random-dot stereograms?
Each eye sees the same pattern of random dots - with one exception
Central region in each pattern is shifted over and this creates retinal disparity
The shifted region is perceived as floating above the background
What are single-image random-dot stereograms?
Retinal disparity in autosterograms is produced in opposite was form random-dot stereograms
Usually, two separate images are directed onto the same part of each retina
A single image is observed so that it falls on two different parts of each retina in RIRDS
How to see an autostereogram?
Have a small angle of convergence
Look at autostereogram but don’t change the convergence; should see two overlapping images
Change accommodation to bring images into focus keeping convergence constant
Change convergence until repeating parts of the pattern line up horizontally
What is the correspondence problem?
How is it determined which dots in the left eye match which dots in the right eye, to fuse the two images into one percept?
What are some solutions to the correspondence problem?
A neural-network solution that depends on a number of factors including similarity; matches are made only between elements that are similar
No widely accepted solution
What was Walk and Gibson’s cliff experiment?
Started with a visual cliff
Mammals avoided the cliff, turtles did not
There is an innate component to avoiding cliffs
What was Campos, Bertenthals, and Kermoians experiment?
Younger, precrawling infants tested
Experiment group given walker experience, control group got no experience
Dangled infants over deep side and measured HR
The walker group experienced fear, non-experienced did not
Crawling experience more important than age
Depth perception develops via interaction of appropriate experience and innate factors
What are critical/sensitive periods?
Aspects of depth perception develop at certain chronological ages, given proper environmental experience
What was the task of Holway and borings experiment?
Adjust size of comparison circle to match that of various sized test circles, places at different distances
Visual angle of all test circles is 1°`
What was part 1 of Holway and borings experiment?
Normal viewing
If test circle was large and far, observers chose large comparisons
What was part 2 of Holway and borings experiment?
Depth cues eliminated
Observers looked at test circles through a peephole
All stimuli had the same visual angle, so the size comparison matched the visual angle of the test circle, not the size of the test circle
What happens as the distance from a given object increases?
The retinal image becomes smaller but we do not perceive that
What is size-distance scaling?
Distance taken into account when perceiving size
What must be available for size constancy?
Distance and depth cues or else errors will occur
How do illusions occur?
Caused by misapplied size constancy
Which illusion is weaker in children?
Muller-Lyer illusion
What is the moon illusion?
Horizon moon seems to be larger than overhead moon even though the retinal size and the actual distance are constant
Misjudgment of the moon’s size resulting from a misperception of distance
What is apparent-distance theory?
Objects on the horizon, viewed across the filled space of the terrain, should appear to be further away
Objects overhead, seen through the empty space of sky, should appear closer
What is the eye elevation hypothesis?
Moving eyes upwards makes objects appear smaller
What is Emmert’s law?
Perceived size of an object having a constant visual angle is proportional to the perceived distance of the object
What is the illusion of velocity and size?
The larger the object, the more slowly it appears to be moving
What is the illusion of linear perspective?
Increased perceived distance of the train, contributing to an overestimation of the safe time interval
What is the deceptive geometry of collisions?
As distance to train decreases, the visual angle of the train increases in size
The rate of increase in size is hyperbolic
Overestimation of safe time interval
