Topic 8: Perceiving Depth and Size Flashcards
How are depth and size related?
An inaccurate perception of depth can lead to an incorrect perception of size
Your ability to perceive these distances in the 3D environment is based entirely upon…
The image (2D) that is hitting your retina.
What are the three major groups of depth cues?
Oculomotor cues
Monocular cues
Binocular cues
Cues that rely upon on our ability to sense the position of our eyes and sense the tension in our eye muscles
Oculomotor cues
What are the two types of oculomotor cues?
Convergence
Accomodation
inward eye movements that occur when we look at nearby objects
Convergence
change in the shape of the lens that occurs when we focus on objects at various distance
Accommodation
Cues for depth perception that can work when we use only one eye
Monocular cues
What are the two broad categories that monocular cues can be divided into?
Pictorial cues
Movement-based cues
What are the 7 pictorial monocular cues?
Occlusion
Relative height
Familiar size
Relative size
Perspective convergence
Texture gradients
Shadows
Depth cue in which one object hides or partially hides another object from view, causing the hidden object to be perceived as being farther away
Occlusion
Objects that are higher in the visual field are (usually) further away than objects lower in the visual field
Relative height
Judgment of a distance based on previous knowledge of the size of objects
Familiar size
When two objects are of equal size, the one that is farther away will take up less of the field of view
Relative size
Perception that parallel lines in the distance converge as the distance increases
Perspective convergence
Objects appear more textured when they are closer to us, with less texture being apparent as distance increases
Texture gradients
Help us better determine the location and placement of objects relative to others
Shadows
What are the two movement-based monocular cues?
Motion parallax
Deletion and accretion
As we move, nearby objects appear to move rapidly across our visual field whereas far away objects appear to move more slowly
Motion parallax
Moving sideways, some things become covered, and some things become uncovered
Deletion and accretion
The object that deletes and accretes = perceived as being farther away
Basis of stereoscopic vision is…
Binocular disparity
Occurs when the retinal images of an object fall on different points on the two retinas
Binocular disparity
Points on the retina that would overlap if the eyes were superimposed on top of each other
Corresponding retinal points
Objects that fall on corresponding points in each eye are located on the…
Horopter
Objects that do not fall on the horopter fall on…
non-corresponding retinal points
What occurs when objects fall in front of, or behind, the horopter?
Generates an angle of disparity between the eyes = “binocular disparity”
What is the relationship between location of an object relative to the horopter and the size of the angle?
If the angle is large = object is closer than the horopter
If the angle is small = object is farther than the horopter
The idea that binocular disparity provides information about the position of objects in space suggests that…
There should be neurons somewhere in our brains that fire to different amounts of disparity.
Binocular depth cells/disparity selective cells are present in…
V1
Explain the function of inocular depth cells
Preferentially respond to different amounts of disparity
Some will fire more to objects that are in front of the horopter
Some will fire more to objects that are behind the horopter
Why are binocular cues most useful?
Any distance for any object
Explain the relationship between size and visual angles
When far away, the visual angle is small, so the object is perceived as being small.
When closer, the visual angle increases, so the object is perceived as being big.
Our perception of size remains relatively constant, even when the distance changes, or the visual angle on the retina changes.
Size constancy
Environmental cues that can be used to judge an object’s size
Frames of reference
Judging the size of one object by comparing them to the size of an object we are already, or more, familiar with
relative and familiar size
