Sensation & Perception Chapter 10 Flashcards
cue approach to depth perception
the approach to explaining depth perception that identifies information in the retinal image, and also information provided by aiming and focusing the eyes on an object that is correlated with depth in the scene. some of the depth cues that have been identified are overlap, relative height, relative size, atmospheric perspective, convergence, and accommodation
occlusion
a cue that one object is in front of another
oculomotor cues
depth cue that depends on our ability to sense the position of our eyes and the tension in our eye muscles. accommodation and convergence are oculomotor cues
monocular cues
depth cues that work with only one eye (accommodation, pictorial cues, and movement-based cues)
pictorial cues
sources of depth information that can be depicted in a picture
relative height
objects with their bases closer to the horizon are usually seen as being more distant
relative size
when two objects are of equal size, the one that is farther away will take up less of your field of view than the one that is closer
perspective convergence
when you look down parallel railroad tracks that appear to converge in the distance, for example
familiar size
when we judge distance based on our prior knowledge of the sizes of objects
atmospheric perspective
distant objects appear less sharp
texture gradient
elements that are equally spaced in a scene appear to be more closely packed as distance increases
motion parallax
as we move, nearby objects appear to glide rapidly past us, but more distant objects appear to move more slowly
deletion
a cue that provides information about the relative depth of two surfaces. deletion occurs when a farther object is covered by a nearer object due to sideways movement of an observer relative to the objects
accretion
a cue that provides information about the relative depth of two surfaces. occurs when the farther object is uncovered by the nearer object due to sideways movement of an observer relative to the objects
stereoscopic vision
two-eyed depth perception that takes into account differences in the images formed on the left and right eyes
stereoscopic depth perception
depth perception created by input from both eyes
strabismus
misalignment of the eyes. when this occurs, the visual system suppresses vision in one of the eyes to avoid double vision so the person sees the world with only one eye at a time
binocular disparity
differences in the images on the left and right retinas
corresponding retinal points
points on the retina that overlap if the eyes are superimposed on each other
horopter
an imaginary surface that passes through the point of fixation. images caused by a visual stimulus on this surface fall on corresponding points on the two retinas.
noncorresponding points
images of objects that are not on the horopter
absolute disparity
degree to which these objects deviate from falling on the corresponding points
angle of disparity
amount of the absolute disparity
relative disparity
difference in absolute disparities of objects of a scene
stereopsis
the impression of depth that results from information provided by binocular disparity
stereoscope
a device that presents pictures to the left and the right eyes so that the binocular disparity a person would experience when viewing an actual scene is duplicated. the result is a convincing illusion of depth.
passive method
2 superimposed polarized images with polarized glasses
active method
alternate L and R images 30x/second
lenticular projection
the screen is coated with a film that contains two sets of lenses that direct different images to the left and right eyes
random-dot stereogram
a pair of stereoscopic images made up of random dots. when one section of this pattern is shifted slightly in one direction, the resulting disparity causes the shifted section to appear above or below the rest of the pattern when the patterns are viewed in a stereoscope
correspondence problem
How does the visual system match the parts of the images in the left and right eyes that correspond to one another?
binocular depth cells (disparity-selective cells)
a neuron in the visual cortex that responds best to stimuli that fall on points separated by a specific degree of disparity on the two retinas. also called a disparity-selective cell
disparity tuning curve
a plot of a neuron's response versus the degree of disparity of a visual stimulus. the disparity to which a neuron responds best is an important property of disparity-selective cells, which are also called binocular depth cells.
visual angle
the angle of an object relative to the observer's eye
size constancy
the fact that our perception of an object's size is relatively constant even when we view the object from different distances
Emmert's law
the relationship between the apparent distance of an afterimage and its perceived size. the farther away an afterimage appears, the larger it will seem S = R x D
Müller-Lyer illusion
the right vertical line appears to be longer than the left vertical line, even though they are exactly the same length
misapplied size constancy scaling
a principle, proposed by Richard Gregory, that when mechanisms that help maintain size constancy in the three-dimensional world are applied to two-dimensional pictures, an illusion of size sometimes results
conflicting cues theory
states that our perception of line length in the Müller-Lyer illusion depends on two cues: 1) the actual length of the vertical lines, and 2) the overall length of the figure
Ponzo Illusion
both animals (or lines) are the same size on the page and have the same visual angle, but the one on top appears longer
Ames room
causes two people of equal size to appear very different in size
moon illusion
when the moon is on the horizon, it appears much larger than when it is higher in the sky
apparent distance theory
the moon on the horizon appears more distant because it is viewed across the filled space of the terrain, which contains depth information; but when the moon is higher in the sky, it appears less distant because it is viewed through empty space, which contains little depth information
angular size contrast theory
the moon appears smaller when it is surrounded by larger objects, such as the large expanse of the sky surrounding it
frontal eyes
results in overlapping fields of view, and allows those who have them to use disparity to perceive depth
lateral eyes
do not have overlapping visual fields and cannot use disparity to perceive depth
echolocation
biological sonar system used by bats to avoid objects in the dark
binocularly fixate
two eyes are both looking directly at the object and the two fovea are directed to exactly the same place