Chapter 7: Depth and Size Perception Flashcards
We rely on a system of ________ and ________ for depth perception.
CUES, CLUES
Depth cue
a clue that gives our brain evidence or information about depth
The retina is __d.
2 - essentially flat
We combine information we get from our visual field to _______ depth
INFER
What two types of cues can be inferred from just a single retina (eye)?
pictorial cues
movement-based cues
Occlusion/Interposition
behind an object
Use the idea that when one object is occluded (hidden) “behind” another, the first object is closer
Example of an inference
Use the idea that when one object is occluded (hidden) “behind” another, the first object is closer.
relative height
- Objects closer to the horizon are seen as more distant.
- Below horizon are near
- Above horizon are far
- Closer to bottom are closer
- Closer to top are further
relative size
The more distant an
object is, the smaller
it’s image will be on
the retina
Familiar Size
Knowing the retinal size of familiar objects at a familiar distance allows us to use that retinal size to infer distance
Cue approach to depth perception:
the system whereby depth perception results from three sources of information, monocular cues to depth present in the image, binocular cues from the comparison of images in each eye, and cues from focusing the eyes, such as vergence and accommodation
Monocular depth cues:
depth cues that require only one eye
Pictorial cues:
information about depth that can be inferred from a static picture
Movement-based cues:
cues about depth that can be seen with a single eye in which the inference of distance comes from motion
Occlusion:
a visual cue that occurs when one object partially hides or obstructs the view of a second object; we infer that the hidden object is farther away from us than the object that obstructs it
In linear perspective, parallel lines appear to ___________ as they recede into the distance.
converge
parallel lines serve as a cue to depth
– The larger the distances between parallel lines, the closer the lines must be to the viewer.
In texture gradients, textures become ________ as they recede in the
distance.
finer
- related to relative size
- Key: these are all based on using existing knowledge about our world to make inferences
In atmospheric perspective, objects in the distance appear
_________ and _________ with blue.
blurred; tinged
In atmospheric perspective, closer objects are _______ and well defined; objects further away are _________.
clear; blurred
Relative height:
a visual cue in which objects closer to the horizon are seen as more distant
Relative size:
the fact that the more distant an object is, the smaller the image will be on the retina
Familiar size:
the cue whereby knowing the retinal size of a familiar object at a familiar distance allows us to use that retinal size to infer distance
Linear perspective:
the pictorial depth cue that arises from the fact that parallel lines appear to converge as they recede into the distance
Texture gradient:
a monocular depth cue that occurs because textures become finer as they recede in the distance
Atmospheric perspective:
a pictorial depth cue that arises from the fact that objects in the distance appear blurred and tinged with blue
Shadows:
a depth cue arising because an object is in front of its shadow; the angle of the shadow can provide information about how far the object is in front of the background
Deletion:
the gradual occlusion of a moving object as it passes behind another object
Motion parallax:
a monocular depth cue arising from the relative velocities of objects moving across the retinae of a moving person
Accretion:
the gradual reappearance of a moving object as it emerges from behind another object
Optic flow:
a motion depth cue that involves the relative motion of objects as an observer moves FORWARD or BACKWARD in a scene
Vergence:
the inward bending of the eyes when looking at closer objects
What are the monocular pictorial cues?
Occlusion
relative height
relative size
familiar size
linear perspective
texture gradient
atmospheric perspective
shadowing
What are monocular motion cues?
Motion Parallax
Deletion and Accretion
Optic Flow
When motion parallax is present, objects that move _________ are further away, and objects that move ________ are closer.
slower; faster
_______________ (two words) is related to motion parallax but forward and back.
Optic flow
Referring to optic flow, faraway objects move more _________ (big far-away objects may not appear to move at all!) and closer objects rush by at ____________ (two wrods)
slowly; high speeds
What are the two oculomotor cues?
accomodation
vergence
accomodation
it is an oculomotor cue:
adjusting the lens of the eye
– Ciliary muscles automatic
– We can sense these movements
– Get some cues from them
What is an example of a monocular depth cue:
When our brain uses the information about a shadow to give us a perception of depth.
Give an example of linear perspective using our campus
Looking down the spine, since there are two parallel pathways that seem to be converging from afar
What are the contributions of relative size and familiar size as depth cues? How might they work together to disambiguate perception?
Relative size is a monocular cue that uses the size of an object depending on the how small the image is. The smaller the object lets us know that the object is distant. When it comes to familiar size it adds existing information to the distance we are seeing by the relative size. When we know that an object is usually bigger such as a horse over a flower, even though the flower takes more space on our retina we make sense of the image by stating that the horse is far and the smallest object is close.
Give an example of motion parallax using one of the following contexts: 1) campus 2) the beach 3) 101 highway
Motion Parallax is a monocular depth cue, in which can be seen with only one eye, that uses the relative velocities of objects as a result of the viewer moving or changing position. When this occurs the eye that is being used depends on multiple images and depending on the perceived velocity it provides us information of the depth of the object. For instance the closer the objects are it seems that the they have a higher velocity while the objects that are farther seem to have a lower velocity. Once a fixation point is set, another factor to consider is the direction of the “moving” object. When the objects seem to be “moving” the opposite direction of where the viewer is moving the viewer acknowledges the object to be near, while the objects that are “moving” in the same direction of the viewer are acknowledged as farther objects.
how could you get someone to display “vergence” (or convergence)?
one way to do this could be having someone look at a pencil while holding it as far as possible and then they slowly bring it toward their eyes
What is the difference between crossed and uncrossed disparity? Which corresponds to points closer to the horopter and which corresponds to points farther away from the horopter?
Crossed disparity refers to the points that are closer to us than the horopter, while the uncrossed disparity refers to the points that are farther away from the horopter.
How does binocular disparity arise? What aspects of the placement of the eyes are essential?
Binocular disparity is a binocular depth cue that arises due to the fact that each eye has a slightly different view since they are placed differently on our head. This refers to the image slightly shifting depending on the which eye is being used.
What is a random-dot sterogram? How is it made? What issue does it address?
A random-dot stereogram is a single image that creates the illusion of a 3D object when crossing your eyes. This image is made by a random placement of black and white dots, where the initial image is copied, and then the copied version has the central section either shifted to the right or left. This issue addresses the correspondence problem where we know that it comes before object recognition.
What do random-dot stereograms tell us about how the visual system solves the correspondence problem?
Random-dot stereograms tells us that the correspondence occurs before object recognition, therefore object recognition is not necessary for disparity cues.
stereopsis
the sense of depth we perceive from the visual system’s processing of the comparison of the two different images from each retina
Binocular disparity:
a binocular depth cue because our two eyes are in different locations in our head and
therefore have slightly
Corresponding points:
refers to a situation in which a point on the left retina and a point on the right retina would coincide if the two retinae were superimposed
Noncorresponding points:
refers to a situation in which a point on the left retina and a point on the right retina would not coincide if the two retinae were superimposed
Horopter:
the region in space where the two images from an object fall on corresponding locations on the two retinae
Panum’s area of fusion:
the region of small disparity around the horopter where the two images can be fused into a single perception
Diplopia:
double images, or seeing two copies of the same image; usually results from the images of an object having too much disparity to lead to fusion
Crossed disparity:
the direction of disparity for objects closer to the viewer than the horopter (the image in the left eye is to the right of the image of the object in the right eye)
Uncrossed disparity:
the direction of disparity for objects that are farther from the viewer than the horopter (the image of the object in the left eye is to the left of the position of the image of the object in the right eye)
Zero disparity:
the situation in which retinal images fall along corresponding points, which means that the object is along the horopter
Correspondence problem (depth perception):
the problem of determining which image in one eye matches the correct image in the other eye
Random-dot stereograms:
stereograms in which the images consist of a randomly arranged set of black and white dots, with the left-eye and right-eye images arranged identically except that some of the dots are moved to the left or the right in one of the images, creating either a crossed or an uncrossed disparity
Binocular cells:
cells with two receptive fields, one for each eye; their main function is to match the images coming to each eye
Size–distance invariance:
the relation between perceived size and perceived distance, whereby the perceived size of an object depends on its perceived distance, and the perceived distance of an object may depend on its perceived size
Visual angle:
the angle of an object relative to the observer’s eye
Size constancy:
the perception of an object as having a fixed size, despite the change in the size of the visual angle that accompanies changes in distance
Müller–Lyer illusion:
the illusion where a line that has two lines going away at an angle looks longer than a line of the same length but the end lines angle back across the main line
Ames room:
a specially constructed room where two people of the same size standing in the two back corners will look very different in height
Ponzo illusion:
the illusion in which two horizontal lines are drawn one above the other; both lines are on top of two inwardly angled vertical lines; the top line, where the two vertical lines are closer together, looks longer
Moon illusion:
the illusion where the moon looks larger when it is near the horizon than it does when overhead
Virtual reality:
a computer-generated photograph, image, or environment that can be interacted with in an apparently real way
Corresponding points refers to a situation in which a point on the left retina and a point on the right retina would not coincide if the two retinae were superimposed.
True
False
False
Which statement about visual angles is TRUE?
Larger objects close up can have the same visual angles as smaller objects farther away.
Smaller objects close up can have the same visual angles as larger objects farther away.
As an object moves closer to the viewer, its visual angle on the retina decreases.
As an object moves farther away from the viewer, its visual angle increases.
Smaller objects close up can have the same visual angles as larger objects farther away.
Which term describes a visual clue in which objects closer to the horizon are seen as more distant?
relative height
Melvin sees his friend’s car get smaller and smaller as it gets farther away from his house, but he knows that the car has not really changed size. What concept does this illustrate?
size constancy
A fly lands on your nose and you rotate your eyes to look at it. This is an example of ______.
vergence
Holway and Boring (1941) studied size-distance invariance. They found that without depth cues, participants judged all objects to be ______.
equal in size
Which term describes the type of disparity for objects farther from the viewer than the horopter?
uncrossed disparity
Researchers continue to debate why the MĂĽller-Lyer illusions works as it does.
True
False
True
Monocular depth cues drawn from static images are known as ______ cues.
pictorial
Which of the following best illustrates size constancy?
Bao sees trees on a faraway hill and assumes that they are smaller than they appear.
Darla holds her thumb in front of her face and perceives that it is larger than the bookcase behind it.
Lijun looks at two parallel lines of equal length and perceives that they are converging.
Ed sees a bicycle two blocks away and assumes it is roughly the same size as his own bike.
Ed sees a bicycle two blocks away and assumes it is roughly the same size as his own bike.
