Unit 13 - Depth and Size Perception

▪ Different Types of Depth Cues

Depth perception comes from monocular cues (visual clues) and binocular cues (eye differences) working together.

▪ Oculomotor Cues

depth perception signals based on feedback from the eye muscles (proprioception) as they adjust to focus on objects, primarily used for nearby objects

o Accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina

o Vergence

occurs when the eyes rotate inward to see a near object and then bend outward (diverge) when we look at a more distant object.

▪ Monocular Pictorial Cues

information about depth that be inferred from a static picture

▪ Monocular Depth Cues

depth cures that require only one eye

o 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 father away from us than the object that obstructs it

When does occlusion (or Interposition) happen?

occurs when one object partially hides the view of a second object

o Relative height

a visual cue in which objects closer to the horizon are seen as more distant

o Relative size

the fact that the more distant an object is, the smaller the image will be on the retina

o 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

o Linear perspective

the pictorial depth cue that arises from the fact that parallel lines appear to converge as they recede into the distance

o Texture gradients

a monocular depth cue that occurs because textures become finer as they recede in the distance

o Atmospheric perspective

a pictorial depth cue that arises from the fact that objects in the distance appear blurred and tinged with blue

o Shadows and shading

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

o Motion parallax

a monocular depth cue arising from the relative velocities of objects moving across the retinae of a moving person

o Deletion

the gradual occlusion of a moving object as it passes behind another object

o Accretion

the gradual reappearance of a moving object as it emerges from behind another object

o Optic flow

the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and the scene

▪ Binocular Cues

the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer and the scene

o Stereopsis

the sense of depth that we perceive from the visual system’s processing of

• The comparison of the two different images from each retina.

o Binocular Disparity

a binocular depth cue because our two eyes are in different locations in our head and therefore have slightly different views of the world

o Three-Dimensional Movies

allow stereoscopic vision to occur

Horopter

the region in space where the two images from an object fall on corresponding locations on the two retinae

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

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

o Stereograms

a picture that uses the principle of binocular disparity to create the perception of a three-dimensional image

o Wheatstone Stereograph

a 3D viewing device that uses mirrors at 90-degree angles to display two slightly different images—one to each eye—creating a vivid, single 3D image through binocular vision

o Anaglyph

another form of stereogram and the technique generally used in recent 3D movies. Use a pair of anaglyph glasses to look at these images (red and blue framed glasses)

o Random-Dot Stereograms

A stereogram in which both images consist of a grid of randomly arranged black and white dots, identical except for the displacement of a portion in one image relative to the other

• an observer who views a random dot stereogram in a stereoscope or as an anaglyph will see a single image with the displaced portion in depth

o Random-dot Stereograms as Anaglyphs

single image with the displaced portion in depth random-dot stereograms as anaglyphs use a pair of anaglyph glasses to examine the image. you should see patterns floating in front of the pattern of black and white dots

o Virtual Reality

the computer-generated photograph, image, or environment that can be interacted with an apparently real way

▪ Forced-Perspective Illusions

our preconceptions/assumptions being defied

▪ Development of Stereopsis

depth perception from binocular disparity Proper alignment of both eyes Normal visual experience during a critical period Develops in early infancy (~3–5 months)

Strabismus

misalignment of the eyes (eyes don’t point to same location) Causes

o Size-distance invariance

the relation between perceived size and perceived distance

• the perceived size of an object depends on its perceived distance, and vice versa

o 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

o The 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

o The Müller-Lyer Illusion

the illusion where a line that has two lines going at an angle looks longer than a line of the same length but the end lines angle back across the main line

o The Ames Room Illusion

a specially constructed room where two people of the same size standing in the two back corners will look very different in height

o The Moon Illusion

the illusion where the moon looks larger when it is near the horizon than it does when overhead

o Ebbinghaus Illusion

causes us to perceive a circle as larger when surrounded by smaller circles and smaller when surrounded by larger circles

▪ Binocular Rivalry

The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes

▪ Binocular Suppression

A form of abnormal vision where one eye dominates the other.

which school of psychology is associated with the following statement: "The perception that emerges from a physical scene may not be directly predicted by the sensory components that is is composed of, but emerges when we integrate the components in a whole”

gestalt psychology

Quiroga et al. (2005) were able to examine single-cell recordings of human beings prior to brain surgery. They found that:

Specific cells in the medial temporal lobe appeared to be specific to individual people

how the visual system knows if an object seen at time 1 is the same object at time 2 is know as the

correspondence problem

. a light of 485nm is presented to a person's visual system. What best describes what happens next?

all three cones systems will respond at varying strengths. Color is perceived from the mis of those responses.

. After we have watched the falling of the water in a waterfall for about a minute, if we look at a blank surface, such as a white wall:

we will get a sense of motion going upward, that is, in the opposite direction of the falling water

If you stare at a bright incandescent light bulb for even a short time and then close your eye, you will contine to see an afterimage of that light bulb for a relatively brief period of time. BUt you will notice that although the light bulb has a yellowish hue, your afterimage will appear somewhat blue. This supports what theory of color vision?

The opponent theory of color vision

Francois is a passenger in a car moving at 65 miles per hour down the highway. When Francois looks out the windows, nearby objects will appear to rush by him in the opposite direction, but objects farther way appear to move along with him. Which depth cue is this associated with?

motion parallax

accommodation is considered an oculomotor cue to depth

true

the problem of determining which image in one eye matches the correct image in the other eye is know as the

correspondence problem