Sensation & Perception : Depth Perception

Monocular Cues

Depth perception with one eye

Accommodation

Oculomotor Cue

• Lens shape changes

Flattened Accommodation

Far object (3m max)

Curved Accommodation

Close object (20cm maximum)

Pictorial Cues

See depth in painting, photograph, and other 2D images

Overlap

Near object blocks the view of further object

• Occluded portion is visually filled

Farther

______ distance → smaller retinal image size

Closer

_____ to the horizon → looks farther away

Linear Perspectives

Physical parallel lines in the real world appears to converge into “vanishing point”

Farther

______ → more blurring

Shorter, bluer, less

______ wavelength are scattered more, so very distant object looks slightly ____ and _____ distinct.

Atmospheric Perspectives

Mountains in Wyoming look closer than actual distance

Brighter

Relative Brightness : _____ → closer

Brighter

Shadow : Surfacing facing light → _____

True

T/F : In regards to shadows, light comes from above.

Texture Gradients

Linear Perspective + Relative Size = ______ ______

Distant

More _____ parts → smaller elements and more densely packed

texture

Change in _____ → Change in the direction or distance

Motion Parallax

When the observer is in motion, direction and speed of the motion of object depends on the object distance

Closer

_____ → opposite direction

Farther

_____ → slower

Deletion

Object moves backwards in relation to the background

Accretion

Object moves forward in relation to background

Binocular Depth Perception

Depth perception with 2 eyes

• 30% faster

Convergence

Converging angle of 2 eyes will be larger with closer object (closed)

• Physiological cue

Binocular Disparity

Differences of the images from 2 eyes

Corresponding Points

Retinal images on each eye connect to the same part of visual cortex to create a unified perception of depth.

Uncorresponding Points

Retinal images to the different part of the cortex creating a perception of depth that does not match between the two eyes.

Horopter

Imaginary curve that pass the fixation point and corresponding points

Crossed Disparity

Images move out to the sides of the retinas

Uncrossed Disparity

Images move inward on the retinas

Stereopsis

Sense of depth through binocular disparity

Stereoscope

Projection of two slightly different images to 2 eyes produces 3D perception of an object

Autostereoscope

Repeated images in the picture produce 3D

Passive, Active, Lenticular

3 Types of 3D TV

Polarized glasses

Passive

Active

Electronic shutter glasses

Lenticular

Mini senses on screen, no glasses needed

Binocular depth cells, disparity selective cells

Neurons that respond best to binocular disparity are _______ ______ _____ or ______ ______ ______.

Binocular, Binocular disparity

Blake & Hirsch Experiment : Cats were reared, results show that they had few _______ neurons and were unable to use _____ _____ to perceive depth.

Visual Angle

Retinal image angle that is formed based on object size

Smaller, smaller

As distance grows larger, retinal image size grows _____ and the angle gets ______.

Size Constancy

Perception of constant object size regardless of the distance from which it is viewed.

Size contancy

Holway & Boring (1941) : With depth cues → good ____ ____

Emmert’s Law

The perceived size of an object is directly related to the distance from which it is viewed. As the distance increases, the eyes receive a smaller retinal image, yet the brain compensates for this to maintain a perception of size.

Emmert’s Law Equation

S = K (R x D)

• K = Constant

• R = Retinal Image Size

• D = Distance

Muller-Lyer Illusion

A visual illusion where lines of equal length appear to be different lengths due to the addition of arrow-like endings, highlighting the role of perceptual cues in depth perception.

Conflicting Cues Theory

Our perception of the line length depends on…

• Actual length of vertical lines

• Overall length of figure

Ponzo Illusion

A visual illusion that occurs when two horizontal lines are placed over converging lines, leading individuals to perceive the top line as longer than the bottom line, demonstrating depth perception effects.

Explanation for Ponzo Illusion

Misapplied size-constancy scaling

• Based on linear perspective cues, causing the brain to interpret objects at a distance as larger than nearby objects.

Ames Room

A distorted room that creates an optical illusion, making people appear to grow or shrink depending on their position in the room. This effect demonstrates how perception can be influenced by depth cues.

Size-Distance Scaling, Relative Size

Explanations for Ames Room

Ames Room Explanation : Size-Distance Scaling

Woman on the left has smaller visual angle (R)

• Due to the perceived distance (D) being the same, her perceived size (S) is smaller

Ames Room Explanation : Relative Size

Perception of size depends on size relative to other objects

• One woman fills distance between top & bottom of room

• Other woman fills part of distance

  • Thus, woman on right appears taller

Moon Illusion

Moon appears larger on the horizon than when it is higher in the sky

Apparent-Distance Theory

Horizon moon is surrounded by depth cues while moon higher in the sky has none.

Angular Size-Contrast Theory

Moon appears smaller when surrounded by larger objects

Frontal Eyes

____ ____ = Result in overlapping fields of view, are necessary for binocular disparity

Lateral Eyes

____ ____ = Do not result in overlapping fields of view, provide a wider view

Motion Parallax

Locusts use ____ ____ well to judge distance of objects in the dark.