psych 230: depth perception

Accommodation

Adjusting lens of eye so that 1 can see near (thick) & far (thin lens)

Vergence

Informing brain about location of objects in space

Occlusion

1 object partially obstructs the view of a 2nd object—tells order of objects

Relative Height

Objects closer to horizon are seen as more distant

Relative Size

The more distant an object, the smaller the image on the retina will be

Familiar Size

We judge distance based on existing knowledge of sizes of objects

Linear Perspective

Parallel lines appear to converge as they recede in distance

Texture Gradients

Textures become finer as they recede in the distance

Atmospheric Perspective

Objects in distance appear blurred and tinged blue

Shadows/Shading

Object in front of its shadow & angle of shadow provides info about how far the object is in front of the background

Motion Parallax

Arises from the motion of a person in the environment
o Faster moving objects are closer to us & slower moving objects are farther away
oNear objects move in opposite direction of you & far away objects move long w/ you and take longer to go by

Deletion

Gradual occlusion of a moving object as it passes behind another object

Accretion

Gradual reappearance of a moving object as it emerges from behind another

Optic Flow

Relative motions of objects—rate of expansion of a ball coming toward you

Stereopsis

Sense of depth that we perceive from the visual system's processing of the comparison of the 2 different images from each retina—use binocular disparity

Binocular Disparity

2 different images b/c 2 diff eyes—each retina has objects located at slightly diff locations

3D Movies

Lens of glasses are diff & capture diff types of light—makes an image for the right eye and a diff image for the left eye—the eyes are not getting both images

Horopter & Corresponding Points

Region in space where 2 images from an object fall on corresponding locations on the 2 retinas

Corresponding Locations

All points on the horopter are corresponding points—depends on the location you are focusing on—points along horopter have 0 disparity

Panum's Area of Fusion

Region of small disparity around horopter where 2 images can be fused into 1 single perception

Diplopia

Results from the images of object having too much disparity to lead to fusion

Correspondence Problem

Which image in 1 eye matches the correct image in the other

Uncrossed Disparity

Direction of disparity for objects that are behind the horopter—the image of the object in the left eye is to the left of the image of the object of the right

Wheatstone Stereograph

Left eye can only see the image on the left and right can only see image on the right—divider in between your eyes
oTake pic on each side w/ slightly diff visual-brain combines images to a 3D image

Anaglyph

Form of a stereogram—used for 3D movies
o Takes 2 pics of a scene and separate them by 6 cm
o 1 pic printed in a shade of 1 color and other pic is printed in a shade of another
o2 pics are integrated into a common image, looks fuzzy under normal viewing, BUT when viewed w/ special color coded anaglyph glasses, each of the 2 images goes into 1 eye allowing for image to emerge

Random Dot-Stereograms

Stereograms where images consist of randomly arranges set of black and white dots, with left eye and right eye images arranges identically except that some of the dots are moved to the left or tight in 1 of the images

oCreates either a crossed OR an uncrossed disparity

Random Dot-Stereograms as Anaglyphs

different sets of dots are supposed to be different colors, you see the different color dots pop out

Visual Reality

Have diff images in left/right eye of rollercoaster & you see yourself going up and down b/c our brain is combining these images to create a 3D image

Forced Perspective Illusion

a picture of women who looks like a giant, but the picture was just taken a certain way that created the illusion

The Anatomy and Physiology of Binocular Perception

- Cells sensitive to binocular disparity in V4 and V1 of occipital lobe
- Binocular cells have 2 receptive fields—1 for each eye
o Function: match images coming to the eye
o Many respond best when the images are on corresponding points on each retina & some respond best to varying degrees of disparity

Critical Period

At 4 months old, babies start to develop stereopsis

Strabismus

one eye is fixating the object and the other eye is turned in too much or turned out too much, the fovea in each eye does not experience the same thing, the brain suppresses the information from the eye that is not fixating on the object

Size-Distance Invariance

Relation between perceived size and perceived distance

oStates that the perceived size of an object depends on its perceived distance, and the perceived distance of an object may depends on its perceived size

Visual Angle

the angle of an object relative to 1's eye

Size Constancy

Perception of an object as having a fixed size, despite change in the size of the visual angle that accompanies the change in distance

The Ponzo Illusion

Looks like the farther away object is bigger, bit it isn't
1. The 2 animals have the same size on the retina
2. Use Depth cues (relative height, linear perspective, texture gradient) & it makes the animal at the top look farther away
3.If objects have the same retinal size, but 1 is farther away, then the farther away object must be bigger in reality

The Müller-Lyer Illusion

When u look at an image with outward facing lines, the inner line looks bigger than the inner line of an image with inward facing lines
· Our brain will interpret the height depending on the context around it
·Inside corners are perceived as being farther away & outside corners as being bigger

The Ames Room Illusion

The room is distorted so the 2 people on different sides of the room look like they are different in size

The Moon Illusion

Moon looks bigger when it is close to the horizon than up in the sky
·We don't judge the sky as a dome-- comes up with idea that horizon is farther away so if the moon is closer to it, it thus looks bigger

Ebbinghaus Illusion

We perceive the inner circle as bigger when it is surrounded by small circles-- the context tricks our brain b/c we compare the inner circle to the outer ones
·Only impacts our "What" pathway, but it does not impact our "Where" pathway

Binocular Rivalry

A phenomenon where a static image leads to alternating perceptions

Binocular Suppression

Information inside 1 retina is being suppressed b/c it doesn't make sense to see it-- why we can't see our nose