Sensation and Perception Final Exam

binocular disparity

the difference in the retinal images of the two eyes that provides information about depth. Amount of difference depends on distance of object (closer \= more distance)

stereo correspondence problem

the task of identifying features in two images as images of the same feature in the physical world

Autostereograms

Illusions caused when the eye solves the stereo-correspondence problem incorrectly

Horopter

point of fixation in a visual field, as it relates to depth perception

Items on the horopter

zero disparity (distance between objects is the exact same between eyes)

Items in front of horopter

Closer to you, crossed disparity (image is on right side in right eye and left side in left eye)

Items behind horopter

Farther away, uncrossed disparity (item is on the same side in both eyes)

Panum's fusional area

If something is too close or too far, it creates a double image. Binocular depth only exists within a certain distance

binocular rivalry

Left eye and right eye images seen separately. Brain suppresses information from one eye when this happens

3D images

red and blue parts of image are just far enough apart that when you wear 3D glasses, your brain combines the images

Cheshire cat illusion

Put mirror between person and blank wall, so each eye sees one of those objects. This creates binocular rivalry, and brain suppresses image of blank wall. However, when you run your fingers on side with blank wall, that becomes a priority for your vision, and trying to see both images at once, it looks like your hand is going through the person

Tilt after-effect

Receptors for one line orientation are fatigued, making straight lines seem tilted. However, only adapt one eye like this, and show the vertical lines to opposite eye, and it still creates the effect. Evidence of binocular cells

Binocular cells

80% of cells in striate respond to both eyes - compare left and right eye and measure retinal disparity

Critical periods

cells must be developed through exposure

Kitty pirates study

Kittens born blind, and during critical period after developing sight, they had an eyepatch alternating eyes each day. Kitten never got information from both eyes at the same time. Kittens never developed binocular depth perception

strabismus

cross-eyed or wall-eyed. Can be caused by problems with extraocular eye muscles, neurons that control eye muscles, or problems in brain that controls eye movement. Creates double images

ambloypia

One eye has worse acuity than the other, so eyes do not move together properly (lazy eye). Brain starts ignoring worse eye

Signs of vision problems in young children

Tilting head, squinting, or closing one eye

Dimensional Ambiguity

It's difficult to tell distance sometimes based on visual angle

Size constancy

Perceiving an object as the same size, even as visual angle changes. Perceived size \= Retinal size x Depth

Emert's law

perceived size of after-image changes size based on how far away the projection is

Ponzo illusion

Bars that are the same size can appear different sizes if shown on a background with other depth cues. "Farther" object appears larger because it takes up the same visual angle as "closer" object

Moon illusion

A visual illusion involving the misperception that the moon is larger when it is on the horizon than when it is directly overhead. More depth cues to give perspective on how far away the moon is, so the degree visual angle it takes up makes it appear larger

Ames room

Use one eye to look into the room (losing binocular depth perception) and look into a slanted room that appears flat. Person closer to you will appear like a giant

shape constancy

We see the object being the same shape, even though the shape of the retinal projection changes depending on the angle we are looking at it from. Depth information is taken into account when deciding what shape something is

dime box illusion

A small drawing of a square facing away from the viewer will look like it can fit a dime when it cannot. This is because the viewer sees the shape as a 3D square, and not a 2D parallelogram

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.

object perception

The ability to see an object as a whole. Difficult because rods and cones take small pieces of information and brain must put them together to form an object

Object recognition

Taking an image and pairing it with memory representation

Visual-motor coordination

The ability to figure out how to coordinate around an object

Biderman machine

A previously unknown object can be recognized at a later point, even if only shown briefly. Object recognition happens very rapidly and does not depend on knowing what the object is

top-down object recognition

Context surrounding object can help determine how we interpret the object. Depends on previous knowledge, can't be used in new/unexpected scenarios

Perceptual set

We can be pushed into perceiving an object a certain way based on what we are shown before it

Bottom-up object recognition

Taking objects from retina and using them to create new knowledge

spatially parallel

Processing everywhere on image at the same time (pre-attentive/inattentive)

spatially serial

Processing image one area at a time (Attentional spotlight/focus)

3-stage model

1. Low-level vision (pre-attentive analysis, looking at whole image)
2. Visual routines (spatially serial, requires attention, one area at a time)
3. Visual cognition (Matching image with memory representation)

Low-level vision

1. Find discontinuities in objects (helped by lateral inhibition exaggerating outlines)
2. Categorize discontinuities (Eg. by orientation or colour)
3. Group disconnected contours into units (The whole is different from the sum of its parts)

Ganzfeld

a visual field that has no contours

Stabilzed image technique

If object stays on exact same spot on retina, we stop being able to see it. Object edges must change to be perceived.
Eyes are always slightly quivering to make sure image isn't on the same spot on retina for too long

Backwards masking study

If dot is shown very quickly, then followed by a white background, we see the dot. If instead followed by a donut-shape, visual system shows it as a complete circle. Visual system takes time to perceive object edges

Visual search tasks

require that the observer locate a specific target among a set of distractors. \# of other items on display are manipulated. Researchers measure how long it takes subject to decide whether or not target item is on display

Visual search task results

Target present trials take the same time no matter how many other items are on display

Gestalt grouping principles

- Proximity (Group close objects together)
- Similarity (Group similar objects together)
- Continuation (Group objects that can form continuous lines)
- Connectedness (Group connected objects together)
- Closure (More inclined to see closed objects, even when parts are not connected)

Side effects of grouping

Changes in texture can give the illusion of new objects
Formation of illusory contours to create shapes in negative space (Eg. Kanizsa figures)

Discerning figure from ground

- Figures tend to be smaller than backgrounds
- Figures are usually lower in visual field
- Figures have more spatial frequency information
- Figures are usually convex
- Figures usually have meaning and familiarity

Closeup vision

Some scenes are too complex to all take in at once. Have to choose a smaller part to "zoom in" on

Overt orienting

the movement of attention accompanied by movement of the eyes or body

Problems with overt orienting

- Eye muscles are quite slow to move and start
- During eye movements, we cannot gather information
- Eye movements tend to follow the attentional focus (can have something in fovea and still not be paying attention to it)

covert orienting

the movement of attention from one location to another without moving the eyes/body. Much faster form of looking at something

Cuing study

Subjects are given a fixation point to focus their fovea. In the periphery, there is a flash. Then they are asked to press a key when an object appears in the periphery. When the object is on the side with the flash, they are faster, because their attention is already over there, even though they didn't have time to move their eye.

Advantages of attention

- Attended objects are seen more quickly and accurately
- Attended objects appear more detailed and brighter (higher contrast)
- If multiple events happen at the same time, the attended one is seen as happening first

Object file

Vision matches to memory for object recognition. Visual attention combines different attributes together to form a representation of an object

Visual search task for combination

Target object has multiple attributes (eg. white and horizontal). Distractor objects all have one of the target attributes (eg. white or horizontal). Takes longer to find target objects, and it depends on the amount of distractor objects. Target absent trials are even longer.

Spatial relations

Left/right, above/below, etc. Many objects (eg. Letters, faces) can only be discriminated from other objects based on relative spatial information (eg. difference between p and d)

Visual routine

task specific computations that extract task specific information through different fixations. For example, cricket players fixate on the bounce point of the ball just before its impact to compute the desired contact point with the bat.

illusory conjunction

Objects of attention can be misplaced onto other objects.

Gun focus

Victim's focus is on the gun in robberies. Creates trouble with witness testimony, as attributes of people are misplaced onto other people through illusory conjunction

integrative agnosia

A type of visual agnosia, but they have trouble making an object file. Creates problems with spatial relations and combining attributes of an object

Simultagnosia

Can only recognize objects when seeing only one object at a time. Only able to make one object file

Visual cognition

Object file for a scene is matched with long term memory to see if object has been seen before

Visual recognition agnosia

Person can see an object, but they can't identify what they are looking at

Grouping by common fate

things that move together are grouped together

Biological motion

Johansson figures (black bodysuit with lights on joints) can be recognized as human when they move by the light movement alone. We can even recognize sex and mood

Optic flow

the pattern of apparent motion of objects in a visual scene produced by the relative motion between the observer and the scene

global optic flow

Information for movement that occurs when all elements in a scene move. The perception of global optic flow indicates that it is the observer that is moving and not the scene.

Local optic flow

Only a part of the optic array changes (flow of a portion of the retinal image)

Swinging room

People see the illusion of the room swinging forward or backwards, and they lean to compensate

Apparent motion

One static picture then the next creates the illusion of motion (eg. Flip books, animation)

Apparent motion display

Several static pictures with a dot in different corners are shown in very quick succession. Observers feel that they can see the dot moving. If the time is too short, we see them both in the image at the same time. If the time is too long, we see the images as separate

Waterfall illusion

After staring at a waterfall for a long time, other objects seem like they're going up. Image retina system becomes fatigued for downward motion [After-effect]

Image retina system

- Eyes must be still
- Determines motion by the object changing position in retina

Eye head system

- Tracking a movement with eyes and head
- Image stays on same place in retina

Smooth pursuit

The eye moves slowly when tracking an object, so eye head system is used for slower objects

Aubert-Fleischl effect

Person looks at pendulum clock and tracks motion with eyes or keeps their eyes still. Eye head system tends to underestimate speed because it bases measurement on movement of eye muscles, and eye muscles cannot actually keep up with the speed. Image retina tends to be more accurate

Reichardt detector cells

- Cells all lined up in a row
- Cells all have excitatory connections to another neuron
- Every other cell produces inhibitory neurotransmitters to neighbour cell
- Inhibited neighbour cell has an excitatory connection to motion sensitive cell
- When motion moves in a direction for circuit, neighbour cells get APs and are able to send excitatory neurotransmitters to motion sensitive cell before they can be inhibited
- When motion is in opposite direction of circuit, inhibitory cells are able to inhibit their neighbours before they can excite the motion sensitive cell, left with spontaneous activity

Magno retinal ganglia

Start of neural processing of motion

superior colliculus

sends quick motion messages to eye head system

Complex and hypercomplex cells

respond to direction of motion

Kitty in a disco study

Kittens were shown a period of darkness between frames of motion for the beginning of their lives. They ended up not being able to perceive motion properly because of early deprivation

Medial temporal cortex

Important in motion coherence. Complex motion (objects moving together) helps us determine objects (grouping by common fate)

cerebral akinetopsia

Damage to MTC causes the person to lose the ability to perceive motion

medial superior temporal cortex

Brain structure that is important in optic flow

spiral after effect

After looking at a spiral for a long time, it will appear like objects are coming towards you or going away from you, depending on direction of spiral

Superior temporal sulcus

Determines figure perception based on motion (eg, Johansson figures)

Vection

Seeing scenery moving while you're still creates the illusion that you're moving (eg. looking out the window on a train). Conflicting signals between eyes and vestibular system about whether or not you're moving. Vestibular system gets ignored.

Visual capture

Priority on information given to visual information

simulator adaptation syndrome

When in a driving simulator, some people have nausea from the conflict between vestibular and vision systems

corollary discharge theory

- Eye sends sensory image movement signals to comparator when eye moves to let the brain know that things are changing place on the retina
- Eyes are moved by motor signals
- Corollary motor signal is also sent to comparator
- Comparator combines information from sensory image movement and motor signals to determine if there is real movement (If it receives both motor and sensory signals, it cancels out and we don't perceive object movement)

After images with corollary discharge theory

An after-image will seem to move with eye-movements because it stays on same place in retina as the eye moves, so the comparator decides the eye must be tracking a moving object

Curare study

- Curare blocks acetylcholine, which is an excitatory neurotransmitter that causes muscle spasms
- Scientist paralyzed himself with curare to stop his eye muscles from moving
- Scientist formed the intention to make an eye movement
- Object appeared to "jump"
- It's enough to have the intention to form an eye movement from the motor cortex to tell comparator that the eye is moving

Pinnae

- Determines where sounds comes from
- Sound bounces differently in inner-ear folds depending on where sound comes from
- Each person has different folds

Ear canal

- Tube running from outer to middle ear
- Earwax moistens it, but can build up
- A length designed to resonate at frequencies associated with human speech, to make it louder

Ear drum

Thin and delicate layer that moves back and forth in response to sound

Plugged ear canal

Object or earwax in ear canal can create hearing issues

Swimmer's ear

Water stuck in ear canal, can create a bacterial infection

Broken ear drum

Head trauma or very loud sounds can break ear drum. Most common because of Q-tips.

Ossicles

- Small bones that serve as a hammer, anvil, and stirrups
- Makes the sound louder
- Force is concentrated on a small bone in ear
- Uses a lever force to help lift bones

Eustachian tube

- Tube that goes into throat
- Equalizes pressure on inside and outside of ear drum
- Yawning or swallowing opens these tubes up to equalize air pressure
- Buildup of mucus in throat can also cause problems equalizing ear pressure

Greeble recognition study

People who become "experts" in recognizing greebles will light up FFA neurons. This suggests that FFA neurons do not only respond to faces, but any commonly encountered stimulus