Test 2 Psy 2600 Sensation and Perception

Computers + Object Perception

Computers + Object Perception

-Poor object perception -stimulus on receptor is ambiguous -objects can be hidden or blurred

Viewpoint invariance

-Object properties don't change when viewed from different angles -How humans recognize objects from different angles

Perceptual Organization

Small objects become perceptually grouped into larger objects

Gestalt psychology

-Principles of perceptual organization and figure-ground segregation -"Whole is different than the sum of its parts"

Structuralism

-Wundt -Perception results from the summation of sensations

Apparent movement

-Illusion of movement when two objects separated in space are presented rapidly, one after another, separated by a brief time interval -Perceptual organization creates movement (contradicts structuralism)

Illusory contours

Contour that is perceived even though it is not present in the physical stimulus

Principle of good continuation

Points, when connected, result in straight or smoothly curving lines seen as belonging together, following the smoothest path

Principle of Pragnanz/Good Figure/Simplicity

Every stimulus pattern is seen in a way that the resulting structure is as simple as possible

Principle of Similarity

Similar things appear to be grouped together

Principle of Proximity/Nearness

Things that are near each other appear to be grouped together

Principle of Common Fate

Things that are moving in the same direction appear to be grouped together

Principle of Common Religion

Elements that are within the same region of space appear to be grouped together

Principle of Uniform Connectedness

Connected regions of a visual stimulus are perceived as a single unit

Figure-ground segregation

The perceptual separation of an object from its background

Reversible figure-ground

-A figure-ground pattern that perceptually reverses as it is viewed (figure and ground switch) -Ex Rubin's vase-face pattern

Border ownership

When two areas share a border (in figure-ground displays) the border is usually perceived as belonging to the figure

Gibson and Peterson experiment

-Standing woman in a doorframe -Meaningfulness of stimulus matters

Scene

-A view of real-world environments -contains background elements -contains objects organized in meaningful ways relative to each other and the background

Gist of a scene

General description of a scene, can be perceived in 1/4 seconds

Persistence of vision

-Perception of any stimulus persists for about 250ms after the stimulus is physically terminated -Can be disrupted by visual masking

Visual masking stimulus

Visual pattern presented after a visual stimulus to decrease a person's ability to perceive the stimulus. Stops persistence of vision and effective duration of the stimulus

Global image features

Degree of naturalness, openness, roughness, expansion, and colour

Degree of naturalness

-Natural scenes have textured zones and undulating contours -Man-made scenes have horizontal and vertical straight lines

Degree of openness

Open scenes typically have a visible horizon line and contain few objects (Ocean and streets)

Degree of roughness

Smooth scenes (ocean) contain fewer small elements, whereas high roughness contain many small elements and are more complex

Degree of expansion

Convergence of parallel lines (ex. railroad tracks that appear to vanish in distance) have high degree of expansion. Dependent on observers, viewpoint

Physical regularities

-Regularly occurring physical properties of the environment -vertical + horizontal orientations more common than diagonals

schema

Observer's knowledge about what is contained in typical scenes

Likelihood Principle

Helmholtz; we perceive the object that is most likely to have caused the pattern of stimuli we have received

Unconscious Inference

Helmholtz; some perceptions are the result of unconscious assumptions that we make about the environment

Bayesian inference

-Perception determined by accounting for probability -Probability based on past experiences in perceiving properties of objects and scenes

Prior probability

In Bayesian inference, a person's initial estimate of the probability of an outcome

Likelihood

In Bayesian inference, the extent to which the available evidence is consistent with a particular outcome

Binocular Rivalry

-One image presented to OS, one image presented to OD, and perception alternates back and forth between the two images -Attention activates one brain area over another

Brain areas and facial responses

Occipital cortex: initial processing of face information FFA: Face identification Amygdala: Emotional aspects of faces + reactions to facial expressions STS: Evaluate where a person is looking + mouth movements Frontal cortex: Evaluate a face's attractiveness

Visual scanning

Moving the eyes to focus attention on different locations, on objects, or in scenes

Fixation

The brief pause of the eye that occurs between eye movements as a person scans a scene

Saccadic eye movement

Rapid eye movement between fixations that occurs when scanning a scene

Overt vs Covert attention

Overt: involves looking directly at attended object Covert: attention without looking

Visual salience

Characteristics that cause stimuli to stand out and therefore attract attention

Spatial attention

Attention to a specific location

Precueing

A cue stimulus is presented to direct an observer's attention to a specific location where a test stimulus is likely to be presented. Posner used this to show attention enhances processing of a stimulus presented at cued location

Binding

Features (colour, form,motion, location) are combined to create our perception of a coherent object. Occurs across senses

Binding problem

Problem of how neural activity in many separated areas in the brain is combined to create a perception of a coherent object

Feature integration theory (FIT)

Anne Treisman; explains how an object is broken down into feature and how these features are recombined to result in a perception of the object

Preattentive stage (FIT)

Automatic and rapid stage of processing, during which a stimulus is decomposed into individual features

Focused attention stage (FIT)

Stage of processing in which features are combined (requires focused attention)

Balint's Syndrome

Damage to parietal lobe, causing inability to focus attention on individual objects

Inattentional blindness

A stimulus that is not attended is not perceived, even though the person is looking directly at it

Change blindness

Difficulty detecting differences between two visual stimuli presented one after another. Also occurs when part of a stimulus is changed very slowly (Continuity errors)

Load theory of attention

Lavie; the amount of perceptual capacity that remains as a person is carrying out a task determines how well the person can avoid being distracted by task-irrelevant stimuli

Perceptual capacity

The resources a person has for carrying out perceptual tasks

Perceptual load

The amount of a person's perceptual capacity needed to carry out a particular perceptual task

Low-load vs high-load tasks

Low-load: uses small amount of person's perceptual capacity High-load: involve more processing and therefore use more of a person's perceptual capacity

Perceptual completion

Perception of an object as extending behind occluding objects

Habituation vs dishabituation

Habituation: Paying less attention when same stimulus is presented repeatedly Dishabituation: increase in responding that occurs when a stimulus is changed

Task-irrelevant stimuli

A stimulus that does not provide information relevant to the task at hand

Ecological validity

Gibson; An ecologically valid experiment matches its stimuli, conditions, and procedures to those present in the natural world

Optic flow

Flow of stimuli in the environment that occurs when an observer moves relative to the environment (gradient of flow and FOE are important characteristics)

Gradient of flow

Gradient created in optic flow by movement of an observer through the environment

Focus of Expansion (FOE)

The point in the optic flow pattern caused by observer movement in which there is no expansion (Where you are looking towards)

Invariant information

Environmental properties that do not change as the observer moves relative to an object or scene

Self-produced information

Environmental information that is produced by actions of the observer. (Ex: somersaults by experts vs beginner)

Swinging room experiment

Lee and Aronson; posture is corrected by vision

Visual direction strategy

A strategy used by moving observers to reach a destination by keeping their body oriented toward the target

Car Driving Experiment

Land and Lee; drivers don't look at FOE, instead look at the road where they are headed, and look at curves when turning

Wayfinding

Navigating through the environment by perceiving and remembering objects in the environment and their relation to the overall scene, knowing when to turn and in what direction (using landmarks)

Landmarks

Objects on a route that serve as cues to indication where to turn (used in way finding)

Topographical Agnosia

Patients unable to recognize landmarks in real-world environment due to parahippocampal gyrus damage

Cognitive Map

Mental map of the spatial layout of an area of the environment (Tolman; rat experiment in maze with cheese)

Affordances

Information specified by a stimulus pattern that indicates how the stimulus can be used

Parietal Reach Region (PRR)

In parietal cortex, involved in reaching behaviour

Monkey grasp experiment

Fattori; visuomotor grip cells: responds when an object is scene and also when hand grasps same object

Mirror neurons

Neuron in premotor area that respond when monkey grasps an object and when monkey observes someone else grasping the object

Audiovisual mirror neurons

Respond to actions that produce sound

Action-specific perception hypothesis

People perceive their environment in terms of their ability to act on it (perception changes based on skills and difficulty level)

Event

A segment of time at a particular location that is perceived by observers to have a beginning and an end

Event boundary

The point in time when one event ends and another begins

Akinetopsia

Damage to an area of the cortex involved in motion perception causes blindness to motion

Real motion

The physical movement of a stimulus

Illusory motion

Perception of motion when there actually is none

Induced motion

The illusory movement of one object that is caused by the movement of another object that is nearby

Motion aftereffects

Illusion that occurs after a person views a moving stimulus and then sees movement in the opposite direction when viewing a stationary stimulus immediately afterward (ex. waterfall illusion)

Optic array

The structured pattern of light created by the presence of objects, surfaces, and textures in the environment

Local disturbance in the optic array

Occurs when one object moves relative to the environment, so that the stationary background is covered/uncovered by the moving object. Indicates object is moving relative to the environment

Global optic flow

Information for movement that occurs when all elements in a scene move. Indicates the observer is moving and not the scene

Reichardt detector

Neural circuit in which signals caused by movement of a stimulus across the receptors are processed by a delay unit and an output unit so that signals are generated by movement in one direction but not the opposite direction

Output unit

Component of Reichardt detector; compares signals received from 2+ neurons. Activity in this unit is necessary for motion perception

Delay unit

Component of Reichardt detector; explains how neural firing occurs to different directions of movement. Delays transmission of nerve impulses as they travel from receptors towards brain

Corollary discharge theory

Explains motion perception as being determined both by movement of the image on the retina and by signals that indicate movement of the eyes

Image displacement signal (IDS)

In corollary discharge theory, the signal that occurs when an image moves across the visual receptors

Motor signal (MS)

In corollary discharge theory, the signal that is sent to he eye muscles when the observer moves or tries to move their eyes

Corollary discharge signal (CDS)

A copy of the motor signal that is sent to the eye muscles to cause movement of the eye. Copy is sent to the hypothetical comparator of corollary discharge theory

Comparator

Structure hypothesized by the corollary discharge theory. the CDS and IDS meet at the comparator to determine whether movement will be perceived

Real-motion neuron

Neuron in monkey's cortex that responds when movement of an image across the retina is caused by movement of a stimulus, but does not respond when movement across the retina is caused by movement of the eyes

Coherence

In movement perception research when arrays of moving dots are used as stimuli, the degree of correlation between the direction of the moving dots

Transcranial magnetic stimulation (TMS)

Presenting a strong magnetic field to the head that temporarily disrupts the functioning of a specific area of the brain

Aperture problem

A portion of the moving stimulus is seen through a narrow aperture or "field of view" of a neurons' receptive field, causing misleading information about the direction the stimulus is moving

Shorts path constraint

In apparent motion perception, the principle that apparent movement tends to occur along the shortest path between two stimuli (ex: women with hand infront vs behind head)