PSYC10003 Sensation & Perception: Visual, Motion, Colour, Depth, and Auditory Topics

Attention

The ability to preferentially process some parts of a stimulus at the expense of other parts.

Overt attention

When you look directly at the thing you are attending to.

Covert attention

When you attend to something without looking directly at it.

Saccades

Rapid eye movements or jumps from one fixation point to another.

Fixations

Brief pauses between saccades where detailed visual information is mainly acquired.

Salience

How much something stands out visually.

Attentional capture

The automatic and involuntary capture of attention by salient stimuli.

Bottom-up attention

Stimulus-driven attention, where attention is automatically captured by features of the stimulus.

Top-down attention

Goal-driven attention, where attention is directed by goals, expectations, or intentions.

Semantic consistency

Whether an object belongs in a scene.

Syntactic consistency

Whether an object is arranged or behaving normally within a scene.

Attention effects

Attention speeds responses, influences appearance, and affects physiological responding.

Binding problem

The problem of how the brain combines separately processed features into one coherent object.

Feature Integration Theory

Proposes that attention solves the binding problem by focusing on one location at a time.

Illusory conjunction

Occurs when features from different objects are incorrectly combined.

Balint's syndrome

Occurs after parietal lobe damage and involves difficulty attending to objects.

Feature search

A visual search where the target differs from distractors by one feature.

Conjunction search

A visual search where the target is defined by a combination of features.

Change blindness

The failure to notice a change in a scene.

Motion transients

Visual signals caused by movement or change that usually attract attention.

Object perception

Difficult due to ambiguous stimuli, partial occlusion, and viewpoint variations.

Structuralism

Claims that sensations are elementary processes that combine to form perceptions.

Gestaltism

Argues that perception is more than the sum of its parts.

Apparent motion

Occurs when two stationary images are perceived as one moving object.

Illusory contours

Contours perceived even though no physical contour exists.

Perceptual organisation

The process by which humans organise visual information to make sense of objects and scenes.

Grouping

The process by which parts of an image are perceptually bound together to form a whole.

Segregation

The process by which parts of a scene are perceptually separated to form distinct objects.

Good continuation

A Gestalt grouping principle where aligned contours are grouped together.

Prägnanz

The principle that perceptual organisation tends to produce the simplest or best possible figure.

Similarity

The principle that similar objects are more likely to be grouped together.

Proximity

The principle that objects close together are more likely to be grouped together.

Common fate

The principle that objects moving in the same direction are grouped together.

Common region

The principle that elements within the same bounded region are grouped together.

Uniform connectedness

The principle that connected regions with the same visual characteristics tend to be grouped together.

Figure-ground segregation

The process of determining what is the figure or object and what is the background.

Figural cues

Cues that make a region more likely to be perceived as the figure.

Convex regions

More likely to be perceived as figures than concave regions.

Experience in figure-ground perception

Once a person recognises a hidden figure, it can be difficult to unsee it.

Gist perception

The rapid extraction of the overall meaning of a scene.

Rudimentary gist

A very basic overall impression of a scene.

Motion perception

Helps break camouflage, attract attention, segregate objects, interpret events, and identify actions.

Structure from motion

Using motion to infer the 3D shape or structure of an object.

Kinetic depth effect

When motion reveals the three-dimensional shape of an object.

Point-light walkers

Created by placing lights on a person's joints and showing only the moving lights.

Akinetopsia

The inability to perceive motion.

Real motion

Occurs when something is actually moving.

Illusory motion

Occurs when motion is perceived even though nothing is physically moving.

Rotating snakes illusion

A static image that creates the perception of motion, likely due to colour and contrast differences.

Korte's Third Law of Apparent Motion

States that when separation between stimuli increases, the alternation rate must decrease for apparent motion to occur.

Motion aftereffect

Occurs when, after staring at motion in one direction, a stationary object appears to move in the opposite direction.

Waterfall illusion

An example of motion aftereffect.

Induced motion

Occurs when a moving background or nearby moving object makes a stationary object appear to move.

Motion-induced blindness

Occurs when visible objects appear to disappear when surrounded by motion.

Motion-induced change blindness

Occurs when motion makes changes harder to notice.

Footsteps illusion

Shows that contrast affects perceived speed.

Aperture problem

Occurs when the ends of a moving line are hidden, making the direction of motion ambiguous.

Terminators

The visible points where a line meets the edges of an aperture.

Barber pole illusion

An example of the aperture problem where lines appear to move vertically.

Colour perception

Helps organisms find objects, determine ripeness, spot danger or poison, and attract mates.

Visible light

Electromagnetic radiation with wavelengths from about 400 to 700 nm.

Opaque object

Does not allow light to pass through; its colour is determined by the wavelengths it reflects.

Transparent object

Allows light to pass through; its colour is determined by the wavelengths it transmits.

Munsell colour system

Describes colours using hue, value, and chroma.

Hue

The colour category, such as red, blue, or green.

Value

The lightness or darkness of a colour.

Chroma

The saturation or intensity of a colour.

Rods

Photoreceptors active in low light, responsible for vision in dim conditions.

Cones

Photoreceptors active in normal or bright light, responsible for colour vision.

Trichromatism

Normal colour vision with three functioning cone types: S, M, and L.

Metamers

Physically different light stimuli that appear the same because they produce the same cone response pattern.

Monochromatism

True colour blindness where there are no functioning cones and vision relies on rods only.

Dichromatism

A colour deficiency where only two cone types function because one cone type is missing.

Opponent-process theory

Proposes that colour vision is processed through opponent channels: red-green, blue-yellow, and black-white.

Colour constancy

The ability to perceive an object as having the same colour despite changes in illumination.

Depth cues

Clues used by the visual system to judge distance.

Oculomotor cues

Depth cues based on the position and state of the eyes.

Convergence

An oculomotor cue where the eyes turn inward when looking at a close object.

Monocular cues

Depth cues available from one eye.

Binocular disparity

Occurs because the left and right eyes are in slightly different positions and receive slightly different retinal images.

Movement-based cues

Depth cues based on movement.

Deletion

Occurs when an object becomes covered or disappears behind another object.

Accretion

Occurs when an object appears or becomes uncovered from behind another object.

Motion parallax

Occurs when nearby objects appear to move faster across the visual field than distant objects as the observer moves.

Disparity

The difference in position of an image in the left and right eyes.

Horopter

The set of points in space that have zero disparity.

Absolute disparity

Disparity relative to the fixation point or horopter.

Correspondence problem

The problem of matching the correct image in the left eye with the correct image in the right eye.

Angular size

Refers to the size of an object's image on the retina.

Size constancy

Perceiving an object as the same real physical size despite changes in retinal image size due to distance.

Size illusions

Occur because the visual system misjudges distance.

Holway and Boring

Investigated how depth cues influence size judgements.

Physical sound

Refers to pressure waves travelling through a medium such as air or water.

Psychological sound

Refers to the perception or experience of hearing.

Sound waves

Travel through air at about 340 m/s and through water at about 1500 m/s.

Pure tone

A sound made of a single sine wave or single frequency.

Frequency

The number of oscillations or cycles per second, measured in hertz (Hz).

Amplitude

The size or height of the pressure wave, usually corresponding to louder perceived sound.

Decibels (dB)

The unit used to measure physical sound intensity or amplitude.

Phons

The unit used to measure perceived loudness.