IllusionA false representation of the environment

Perception

•Selection

•Organization

•Interpretation

Perception

Illusory Contours

Perceived edges that do not physically exist

Visual system fills in the gaps

Inspired Gestalt School:

•Max Wertheimer (1880-1943)•Wolfgang Kohler (1887-1967)•Kurt Koffka (1886-1941)

•Gestalt Grouping Rules

Perception: Selection

Selective attention“Cocktail party effect”The process whereby the brain sorts out, and only attends to, the important messages from the senses.

Feature detectorsSpecialized cells in the brain that respond only to certain sensory information. Based on experience.

HabituationThe tendency of the brain to ignore environmental factors that remain constant.

Perception: Organization

•Form

•Constancy

•Color

•Depth

Organization: Form

Gestalt

ability to perceive the whole stimulus rather than perceiving its discrete part as separate entities

good continuation

Organization: Form

Figure and Ground

see a main object relative to ground

Organization: Form

Proximity

items near each other are grouped together

Organization: Form

Continuity

perceive smooth as continuous patterns

Organization: Form

Closure

fill in the gaps

Organization: Form

Similarity

image chunks that are similar to each other will be grouped together

Violations of Perceptual Organization by Form: Ambiguous Figure

Violations of Perceptual Organization by Form: Ambiguous Figure

Violations of Perceptual Organization by Form: Impossible Figure

Violations of Perceptual Organization by Form: Impossible Figure

Violations of Perceptual Organization by Form: Impossible Figure

Organization by ConstancyPerceptual Constancy:

the tendency for the environment to be perceived as remaining the same even with changes in sensory input

Size

Shape

Color

Brightness

Organization by Color

Trichromatic Theory:color perception results from mixing three distinct color systems - red, green, and blue

Opponent-Process Theory:color perception is based on three systems of color opposites - blue-yellow, red-green, and black-white

Organization by Depth

Depth Perception:the ability to see three dimensions although the images that strike the retina are in two dimensions

Binocular Cues

Monocular Cues

Depth Perception

Binocular Cues: Retinal Disparity

Binocular Cues: Retinal Disparity

Monocular Cue:

Relative Size

assuming same size can discriminate distance

Monocular Cue:

Interposition

blocked objects will appear closer

Monocular Cue:

Relative Clarity

hazy objects are perceived to be further away

Monocular Cue:

Texture Gradient

coarse objects are perceived as being closer

Monocular Cue:

Relative Height

higher objects are perceived to be farther away

Monocular Cue:

Relative Motion

nearer things are perceived to move faster

Monocular Cue:

Linear Perspectives

more line convergence gives the perception of greater distance

Monocular Cue:Relative Brightness

dimmer is perceived to be farther away

Perception: Interpretation

Perceptual Adaptation we adapt to changes in perceptions

Perceptual Setprevious experiences affect our perceptions

Individual Motivationpersonal interests affect our perceptions

Frame of Referenceperceptions change as context changes

Object Recognition• Naïve Template Theory

– Visual object would have to match existing template to be perceived

• Structural Description Theories– Visual object is recognized by its specific parts and the relationships

between its parts.

• Multiple Recognition Committees– Visual objects are recognized by multiple means simultaneously

• Grandmother Cell Theory– Single cells are responsible for recognizing specific objects

Naïve Template Theory

Structural Description Theories

Multiple Recognition Committees

Grandmother Cell Theory