Sensation and Perception Unit 3

Ecological Approach to Perception

focuses on specifying info in the environment that is used for perception

Optic Flow

The pattern of motion of stimuli as an observer moves through the environment

Gradient of Flow

Objects closer appear to move faster than objects farther away

Focus of Expansion (FOE)

The point you are moving toward; has little or no motion

Invariant Information

Environmental properties that remain constant despite movement

Affordances

Cues about how an object can be used (e.g., chair = sit, stairs = climb)

Landmarks

Objects that help guide navigation; decision-point landmarks are remembered best

Cognitive Map

A mental representation of the spatial layout of an environment

Place Cells

Neurons in the hippocampus that fire for specific locations

Grid Cells

Neurons that fire in a grid-like pattern to map space

Size-Weight Illusion

Larger objects are perceived as heavier even when weight is equal

Mirror Neurons

Neurons that fire when observing others’ actions

Dorsal Stream Pathway

V1 → V2 → MT (V5) → parietal cortex; processes motion and spatial location

Apparent Motion

Illusion of motion from rapidly changing images (e.g., animation)

Induced Motion

A stationary object appears to move due to nearby motion

Motion Aftereffect

After viewing motion, a still object appears to move

Biological Motion

Motion of living organisms; allows perception of emotion/personality

Representational Momentum

Perception of implied motion in still images

Optic Array

Structured pattern of light from objects in the environment

Local Disruption of Optic Array

When a moving object covers and uncovers the background

MT (Middle Temporal Area)

Brain area responsible for detecting motion direction and speed

MST

Brain area that processes optic flow and guides movement

STS (Superior Temporal Sulcus)

Brain area that processes biological motion

Akinetopsia

Inability to perceive motion due to MT damage

Color Constancy

Perceiving color as stable despite changes in lighting

Lightness Constancy

Perception of lightness remains constant under different illumination

Memory Color

Knowledge of an object’s typical color influences perception

Selective Reflectance

Objects reflect some wavelengths more than others

Hue

The actual color (red, blue, etc.)

Saturation

The intensity or purity of a color

Trichromatic Theory

Color vision is based on three cone types (red, green, blue)

Opponent-Process Theory

Color is processed in opposing pairs (red-green, blue-yellow, black-white)

V4

Brain area important for color perception

Protanopia

Red color deficiency

Deuteranopia

Green color deficiency

Tritanopia

Blue-yellow color deficiency

Convergence

Inward turning of the eyes to focus on close objects

Accommodation

Lens changes shape to focus on objects at different distances

Motion Parallax

Near objects move faster than far objects as you move

Occlusion

Closer objects block farther objects

Relative Size

Smaller retinal image is perceived as farther away (if objects are same size)

Perspective Convergence

Parallel lines appear to converge in the distance

Texture Gradient

Texture appears finer as distance increases

Binocular Disparity

Difference between images in each eye used for depth perception

Visual Angle

The size of an object’s image on the retina

Size Constancy

Objects are perceived as the same size despite distance changes

Perceptual Set

Readiness to perceive something based on expectations

Müller-Lyer Illusion

Lines appear different lengths due to arrow-like fins

Ponzo Illusion

Objects appear different sizes due to converging lines

Ames Room Illusion

Distorted room makes people appear different sizes

Rabbit-Duck Illusion

Ambiguous image seen as either a rabbit or a duck

Rubber Hand Illusion

Fake hand feels like your own due to synchronized touch and vision