Myers’ EXPLORING PSYCHOLOGY

(6th Ed)

Chapter 5

Sensation & PerceptionModified from:

James A. McCubbin, PhDClemson University

Worth Publishers

Sensation & Perception Sensation

Process by which sensory receptors & nervous system receive & represent stimulus energy

Perception Process of organizing & interpreting

sensory info, enabling us to recognize meaningful objects & events

Bottom-Up Processing Begins with sense receptors &

works up to brain’s integration of sensory info

Top-Down Processing Guided by higher-level mental

processes Construct perceptions drawing on

experience & expectations

Sensation & Perception

Sensation: Basic Principles

Psychophysics Study of relationship between

physical characteristics of stimuli & psychological experience of them

Light - Brightness Sound - Volume Pressure - Weight Taste - Sweetness

Sensation: Thresholds Absolute Threshold

Minimum stimulation needed to detect particular stimulus 50% of time

Difference Threshold (JND) Minimum difference between 2 stimuli

required for detection 50% of time Increases in proportion to size of

stimulus Weber’s law

Sensation: Sensory Adaptation

Sensory adaptationDiminished sensitivity as consequence of constant stimulation

Enable us to focus on informative changes

Vision

(Contains Rods & Cones)

Vision: Receptors in retina

Receptors in the Human Eye

Cones Rods

Number

Location in retina

Sensitivity in dim light

Color sensitive? Yes

Low

Center

6 million

No

High

Periphery

120 million

How the Brain Perceives

Necker Cube

Perceptual Organization

Gestalt Organized whole Tendency to integrate pieces of

information into meaningful wholes

Figure-Ground-Organize visual field into objects (figures) that stand out from surroundings (ground)

Perceptual Organization: Form Perception

Perceptual Organization: Form Perception-Grouping

Grouping Organize stimuli into coherent

groups using certain principles Proximity Similarity Continuity Connectedness Closure

Perceptual Organization: Form Perception-Grouping

Perceptual Organization: Form Perception-Grouping

Gestalt grouping principles are at work here.

Closure

Perceptual Organization: Depth Perception Depth Perception

Ability to see objects in 3D Helps judge distance

Binocular cues (2 eyes) Retinal disparity

Images from 2 eyes differ Closer object, larger disparity

Convergence Neuromuscular cue 2 eyes move inward for near objects

Monocular cues (1 eye)

Perceptual Organization: Depth Perception

Monocular Cues Relative size Interposition Relative height Linear perspective Light & shadow Relative motion

Perceptual Organization: Depth Perception

Perspective Techniques

Perceptual Organization: Depth Perception

Light and Shadow

Perceptual Organization: Depth Perception

Perceptual Constancy Perceptual Constancy

Perceiving objects as unchanging even as illumination & retinal image change

Shape Constancy Size Constancy

Perceptual Constancy: Size-Distance Relationship