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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