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Transcript of Copyright © Allyn and Bacon 2006Copyright © 2012 Pearson Education, Inc. All Rights Reserved...
Copyright © Allyn and Bacon 2006Copyright © 2012 Pearson Education, Inc. All Rights Reserved
PowerPoint PowerPoint Presentations forPresentations for
Philip G. Zimbardo Philip G. Zimbardo Robert L. Johnson Robert L. Johnson Vivian Vivian McCannMcCann
Prepared byPrepared byBeth M. SchwartzBeth M. Schwartz
Randolph CollegeRandolph CollegeThis multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or part, of any images; any rental, lease, or lending of the program.
Seventh Edition
Copyright © Allyn and Bacon 2006Copyright © 2012 Pearson Education, Inc. All Rights Reserved
This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or part, of any images; any rental, lease, or lending of the program.
Chapter 3Chapter 3
Sensation & Perception
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Sensation and PerceptionSensation and Perception
Sensation• A process by which a simulated receptor
create a pattern of neural messages that represent the stimulus in the brain
Perception• A process that makes sensory patterns
meaningful
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The brain senses the world indirectly because the sense organs convert stimulation
into the language of the nervous system: neural
messages.
How Does StimulationBecome Sensation?
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TransductionTransduction
Transduction• Converts a form of physical energy into the
form of neural messages
Sensory Receptors• Specialized neurons that are activated by
stimulation and transduce (convert) the incoming stimulus into electrochemical signals
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Stimulation Becomes PerceptionStimulation Becomes PerceptionFigure 3.1 Stimulation Becomes PerceptionFor visual stimulation to become meaningful perception, it must undergo several transformations. First, physical stimulation (light waves from the butterfly) is transduced by the eye, where information about the wavelength and intensity of the light is coded into neural signals. Second, the neural messages travel to the sensory cortex of the brain, where they become sensations of color, brightness, form, and movement. Finally, the process of perception interprets these sensations by making connections with memories, expectations, emotions, and motives in other parts of the brain. Similar processes operate on the information taken in by the other senses.
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TransductionTransduction
Sensory Pathway• Bundles of neurons that carry information
from the sense organs to the brain
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ThresholdsThresholds
Absolute Threshold• Amount of stimulation necessary for a
stimulus to be detected
Difference Threshold• Smallest amount by which a stimulus can
be changed and the difference be detected (also called just noticeable difference: JND)
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Approximate Sensory Thresholds of Approximate Sensory Thresholds of Five SensesFive Senses
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ThresholdsThresholds
Weber’s Law• The size of the JND is proportional to the
intensity of the stimulus.
• The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low.
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Signal Detection TheorySignal Detection Theory
Sensation depends on the characteristics of the stimulus, the background information, and the detector.
Stimulus eventStimulus event
Neural activityNeural activity
Comparison with Comparison with personal standardpersonal standard
Action (or no action)Action (or no action)
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The senses all operate in much the same way, but each extracts different information
and sends it to its own specialized processing
region in the brain.
How Are the Senses Alike? How Are the Senses Alike? How Are They Different?How Are They Different?
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Fundamental Features of the Human Fundamental Features of the Human SensesSenses
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The Anatomy of Visual The Anatomy of Visual SensationSensation
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Transduction of Light in the RetinaTransduction of Light in the Retina
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How Visual Stimulation Goes from the How Visual Stimulation Goes from the Eyes to the BrainEyes to the Brain
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How the Visual System Creates How the Visual System Creates Color and BrightnessColor and Brightness
WavelengthWavelength
ColorColor
Intensity Intensity (amplitude)(amplitude)
BrightnessBrightness
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How the Visual System Creates ColorHow the Visual System Creates Color
Electromagnetic SpectrumElectromagnetic Spectrum• Entire range of electromagnetic energy; Entire range of electromagnetic energy;
includes radio waves, X-rays, microwaves, includes radio waves, X-rays, microwaves, and visible lightand visible light
Visible SpectrumVisible Spectrum• Tiny part of the electromagnetic spectrum Tiny part of the electromagnetic spectrum
that is visible to our eyesthat is visible to our eyes
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The Light StimulusThe Light Stimulus
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How the Visual System Creates ColorHow the Visual System Creates Color
Trichromatic Theory• Based on three different cone receptors
• Explains initial stages of color sensation
Opponent-Process Theory• Based on bipolar cells
• Colors in complementary pairs
• Explains afterimages
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AfterimagesAfterimages
Afterimages• Sensations that linger after the stimulus is
removed
In the following slide, fix your eyes on the dot in the center of the flag.
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How the Visual System Creates ColorHow the Visual System Creates Color
Color Blindness• Vision disorder that prevents an individual
from discriminating certain colors
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Ishihara Color Blindness TestIshihara Color Blindness Test
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Sound WavesSound Waves
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How We Hear Sound WavesHow We Hear Sound Waves
Cochlea
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Auditory Stimulation Becomes Auditory Stimulation Becomes SensationSensation
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Psychological Qualities of SoundsPsychological Qualities of Sounds
Pitch
• Sensory characteristic of sound produced by the frequency of the sound wave
Loudness
• Sensory characteristic of sound produced by the amplitude (intensity) of the sound wave
Timbre
• Quality of a sound wave that derives from the wave’s complexity
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Decibel Levels Decibel Levels of Different of Different
SoundsSounds
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Position and MovementPosition and Movement
Vestibular Sense• Sense of body orientation with respect to
gravity• receptors in semicircular canals
Kinesthetic Sense• Sense of body position and movement of
body parts relative to each other• receptors in joints, muscles, and tendons
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SmellSmell
Olfaction• Sense of smell
Olfactory Bulbs• Brain sites of olfactory processing
Pheromones• Chemical signals released by organisms to
communicate with other members of the species
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Receptors for SmellReceptors for Smell
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Receptors for TasteReceptors for Taste
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The Skin SensesThe Skin Senses
The skin protects against surface injury, holds in bodily fluid, and helps regulate body temperature.
• Touch
• Warmth
• Cold
• Texture
• Pain
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PainPainArises from intense stimulations• Nociceptors (nerve cells) sense
painful/unpleasant stimuli.• affected by mood and expectation
Phantom Limb• An amputee feels sensations coming from missing
the body part due to the brain generating sensation.
Gate Control Theory• Explains pain control• Involves special interneurons that open or close
the pain pathway running up the spinal cord toward the brain
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Dealing with PainDealing with Pain
Analgesic Drugs•Aspirin: interferes with chemical signal•Morphine: suppresses pain messages
Psychological Techniques•Placebo: mock drug•Placebo effect: change caused by the belief that one is taking a real drug
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Perception brings meaning to sensation; therefore perception produces an
interpretation of the external world, not a perfect representation of it.
What is the RelationshipBetween Perception
and Sensation?
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What is the RelationshipWhat is the RelationshipBetween PerceptionBetween Perception
and Sensation?and Sensation?
Percept • Meaningful product of a perception
Pathways in the Brain • What pathway: temporal lobe
• Where pathway: parietal lobe
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The Machinery of Perceptual ProcessingThe Machinery of Perceptual Processing
Feature Detectors • Cells in the cortex that specialize in
detection of specific stimulus features
Binding Problem • Unsolved mystery concerning the processes
used by the brain to combine many aspects of sensation into a single percept
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Two Complementary ProcessesTwo Complementary Processes
Bottom-Up Processing • Analysis that emphasizes characteristics of
the stimulus
Top-Down Processing • Emphasizes the perceiver’s expectations,
memories, and other cognitive factors
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Perceptual ConstanciesPerceptual Constancies
Perceptual Constancy• Ability to recognize the same object under
different conditions, such as changes in illumination, distance, or location• color constancy• size constancy• shape constancy
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Shape ConstancyShape Constancy
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Perceptual Ambiguity and DistortionPerceptual Ambiguity and Distortion
Illusions• Demonstrably incorrect experience of a
stimulus pattern; shared by others in the same perceptual environment
Ambiguous Figures• Images that allow for more than one
interpretation
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What Is Depicted Here?What Is Depicted Here?
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Perceptual IllusionsPerceptual Illusions
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Perceptual IllusionsPerceptual Illusions
The Herman Grid
Do you see small gray squares between the black squares?
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Six Illusions to Tease Your BrainSix Illusions to Tease Your Brain
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Theoretical Explanations for Perception
Gestalt Psychology• States that much of perception is shaped by
innate factors built into the brain
Figure• Part of a pattern that commands attention
Ground• Part of a pattern that does not command
attention; the background
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The Gestalt Laws of Perceptual Grouping
SimilaritySimilarity
ProximityProximity
ContinuityContinuity
Common fateCommon fate
PrägnanzPrägnanz
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Gestalt Laws of Perceptual Grouping
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Law of PrägnanzLaw of Prägnanz
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The Gestalt ApproachThe Gestalt Approach
Subjective Contours• Boundaries that are perceived but do not
appear in the stimulus pattern
Closure• Tendency to fill in gaps in figures and see
incomplete figures as complete
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Subjective Contours & ClosureSubjective Contours & Closure
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Theoretical Explanations for PerceptionTheoretical Explanations for Perception
Learning-Based Inference• View that perception is primarily shaped by
prior learning and experience
Perceptual Set• Readiness to detect a particular stimulus in a
given context
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Cultural Influences on PerceptionCultural Influences on Perception
Which box is bigger, A or B?
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Depth PerceptionDepth Perception
Nature or Nurture?
Visual Cliff Experiment• Illustrates the developmental age at which
depth is perceived
Binocular Cues• Depend on information taken in by both eyes
Monocular Cues• Depend on information taken in by only one eye