Copyright © Allyn and Bacon 2006Copyright © 2012 Pearson Education, Inc. All Rights Reserved PowerPoint Presentations for Philip G. Zimbardo Robert L.

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


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


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


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?


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


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.


TransductionTransduction

Sensory Pathway• Bundles of neurons that carry information

from the sense organs to the brain


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)


Approximate Sensory Thresholds of Approximate Sensory Thresholds of Five SensesFive Senses


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.


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)


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?


Fundamental Features of the Human Fundamental Features of the Human SensesSenses


The Anatomy of Visual The Anatomy of Visual SensationSensation


Transduction of Light in the RetinaTransduction of Light in the Retina


How Visual Stimulation Goes from the How Visual Stimulation Goes from the Eyes to the BrainEyes to the Brain


How the Visual System Creates How the Visual System Creates Color and BrightnessColor and Brightness

WavelengthWavelength

ColorColor

Intensity Intensity (amplitude)(amplitude)

BrightnessBrightness


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


The Light StimulusThe Light Stimulus



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


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.




Color Blindness• Vision disorder that prevents an individual

from discriminating certain colors


Ishihara Color Blindness TestIshihara Color Blindness Test


Sound WavesSound Waves


How We Hear Sound WavesHow We Hear Sound Waves

Cochlea


Auditory Stimulation Becomes Auditory Stimulation Becomes SensationSensation


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


Decibel Levels Decibel Levels of Different of Different

SoundsSounds


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


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


Receptors for SmellReceptors for Smell


Receptors for TasteReceptors for Taste


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


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


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


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?


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


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


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


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


Shape ConstancyShape Constancy


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


What Is Depicted Here?What Is Depicted Here?


Perceptual IllusionsPerceptual Illusions


Perceptual IllusionsPerceptual Illusions

The Herman Grid

Do you see small gray squares between the black squares?


Six Illusions to Tease Your BrainSix Illusions to Tease Your Brain


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


The Gestalt Laws of Perceptual Grouping

SimilaritySimilarity

ProximityProximity

ContinuityContinuity

Common fateCommon fate

PrägnanzPrägnanz


Gestalt Laws of Perceptual Grouping


Law of PrägnanzLaw of Prägnanz


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


Subjective Contours & ClosureSubjective Contours & Closure


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


Cultural Influences on PerceptionCultural Influences on Perception

Which box is bigger, A or B?


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

Copyright © Allyn and Bacon 2006Copyright © 2012 Pearson Education, Inc. All Rights Reserved PowerPoint Presentations for Philip G. Zimbardo Robert L.

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