chapter 4 sensation & perception
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Chapter 4 Sensation & Perception. Sensation. The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets as sound, a visual image, an odor, a taste, a pain, or other sensory images. The registration of information. Perception. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 4
Sensation & Perception
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Sensation
• The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets as sound, a visual image, an odor, a taste, a pain, or other sensory images.
• The registration of information.
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Perception
• A process that makes sensory patterns meaningful.
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How Do We Interpret Sensations?
• STIMULUS - energy that affects what we do.
• RECEPTORS – specialized cells that convert environmental energies into signals for the nervous system.
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The brain senses the world indirectly because the sense
organs convert stimulation into the language of the nervous system: neural impulses.
How Does StimulationBecome Sensation?
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Transduction
Transformation of one form of energy into another – especially the transformation of stimulus information into nerve impulses.
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Sensory pathways – Bundles of neurons that carry information from the sense organs to the brain.
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Sensory Adaptation• Loss of
responsiveness in receptor cells after stimulation has remained unchanged for a while.
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Thresholds• 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 absolute thresholds for the 5 senses:
• Vision - Candle flame seen at 30 miles on a clear, dark night.
• Hearing - Tick of a watch under quiet conditions at 20 feet.
• Taste - 1 Teaspoon of sugar in 2 gallons of water.
• Smell - 1 Drop of perfume diffused into a three-room apartment.
• Touch - A bee's wing falling on your cheek from 1 centimeter above.
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Thresholds
• Weber’s law – 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 Theory• Signal detection theory –
Perceptual judgment as a combination of sensation and decision-making processes.
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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Subliminal Persuasion
• Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses.
• No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits.
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The Senses: Smell,
Taste, & Touch
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Position and Movement
• Vestibular sense –Sense of body orientation with respect to gravity.– Tells us how our bodies
are positioned.– Movement and motion.
3 semicircular canals
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Position and Movement
• Kinesthetic sense –Sense of body position and movement of body parts relative to each other.– Makes you aware when you are crossing your
legs.– Provides constant sensory
feedback.
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Olfaction
• Sense of smell.
• Smell can influence mood, memory, emotions, mate choice, and the endocrine system (hormones).
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Olfaction
• Olfactory bulbs –Brain sites of olfactory processing.
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Olfaction
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Olfaction
• Pheromones:
Chemical signals released by organisms to communicate with other members of the species.
• Sexual communication
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Taste buds –Receptors for taste (primarily on the upper side of the tongue)
Taste
• Gustation – The sense of taste.
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Taste Receptors
• Sweet• Salty• Sour• Bitter
– Umami• Savory
sensation
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TASTE & SMELL• Our sense of smell is
responsible for about 80% of what we taste.
• All other flavors that we experience come from smell. This is why, when we have a cold, most foods seem bland or tasteless.
• Our sense of smell becomes stronger when we are hungry.
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The Skin Senses
• Touch
• Warmth
• Cold
• Texture
• Pain
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Review from Chapter 3!!!
Sensory information related to the skin senses
is processed within which part of the
brain???
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Answer:
• SOMATOSENSORY CORTEX
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Pain
Gate-control theory• An explanation for
pain control that proposes we have a neural “gate” that can, under circumstances, block incoming pain signals.
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Decreasing Pain
• Endorphins – neurotransmitters that inhibit the release of substance P, and therefore weaken pain sensations.
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Pain
• Placebos –Substances that appear to be drugs but are not.
• Placebo effect –A response to a placebo caused by subjects’ belief that they are taking real drugs.
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Perception brings meaning to sensation, so 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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Perception and Sensation?
• Percept – Meaningful product of a perception.
• What we perceive.
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The Machinery ofPerceptual Processing
• Feature detectors – Cells in the cortex that specialize in extracting certain features of a stimulus.
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The Machinery ofPerceptual Processing
• Binding problem – A major unsolved mystery in cognitive psychology, concerning the physical processes used by the brain to combine many aspects of sensation to a single percept.
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Bottom-Up andTop-Down Processing
• Bottom-up processing – Analysis that emphasizes characteristics of the stimulus, rather than internal concepts (stimulus-driven processing).
• Top-down processing – Emphasizes perceiver's expectations, memories, and other cognitive factors (conceptually-driven processing).
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Perceptual Constancy
• Ability to recognize the same object under different conditions, such as changes in illumination, distance, or location.
Color
Size
Shape
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ILLUSIONS• An incorrect experience of a stimulus
pattern, shared by others in the same perceptual environment.
Muller-Lyer Illusion
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Ponzo Illusion
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Muller-Lyer Illusion
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Ambiguous Figures
• Images that are capable of more than one interpretation.
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Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it dseno't mtaetr in waht oerdr the ltteres in a wrod are, the olny iproamtnt tihng is taht the frsit and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it whotuit a pboerlm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
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The Gestalt Approach• Gestalt psychology –
An approach to psychology that seeks to explain how we perceive overall patterns.
• 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 Approach
• Closure – Tendency to fill in gaps in figures and see incomplete figures as complete.
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The Gestalt Laws of Perceptual Grouping
SimilaritySimilarity
ProximityProximity
ContinuityContinuity
Common fateCommon fate
PrägnanzPrägnanz
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The Gestalt Approach
• Similarity – we tend to group similar objects together in our perceptions.
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The Gestalt Approach
• Proximity – we tend to group objects together when they are near each other.
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The Gestalt Approach
• Continuity – we prefer perceptions of connected and continuous figures to disconnected and disjointed ones.
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The Gestalt Approach
• Common Fate – we tend to group similar objects together that share a common motion or destination.
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The Gestalt Approach
• Law of Prägnanz– The simplest
organization, requiring the least amount of cognitive effort, will emerge as the figure.
ABIRD
IN THETHE HAND
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Depth Perception
• Visual Cliff Experiment
• Develops around 6 months of age
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Depth Perception
• Binocular cues – information taken in by both eyes that aids in depth perception, including convergence and retinal disparity.
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Depth Perception
• Monocular Cues – information about depth that relies on just one eye; includes relative size, light and shadow, interposition, relative motion, and atmospheric perspective.
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Theoretical Explanations for Perception
• Learning-based inference –View that perception is primarily shaped by learning, rather than innate factors.
• Perceptual set –Readiness to detect a particular stimulus in a given context.
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The Hermann Grid
Do you see small gray squares between the black squares?
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The Stroop Effect
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End of Chapter 4