©1999 prentice hall gate-control theory of pain experience of pain depends (in part) on whether the...

©1999 Prentice Hall

Gate-Control Theory of Pain• Experience of pain

depends (in part) on whether the pain impulse gets past neurological “gate” in the spinal cord and thus reaches the brain.

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Neuromatrix Theory of Pain• Theory that the matrix

of neurons in the brain is capable of generating pain (and other sensations) in the absence of signals from sensory nerves.

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The Environment Within

• Kinesthesis– The sense of body position and movement of

body parts; also called kinesthesia.• Equilibrium– The sense of balance.

• Semicircular Canals– Sense organs in the inner ear, which contribute to

equilibrium by responding to rotation of the head.

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Perceptual Powers: Origins and Influences

• Inborn abilities and perceptual lessons• Psychological and cultural Influences on

perception

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The Visual Cliff• Glass surface, with checkerboard underneath at different heights– Visual illusion of a cliff– Baby can’t fall

• Mom stands across the gap• Babies show increased

attention over deep side at age 2 months, but aren’t afraid until about the age they can crawl (Gibson & Walk, 1960)

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The Visual Cliff

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Critical Period• If infants miss out on

experiences during a crucial period of time, perception will be impaired.

• When adults who have been blind since birth have vision restored, they may not see well

• Other senses such has hearing may be influenced similarly.

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Psychological and Cultural Influences on Perception• We are more likely to perceive something when we

need it.• What we believe can affect what we perceive.• Emotions, such as fear, can influence perceptions of

sensory information.• Expectations based on our previous experiences

influence how we perceive the world.– Perceptual Set

• A habitual way of perceiving, based on expectations.

• All are influenced by our culture.

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Perceptual Set

• What you see in the center figures depends on the order in which you look at the figures:– If you scan from the left, see an old woman– If you scan from the right, see a woman’s figure

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Puzzles of Perception

• Subliminal Perception• Extrasensory Perception: Reality or Illusion?

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Extrasensory Perception• Extrasensory Perception (ESP):– The ability to perceive something without

ordinary sensory information– This has not been scientifically demonstrated

• Three types of ESP:– Telepathy – Mind-to-mind communication– Clairvoyance – Perception of remote events– Precognition – Ability to see future events

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Context Effects• The same physical

stimulus can be interpreted differently

• We use other cues in the situation to resolve ambiguities

• Is this the letter B or the number 13?

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Parapsychology

• J. B. Rhine conducted many experiments on ESP using stimuli such as these.

• Rhine believed that his evidence supported the existence of ESP, but his findings were flawed.

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Shape Constancy• Even though these images cast shadows of

different shapes, we still see the quarter as round

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Visual Illusions

• Illusions are valuable in understanding perception because they are systematic errors.– Illusions provide hints about perceptual strategies

• In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.

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The Ponzo Illusion• Linear perspective

provides context• Side lines seem to

converge• Top line seems farther

away– But the retinal images

of the red lines are equal!

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Fooling the Eye

• The cats in (a) are the same size• The diagonal lines in (b) are parallel• You can create a “floating fingertip frankfurter” by holding

hands as shown, 5-10” in front of face.

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Hearing

• What we hear.• An ear on the world.• Constructing the auditory world.

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What We Hear• Loudness– The dimension of auditory experience related to

the intensity of a pressure wave.• Pitch– The dimension of auditory experience related to

the frequency of a pressure wave.• Timbre (pronounced “TAM-bur”)– The distinguishing quality of sound; the

dimension of auditory experience related to the complexity of the pressure wave.

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An Ear on the World

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Auditory Localization• Sounds from different

directions are not identical as they arrive at left and right ears– Loudness– Timing– Phase

• The brain calculates a sound’s location by using these differences.

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Other Senses

• Taste: savory sensations.• Smell: The sense of scents.• Senses of the skin.• The mystery of pain.• The environment within.

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Taste: Savory Sensations• Papillae– Knoblike elevations on the tongue, containing the taste

buds (Singular: papilla).• Taste buds – Nests of taste-receptor cells.

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Taste Buds• Photograph of tongue

surface (top), magnified 75 times.

• 10,000 taste buds line the tongue and mouth.– Taste receptors are

down inside the “bud”• Children have more

taste buds than adults.

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Four Tastes

• Four basic tastes– Salty, sour, bitter and sweet.

• Different people have different tastes based on:– Genetics.– Culture.– Learning.– Food attractiveness.

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Smell: The Sense of Scents

• Airborne chemical molecules enter the nose and circulate through the nasal cavity.– Vapors can also enter through the mouth and pass into nasal

cavity.• Receptors on the roof of the nasal cavity detect these

molecules.

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Olfactory System

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Sensitivity to Touch

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An Eye on the World• Retina– Neural tissue lining the back of the eyeball’s

interior, which contains the receptors for vision.

• Rods– Visual receptors that respond to dim light.

• Cones– Visual receptors involved in color vision. Most

humans have 3 types of cones.

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The Structures of the Retina

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Why the Visual System is not a Camera

• Much visual processing is done in the brain.– Some cortical cells respond to lines in specific

orientations (e.g. horizontal).– Other cells in the cortex respond to other

shapes (e.g., bulls-eyes, spirals, faces).• Feature-detectors– Cells in the visual cortex that are sensitive to

specific features of the environment.

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Hubel & Wiesel’s Experiment

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How We See Colors

• Trichromatic theory.• Opponent process theory.

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Trichromatic Theory• Young (1802) & von

Helmholtz (1852) both proposed that the eye detects 3 primary colors– red, blue, & green

• All other colors can be derived by combining these three.

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Opponent-Process Theory• A competing theory of

color vision, which assumes that the visual system treats pairs of colors as opposing or antagonistic.

• Opponent-Process cells are inhibited by a color, and have a burst of activity when it is removed.

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Afterimages

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Test of Color Deficiency

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Constructing the Visual World

• Form perception.• Depth and distance perception.• Visual constancies: When seeing is believing.• Visual illusions: When seeing is misleading.

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Form Perception• Gestalt principles describe the brain’s

organization of sensory building blocks into meaningful units and patterns.

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Figure and Ground• Proximity– Seeing 3 pair of lines in A.

• Similarity– Seeing columns of orange

and red dots in B.• Continuity– Seeing lines that connect

1 to 2 and 3 to 4 in C.• Closure– Seeing a horse in D.

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Depth and Distance Perception• Binocular Cues: – Visual cues to depth or distance that require

the use of both eyes.– Convergence: Turning inward of the eyes,

which occurs when they focus on a nearby object

– Retinal Disparity: The slight difference in lateral separation between two objects as seen by the left eye and the right eye.

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Depth and Distance Perception• Monocular Cues: – Visual cues to depth or distance that can be used

by one eye alone.

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The Ames Room• A specially-built room

that makes people seem to change size as they move around in it

• The room is not a rectangle, as viewers assume it is

• A single peephole prevents using binocular depth cues

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Sensation and Perception

• Defining sensation and perception• The riddle of separate senses.• Measuring the senses.• Sensory adaptation.• Sensory overload.

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Defining Sensation and Perception

• Sensation– The detection of physical energy emitted or

reflected by physical objects.– It occurs when energy in the external

environment or the body stimulates receptors in the sense organs.

• Perception– The process by which the brain organizes and

interprets sensory information.

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Ambiguous Figure

Colored surface can be either the outside front surface or the inside back surface Cannot simultaneously be

both

Brain can interpret the ambiguous cues two different ways

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The Riddle of Separate Sensations• Sense receptors.– Specialized cells that

convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.

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Sensation & Perception Processes

Bottom Up vs. Top Down

• Bottom Up Processing– Taking only the raw data of an item to make a

perceptual decision.

• Top Down Processing– Relying on prior experiences to make a

perceptual decision.

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Selective Attention• Selective Attention:– Focusing awareness on a particular stimulus– Without selective attention we would never

concentrate ever– Cocktail Party Effect

• Selective Attention Accidents

Selective Inattention • YouTube Video! • If your attention has been diverted then you

may NOT see some stimulus – You are studying for psych and you don’t notice

someone sit down beside you

• Change Blindness: Pg.119

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Measuring Senses

• Absolute threshold.• Difference threshold.• Signal-detection theory.

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Absolute Threshold

• The smallest quantity of physical energy that can be reliably detected by an observer.

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Absolute Sensory Thresholds• Vision:

– A single candle flame from 30 miles on a dark, clear night• Hearing:

– The tick of a watch from 20 feet in total quiet• Smell:

– 1 drop of perfume in a 6-room apartment• Touch:

– The wing of a bee on your cheek, dropped from 1 cm• Taste:

– 1 tsp. Sugar in 2 gal. water

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Difference Threshold

• The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared;

• Also called Just Noticeable Difference (JND).

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Signal-Detection Theory• A psychophysical theory that divides the detection of

a sensory signal into a sensory process and a decision process.

Stimulus is

Present

Stimulus is

Absent

Response: “Present”

Hit False Alarm

Response: “Absent”

Miss Correct Rejection

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Sensory Adaptation and Deprivation• Adaptation– The reduction or disappearance of sensory

responsiveness when stimulation is unchanging or repetitious.

– Prevents us from having to continuously respond to unimportant information.

• Deprivation– The absence of normal levels of sensory

stimulation.

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Sensory Overload

• Overstimulation of the senses.• Can use selective attention to reduce sensory

overload.– Selective attention• The focusing of attention on selected aspects of the

environment and the blocking out of others.

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Vision

• What we see.• An eye on the world.• Why the visual system is not a camera.• How we see colors.• Constructing the visual world.

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What We See• Hue

– Visual experience specified by color names and related to the wavelength of light.

• Brightness– Lightness and luminance; the visual experience

related to the amount of light emitted from or reflected by an object.

• Saturation– Vividness or purity of color; the visual experience

related to the complexity of light waves.

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What We See

• Hue• Brightness• Saturation