Sensation and PerceptionSensation and Perception

Sensation and Perception Sensation

How we detect physical energy from the environment and encode it into neural signals that the brain interprets as sound, odor, taste, pain, and visual images

Perception The process that makes sensory patterns meaningful; draws

heavily on memory, and emotion

Transduction the conversion of physical energy (light, vibration) into a

neural message by neural receptors within a sense organ

SensationSensation Sensory Adaptation Sensory Adaptation

Diminished responsiveness of sensory systems due to Diminished responsiveness of sensory systems due to prolonged stimulation prolonged stimulation

(if it does not change; the sensation shifts to the background of (if it does not change; the sensation shifts to the background of our awareness)our awareness)

Absolute threshold The minimum stimulation necessary to detect light, sound,

pressure, taste, and odor Difference thresholdDifference threshold

The smallest physical difference between 2 stimuli that can be recognized as a difference

Difference threshold = JND (just noticeable difference)

SensationSensation Weber’s Law

Difference threshold from individual to individual JND is proportionate to the intensity of the stimulus (high when

the stimulus is HIGH; low when the stimulus is LOW) “what is SUBliminal to me may be SUPRAliminal to you”

Fechner’s Law The magnitude of a stimulus estimated by a formula

Steven’s Power Law A revision of “Fechner’s Law”

Signal detection theorySignal detection theory– Predicts when we will detect weak signals Predicts when we will detect weak signals

contingent upon the number of “false hits”contingent upon the number of “false hits”Subliminal messagesSubliminal messages– Refers to stimuli presented beneath or near Refers to stimuli presented beneath or near

absolute threshold that is strong enough to absolute threshold that is strong enough to affect a sense organ but WITHOUT conscious affect a sense organ but WITHOUT conscious awarenessawareness

– Ex. Tapes advertised help “stop smoking” or Ex. Tapes advertised help “stop smoking” or “lose weight” during sleep“lose weight” during sleep

– No evidence that subliminal messages are No evidence that subliminal messages are effectiveeffective

VisionVision Retina Retina

Light sensitive layer of cells in the back of the eye; the organ of Light sensitive layer of cells in the back of the eye; the organ of transduction which converts light into a neural messagetransduction which converts light into a neural message

Cornea Cornea Protective layer of the eye that covers the pupil and irisProtective layer of the eye that covers the pupil and iris

LensLens Focuses the rays of light into an image onto the foveaFocuses the rays of light into an image onto the fovea

IrisIris The colored muscle surrounding the pupilThe colored muscle surrounding the pupil

FoveaFovea The section of the retina where images are focuses by the lensThe section of the retina where images are focuses by the lens

Human eyeHuman eye

Vision

• Photoreceptors– Light sensitive cells that convert light to neural

energy • RODS (120 million) photoreceptors that are

sensitive to dim light but NOT color• CONES (6 million) photoreceptors that are

sensitive to color

– Cones that are concentrated in the center of the retina that gives us the sharpest vision is an area called the FOVEA

Table 5.1Myers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Other eye structuresOther eye structures

Bipolar cellsBipolar cells Collect impulses from photoreceptors and sends them Collect impulses from photoreceptors and sends them

to the ganglion cellsto the ganglion cells Bundles of ganglion cells make up the optic nerve Bundles of ganglion cells make up the optic nerve Optic nerve transports visual info from the eye to the Optic nerve transports visual info from the eye to the

brainbrain

Light goes NO further than the retinaLight goes NO further than the retina BlindspotBlindspot

The point on the eye where the optic nerve exits the The point on the eye where the optic nerve exits the eye and there are NO photoreceptorseye and there are NO photoreceptors

Visual cortexVisual cortexTransforms neural impulses into visual Transforms neural impulses into visual

sensations of color, form, boundry and sensations of color, form, boundry and movementmovement

Takes 2 dimensional patterns from each eye Takes 2 dimensional patterns from each eye and assembles them into our 3 dimensional and assembles them into our 3 dimensional worldworld

Combines memories, emotions motives and Combines memories, emotions motives and body position with touch to create a visual body position with touch to create a visual worldworld

ColorColor

Wavelength = colorWavelength = color Amplitude = brightnessAmplitude = brightness BrightnessBrightness

Intensity of light, how much light reaches the retinaIntensity of light, how much light reaches the retina Color or hue does NOT exist outside of the brainColor or hue does NOT exist outside of the brain

Our brain creates color based on the wavelength of Our brain creates color based on the wavelength of light striking our eyeslight striking our eyes

Eye detects visible light (pure energy same as x-rays, Eye detects visible light (pure energy same as x-rays, microwaves, UV rays)microwaves, UV rays)

We have no biological receptors sensitive to other We have no biological receptors sensitive to other portions of the EM (electromagnetic) spectrumportions of the EM (electromagnetic) spectrum

Figure 5.4 The spectrum of electromagnetic energyMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

ColorColor Red---------Red--------- longer waves longer waves Yellow/green---------Yellow/green--------- medium waves medium waves Blue-------Blue------- short waves short waves Opponent-process theoryOpponent-process theory

Bipolar cells process color in either or complementary pairsBipolar cells process color in either or complementary pairs Red/greenRed/green Yellow/blueYellow/blue

the sensation of one inhibits the sensation of its the sensation of one inhibits the sensation of its opponentopponent

Trichromatic theoryTrichromatic theory Different types of cones sense different parts of the light Different types of cones sense different parts of the light

spectrumspectrum

Figure 5.5 Differing eyesMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Dysfunctions of the eyeDysfunctions of the eye

Color blindnessColor blindness Inability to distinguish colorInability to distinguish color Most common type of color blindness is RED/GREENMost common type of color blindness is RED/GREEN More common is color weakness More common is color weakness

Cant distinguish pale colors ie pink and tanCant distinguish pale colors ie pink and tan

Nearsightedness Nearsightedness Images and light are projected in FRONT of the retina Images and light are projected in FRONT of the retina

creating a blurry imagecreating a blurry image

FarsightednessFarsightedness Images and light are projected BEHIND the retinaImages and light are projected BEHIND the retina

Figure 5.8 (a) Normal vision (b) Nearsighted vision (c) Farsighted visionMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Hearing

The transduction of air pressure waves into neural messages is called auditionStrength of the sound wave determines LOUDNESSThe length determines FREQUENCYFrom frequency we can determine PITCH

Long waves have low frequency and low pitchShort waves have high frequency and high pitchDecibels are the measuring unit for sound

Absolute threshold for sound is zero decibels

Outer ear (pinna)Channels sound waves through the auditory canal

Ear drum (tympanic membrane)The membrane that vibrates the waves

Middle earTransmits the vibrations:-- piston

CochleaSnail shaped tube of the inner ear, the vibrations cause

the cochlea’s membrane (oval window) to vibrate; jostling the fluid

This movement causes ripples in the basilar membrane (lined with hair cells)

-Hammer-Anvil-Stirrup

Figure 5.24 Hear here: How we transform sound waves into nerve impulses that our brain

interpretsMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Hearing

Frequency the number of vibrations or cycles the wave completes in a given time (cycles per sec. or Hz)

Amplitude the physical strength of the sound wave; decrease in volume = decreasing amplitude

AuditionSound wave relayed to the inner ear

Science of Hearing

Sound wave is relayed to the Outer ear (pinna)--- ear drum (tympanic membrane) ----Vibrations are sent to 3 bones of the middle ear ---Cochlea (organ of hearing)Focuses vibrations in the basilar membrane ---Basilar membrane converts vibration to neural

message--Stirring of the hairs in the basilar membrane stimulate

nerve endings--Convert mechanical vibrations to neural activity--Neural message travels to the auditory cortex VIA the

auditory nerve

Sound

Sound has 3 qualitiesPitchLoudnessTimbre

Sound frequency determines the highness or lowness of PITCH

Place theoryDifferent frequencies activate different locations on the

basilar membraneFrequency theory

Neurons on the basilar membrane respond at different rates for different sound frequencies

Sound

More intense sound waves produce louder sounds

The quality of sound waves refer to the timbre (sound recognition)

Sound as a physical phenomenon DOES NOT EXIST

Sound is purely a psychological sensation that requires an ear to produce it

Deafness

Conductive deafnessThe ways sound waves are converted to nerve energy

is interruptedUsually due to damage to the structures of the middle

ear Due to trauma or over stimulation

Nerve deafness Impulses from the oval window are sent to the brainDamage to the auditory nerve or higher processing

centersPeople are usually born deaf

Smell

• Your sense of smell is referred to as OLFACTION

• Odors-- receptor proteins associated with specialized hairs in the nose --- olfactory bulbs in the brain

• Olfactory bulbs located in the underside of the brain below the frontal lobes

Smell

• Smell does NOT go through the thalamus• Smell has a connection to memory• Smell is also linked to communication ie

PHERMONES• Phermones are chemical signals released by

organisms of the same species to signal:• Receptivity• Danger• Territorial boundry• Food sources

TasteTaste

Taste + smell = cooperative relationship subtle Taste + smell = cooperative relationship subtle distinctions in taste are usually attributed to distinctions in taste are usually attributed to smellsmell

Sense of taste = gustation Sense of taste = gustation Sweet Sweet BitterBitter Sour Sour SaltySalty umamiumami

TasteTaste Umami ---Umami --- asian cuisine asian cuisine

MSG (monosodium glutamate)MSG (monosodium glutamate) Taste receptors gathered in taste buds Taste receptors gathered in taste buds

Top and side of tongueTop and side of tongue Receptors cluster in papillaeReceptors cluster in papillae

Individuals vary in their sensitivity to tasteIndividuals vary in their sensitivity to taste Taste is linked to the somatosensory cortex of Taste is linked to the somatosensory cortex of

the parietal lobethe parietal lobe Super-sensitivity of your sense of taste Super-sensitivity of your sense of taste

decreases as you agedecreases as you age

TasteTaste

Taste buds are damaged by alcohol, Taste buds are damaged by alcohol, smoke, acids, or hot foodssmoke, acids, or hot foods

Your sense of taste is the MOST resistant Your sense of taste is the MOST resistant to permanent damageto permanent damage

There is a constant renewal of your taste There is a constant renewal of your taste receptorsreceptors

TouchTouchTouch is a mix of 4 different skin sensesTouch is a mix of 4 different skin senses– PressurePressure– WarmthWarmth– ColdCold– painpain

The skin has different specialized nerve The skin has different specialized nerve endings that are sensitive to each BUT endings that are sensitive to each BUT only pressure has identifiable receptorsonly pressure has identifiable receptorsCold + warm = burning HOTCold + warm = burning HOTCold metal = wetnessCold metal = wetness

TouchTouch

Phantom limb sensationsPhantom limb sensations– The brain anticipates receiving The brain anticipates receiving

stimulation from a limb that does not stimulation from a limb that does not existexist

The brain can sense without The brain can sense without functioning sensesfunctioning senses

PainPainPain tells us something is wrong with the bodyPain tells us something is wrong with the bodyPeople born without pain receptors usually die People born without pain receptors usually die earlyearly– Unchecked infectionsUnchecked infections– Joint failureJoint failure

Chronic pain (an alarm that wont stop ringing)Chronic pain (an alarm that wont stop ringing)– HeadachesHeadaches– Backaches Backaches – Arthritis Arthritis – hyperalgesiahyperalgesia

Gate control theory for PAINGate control theory for PAIN– The spine either blocks or allows pain to go to the brainThe spine either blocks or allows pain to go to the brain– Small nerve fibers conduct pain signalsSmall nerve fibers conduct pain signals– Large nerve fibers conduct other signals of stimulationLarge nerve fibers conduct other signals of stimulation

PainPainTissue is injured:Tissue is injured:– in small fibers activate opening the “gate” = in small fibers activate opening the “gate” =

PAINPAIN– Large fibers close the “gate” turning PAIN offLarge fibers close the “gate” turning PAIN off

Many treat chronic pain by stimulating the Many treat chronic pain by stimulating the gate closing activity of the large fibers gate closing activity of the large fibers – MassageMassage– acupuncture acupuncture – electric stimulationelectric stimulation

PAINPAINThe brain can also “psych” itself out by The brain can also “psych” itself out by distracting itself from the pain by focusing distracting itself from the pain by focusing on something else on something else – (ex. Athletes)(ex. Athletes)

Pain ManagementPain Management– Lamaze is a combination of:Lamaze is a combination of:– Relaxation (breathing) + Relaxation (breathing) + – Counter stimulation (massage) + Counter stimulation (massage) + – distraction (visualize a comfortable distraction (visualize a comfortable

environment or counting backwards)environment or counting backwards)

Figure 5.29 Biopsychosocial perspective on painMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Bottom Up processingBottom Up processing Working up from sensory receptors to higher levels of Working up from sensory receptors to higher levels of

processingprocessing Top Down processingTop Down processing

Refers to constructing perceptions on sensations from Refers to constructing perceptions on sensations from “bottom up” processing, experience, and expectations“bottom up” processing, experience, and expectations

Figure 5.1 Sensation and perception: One continuous processMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Sensory compensation and Sensory compensation and Sensory interactionSensory interaction

Sensory compensationSensory compensation– People who lose 1 sense do seem to People who lose 1 sense do seem to

compensate with a slight enhancement compensate with a slight enhancement of other sensory abilitiesof other sensory abilities

– closing eyes during kissing minimizes closing eyes during kissing minimizes distractions and increases sensitivitydistractions and increases sensitivity

Sensory interactionSensory interaction– Where one sense influences anotherWhere one sense influences another– Ex. Taste + smell + texture = FLAVOREx. Taste + smell + texture = FLAVOR

Perception Perception = top down processing Sensation = bottom up processing Selective Attention where our awareness focuses on a limited aspect

of what we experience Ex. Cocktail party effect- focus on 1 voice ignoring many

Inattentional blindness Where your attention is focused on 1 thing; you fail to see visual

objects Change blindness, deafness, choice blindness

Humans focus so strongly on a list or chore they ignore change in stimuli.

Visual capture When our senses send info that competes or conflicts with what

we see VISION DOMINATES

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Perception Gestalt (form or whole)

How we organize our sensations into perceptions Form Perception

Figure/ground Figure is what you focus on Ground is what you ignore Words (figure) Blackboard (ground)

Grouping- helps us construct reality but can lead our perception awry

Proximity- tendency to group figures that are nearby together

Similarity- tendency to group similar objects together

Continuity- tendency to perceive smooth, continuous patterns rather than discontinuous ones

Connectedness- connected = whole and 1 Closure- fill in gaps to create a whole

Figure 6.6 Organizing stimuli into groupsMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Unnumbered 6.6Myers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Figure 6.7 Grouping principlesMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Depth Perception Seeing objects in 3D= depth perception and enables

us to gauge distance Visual cliff and babies perceive depth Binocular cues- Judging the distance of nearby

objects Retinal disparity

The difference between the two images received from the eyes Convergence

The extent in which the eyes converge inward when looking at an object. Greater the strain the closer the object

Figure 6.8 Visual cliffMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Figure 6.9 The floating finger sausageMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Monocular cues- gauging distance (10ft away or 100 ft away) Relative size- perceive the object that casts a smaller retinal image to

be further away Interposition- if one object blocks our view of another we perceive it

as closer Relative clarity- we perceive hazy objects as further away Texture gradient- indistinct texture signals increase distance Relative height- higher objects in our field of vision are perceived to

be further away Linear perspective two parallel lines converge they appear further

away Light and shadow- nearby objects reflect more light than faraway

objects Relative motion-

Light and shadow

interposition

Texture gradient

Figure 6.10 Perspective techniquesMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

Relative motion

Motion perception Phi phenomenon- blinking lights being perceived

as one light moving (ex. A marquee)

ESP ESP- extrasensory perception Telepathy- reading someone’s mind or projecting

ones thoughts Clairvoyance- perceiving remote events Precognition- seeing events before they happen Psychokinesis- telekinesis (moving an object with

your mind) Test a ESP’er to see if it works

Reproducible phenomena and theory to explain

Perceptual Constancy

• Refers to how we recognize an object despite different angles, sizes, distance or illumination

• Because of this we perceive objects as unchanging – Shape constancy– Size constancy– Lightness constancy– Color constancy

Figure 6.13 Shape constancyMyers: Psychology, Eighth EditionCopyright © 2007 by Worth Publishers

• Perceptual set– The mental predisposition to perceive one

thing and not another– Schemas influence our perceptual set– Schemas are formed through our experience