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Sensation & PerceptionSensation & Perception

Fraser’s SpiralFraser’s Spiral

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What Is Sensation?What Is Sensation?

It occurs when a It occurs when a stimulus activates a stimulus activates a sensory receptorsensory receptor

A stimulus is measured A stimulus is measured by the following: size, by the following: size, intensity, duration, intensity, duration, wavelengthwavelength

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What Is Perception?What Is Perception?

The organization of sensory information The organization of sensory information into meaningful experiencesinto meaningful experiences

Psychophysics: the study of how Psychophysics: the study of how physical stimuli are translated into physical stimuli are translated into psychological experiencepsychological experience

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Gustav FechnerGustav Fechner

Created experiments Created experiments that measured sensory that measured sensory data data

Laid the basis for Laid the basis for psychophysicspsychophysics

Black roomBlack roomgardengarden Systematic relationship Systematic relationship

between physical & between physical & mental experiencesmental experiences

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What Is Meant by a What Is Meant by a Threshold?Threshold?

Stimulus—any detectable Stimulus—any detectable input from the env’tinput from the env’t

Threshhold—dividing point Threshhold—dividing point between energy levels that do between energy levels that do & don’t have a detectable & don’t have a detectable effecteffect

Absolute threshold: Absolute threshold: the smallest amount the smallest amount of a stimulus that a of a stimulus that a person can reliably person can reliably detectdetect

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Absolute Thresholds Absolute Thresholds Vision: a flame from a Vision: a flame from a

single candle 30 miles single candle 30 miles awayaway

Hearing: ticking of a Hearing: ticking of a watch 20 feet awaywatch 20 feet away

Taste: one teaspoon of Taste: one teaspoon of sugar in two gallons of sugar in two gallons of waterwater

Smell: one drop of Smell: one drop of perfume in a small perfume in a small househouse

Touch: the wing of a bee Touch: the wing of a bee brushing your cheekbrushing your cheek

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Difference ThresholdDifference Threshold

The minimal difference in the magnitude of The minimal difference in the magnitude of energy needed for people to distinguish energy needed for people to distinguish between two stimulibetween two stimuli

AKA Just Noticeable DifferenceAKA Just Noticeable Difference Weber’s law and expertsWeber’s law and experts

The size of a JND is proportionate to the size of the The size of a JND is proportionate to the size of the initial stimulusinitial stimulus

Full backpack—won’t notice adding a spiralFull backpack—won’t notice adding a spiral Empty backpack—will notice itEmpty backpack—will notice it Sample Video

Fechner’s LawFechner’s Law

The magnitude of a sensory experience The magnitude of a sensory experience is proportional to the magnitude of JNDs is proportional to the magnitude of JNDs that the stimulus causing the experience that the stimulus causing the experience is above absolute thresholdis above absolute threshold

1 lamp1 lamp2 lamps2 lamps3 lamps3 lamps

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Signal-Detection TheorySignal-Detection Theory

The study of The study of people’s people’s tendencies to tendencies to make correct make correct judgments in judgments in detecting the detecting the presence of presence of stimulistimuli

Signal Present

Signal Absent

Says YES “present”

HIT FALSE ALARM

Says NO“absent”

MISS Correct Rejection

Other examples of signal Other examples of signal detection theory:detection theory:

Listening for pizza guyListening for pizza guy Searching for cancer cellsSearching for cancer cells Home alone soundsHome alone sounds Military patrolsMilitary patrols

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The Stroop EffectThe Stroop Effect

A B

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Processing StimuliProcessing Stimuli Preattentive process—extracting information automatically Preattentive process—extracting information automatically

& simultaneously when presented with stimuli (makes it & simultaneously when presented with stimuli (makes it hard to read the words with competing colors)hard to read the words with competing colors)

Attentive process—considers only one part of the stimuli at Attentive process—considers only one part of the stimuli at a timea time

Selective attentionSelective attention Awareness Test 1 1 Awareness Test 2

Cocktail Party Phenomenon--being able to focus one's Cocktail Party Phenomenon--being able to focus one's auditory attention on a particular stimulus while filtering out auditory attention on a particular stimulus while filtering out a range of other stimuli, much the same way that a a range of other stimuli, much the same way that a partygoer can focus on a single conversation in a noisy partygoer can focus on a single conversation in a noisy roomroom

Subliminal PerceptionSubliminal Perception Registration of sensory input without Registration of sensory input without

conscious awarenessconscious awareness ““Eat popcorn” (1957)Eat popcorn” (1957) Defenseless!?!Defenseless!?! Evidence that perception without awareness Evidence that perception without awareness

can take placecan take place Effects are VERY minimalEffects are VERY minimal Stairway to Heaven—Led Zeppelin Another One Bites the Dust—Queen http://jeffmilner.com/backmasking/index.html

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Sensory AdaptationSensory Adaptation

Senses are most Senses are most responsive to responsive to increases and increases and decreases rather than decreases rather than ongoing unchanging ongoing unchanging stimulationstimulation

Our senses have the Our senses have the ability to adaptability to adapt

HabituationHabituation (Stinky trash; itchy (Stinky trash; itchy

sweater)sweater)

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Vision Vision Cornea: “window” at Cornea: “window” at

the front of the eye; the front of the eye; light enters here and light enters here and the image is flippedthe image is flipped

Pupil: the opening in Pupil: the opening in the iris that regulates the iris that regulates the amount of lightthe amount of light

Lens: the flexible and Lens: the flexible and transparent part of the transparent part of the eye that changes its eye that changes its shape to focus light in shape to focus light in the retinathe retina

Retina: the innermost Retina: the innermost coating of the back of coating of the back of the eyethe eye

Video clip: how vision works

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Pupil

Iris

Lens

Optic Nerve

retina

Cornea

vitreous

2020

The Human Eye: Rods The Human Eye: Rods and Conesand Cones

Cones require more Cones require more light than rods and light than rods and work best in daylightwork best in daylight Color visionColor vision

Rods are more Rods are more important for night important for night visionvision Black and white visionBlack and white vision

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The Fovea and the Blind The Fovea and the Blind SpotSpot

Fovea: the part of the Fovea: the part of the retina that retina that corresponds to the corresponds to the center of our gazecenter of our gaze

Blind spot: the part of Blind spot: the part of the retina where the the retina where the optic nerve leaves optic nerve leaves the eye (Optic Disc)the eye (Optic Disc)

Nearsighted vs. Nearsighted vs. farsightedfarsighted

Peripheral Vision clip

Visual PathwayVisual Pathway

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On the RETINA:

Rods & Cones Bipolar Cells Ganglion Cells (Transduction) Out the eye through the Optic Nerve Optic Chiasm Thalamus Visual Cortex in Occipital Lobe

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Visual Pathways to the Visual Pathways to the BrainBrain

Input from the right half Input from the right half of the visual field strikes of the visual field strikes the left side of each the left side of each retina and is transmitted retina and is transmitted to the left hemisphere to the left hemisphere (shown in red)(shown in red)

Input from the left half of Input from the left half of the visual field strikes the visual field strikes the right side of each the right side of each retina & is transmitted to retina & is transmitted to the right hemisphere the right hemisphere (shown in green)(shown in green)

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David HubelDavid Hubel

Won the Nobel Prize for his work on Won the Nobel Prize for his work on how humans transform sensory how humans transform sensory informationinformation

Planted electrodes in a cat’s visual Planted electrodes in a cat’s visual cortexcortex

Feature detectionFeature detection Their experiment involved implanting Their experiment involved implanting

electrodes into a cat's visual cortex. They electrodes into a cat's visual cortex. They then flashed the different visual stimuli on a then flashed the different visual stimuli on a screen within the cat’s field of vision and screen within the cat’s field of vision and observed which cells fired in response to the observed which cells fired in response to the different stimuli. They called these cells different stimuli. They called these cells “feature detectors.”“feature detectors.”

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LightLight

The visible portion of the electromagnetic The visible portion of the electromagnetic spectrumspectrum

The colors we see are different The colors we see are different wavelengths of lightwavelengths of light

We see color when light waves hit We see color when light waves hit objects and bounce back to us at varying objects and bounce back to us at varying speedsspeeds

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WavelengthWavelength determines color determines color Longer = red / shorter = violetLonger = red / shorter = violet

AmplitudeAmplitude determines brightness determines brightness PurityPurity determines saturation determines saturation

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Color DeficiencyColor Deficiency

Occurs when a person’s cones do not Occurs when a person’s cones do not function properlyfunction properly

Different types of color deficiency:Different types of color deficiency:

A. Some see certain colorsA. Some see certain colors

B. Totally color deficientB. Totally color deficient

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Color VisionColor Vision

Color receptors in the Color receptors in the retina transmit retina transmit messages to the brain messages to the brain when visible lights when visible lights having different having different wavelengths stimulate wavelengths stimulate themthem

Hermann von HelmholtzHermann von Helmholtz

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Thomas Young’s WorkThomas Young’s Work The three primary colors of light The three primary colors of light

(red, green, blue) combine to (red, green, blue) combine to form whiteform white

Young showed that you could Young showed that you could create any color of light by create any color of light by mixing these component colors mixing these component colors and varying their brightnessand varying their brightness

Trichromatic theory—Trichromatic theory—Said the Said the eye has 3 color receptors eye has 3 color receptors (cones). 3 cones have differing (cones). 3 cones have differing sensitivities to different sensitivities to different wavelengths of light—allowing wavelengths of light—allowing us to see different colors.us to see different colors.

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Opponent Process Opponent Process Theory: AfterimagesTheory: Afterimages

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Complementary Complementary AfterimageAfterimage

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AfterimageAfterimage

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Counter-Rotating SpiralsCounter-Rotating Spirals

Fatiguing your eyes:Fatiguing your eyes:

Counter-Rotating Spirals IllusionCounter-Rotating Spirals Illusion

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HearingHearing

Depends on sound Depends on sound waves or vibrationswaves or vibrations

Sound waves pass Sound waves pass through various bones in through various bones in the inner earthe inner ear

Thin, hair-like cells move Thin, hair-like cells move back and forthback and forth

Sound LocalizationSound Localization

Cupping earsCupping ears Sound localizationSound localization

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LoudnessLoudness

Decibels: measures of Decibels: measures of loudnessloudness

Each 10-decibel Each 10-decibel increase makes a sound increase makes a sound 10 times louder10 times louder

Sound travels through Sound travels through the air at 1130 feet per the air at 1130 feet per secondsecond

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PitchPitch

The highness or lowness The highness or lowness of a sound that of a sound that corresponds to the corresponds to the frequency of a sound frequency of a sound wavewave

The ear senses sound The ear senses sound waves that vary from 20 waves that vary from 20 to 20,000 cycles per to 20,000 cycles per secondsecond

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The Path of SoundThe Path of Sound

Sound waves are Sound waves are funneled by the outer ear funneled by the outer ear to the eardrum, causing it to the eardrum, causing it to vibrateto vibrate

Ossicles and oval Ossicles and oval window, cochleawindow, cochlea

IN THE COCHLEA:IN THE COCHLEA: Basilar membranes Basilar membranes

(Transduction), Organ of (Transduction), Organ of Corti, hair-cell receptorsCorti, hair-cell receptors

Hearing pathway animationHearing pathway animation

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Sound waves vibrate bones of the middle ear

Stirrup hits against the oval window of cochleaSets the fluid inside in motion

Hair cells are stimulated with the movement of the basilar membrane

Physical stimulation converted into neural impulses

Sent through the thalamus to the auditory cortex (temporal lobes)

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Hearing LossHearing Loss

30 million Americans 30 million Americans have hearing problemshave hearing problems

2 million are deaf2 million are deaf Causes: birth defects, Causes: birth defects,

disease, advanced age, disease, advanced age, injury, overexposureinjury, overexposure

Conduction DeafnessConduction Deafness Caused by the failure of Caused by the failure of

the three tiny bones the three tiny bones inside the middle ear to inside the middle ear to pass along sound waves pass along sound waves to the inner ear or the to the inner ear or the failure of the eardrum to failure of the eardrum to vibrate in response to vibrate in response to sound waves sound waves

Possible cause is a build-Possible cause is a build-up of fluidup of fluid

Hearing aids Hearing aids Normal hearing may Normal hearing may

return.return.

Sensory-Neural DeafnessSensory-Neural Deafness

Damage to the inner Damage to the inner ear. Most often caused ear. Most often caused by loss of hair cells by loss of hair cells that will not that will not regenerate”regenerate”

Damage to the Damage to the auditory nerve.auditory nerve.

Cochlear implants can Cochlear implants can help patients with this help patients with this form of deafness.form of deafness.

Video: First time hearing with Video: First time hearing with cochlear implantcochlear implant Video: Boy gets auditory nerve

implant

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Stimulation DeafnessStimulation Deafness

Exposure to very loud Exposure to very loud soundssounds

Prolonged exposure Prolonged exposure to 85 dB can cause to 85 dB can cause stimulation loss.stimulation loss.

Ringing sound can Ringing sound can mean hair cells have mean hair cells have been damagedbeen damaged

Video: How Old are Your Video: How Old are Your EarsEars

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Smell and TasteSmell and Taste

The chemical sensesThe chemical senses ““gustatory system”—gustatory system”—

sense system for tastesense system for taste ““olfactory system”—olfactory system”—

system for smellsystem for smell Nerve impulses travel Nerve impulses travel

through the olfactory through the olfactory nerve to the olfactory nerve to the olfactory bulb in the brain, causing bulb in the brain, causing sensation of specific sensation of specific odorsodors

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Supertasters vs. nontastersSupertasters vs. nontasters People who have greater People who have greater

taste sensibilities than otherstaste sensibilities than others Supertasters have two to Supertasters have two to

three times more taste buds three times more taste buds than normalthan normal

Gender & ethnic differences Gender & ethnic differences in taste sensitivityin taste sensitivity Asian women most likely to be Asian women most likely to be

“super” “super” White males least likely; White males least likely;

evolutionary perspective—evolutionary perspective—women as gatherers--women as gatherers--supertasterssupertasters

Video: SupertastersVideo: Supertasters

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The Olfactory BulbThe Olfactory Bulb

Located in the front of Located in the front of the brain above the the brain above the nostrilsnostrils

Olfactory cortex is Olfactory cortex is located in the temporal located in the temporal lobelobe

Connections to the Connections to the limbic systemlimbic system

Sensations are created by chemical reactions on your taste buds (gustation)

Taste is heavily influenced by smell – this is called sensory interaction

Taste buds==neural impulse==thalamus==cortex

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TASTE QUALITIESTASTE QUALITIES

(taste is a bunch of B (taste is a bunch of B S’s!)S’s!)

•BBitteritter

•SSourour

•SSaltyalty

•SSweetweet

FLAVOR DEPENDS ON…•Temperature

•Odor

•Texture

•Taste(I T.O.T.T. you about flavor)

http://www.npr.org/templates/story/story.php?storyId=1813416Study: Tastes Form in Infancy

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SkinSkin The skin is the largest The skin is the largest

sensory organsensory organ Touch, pressure, warmth, Touch, pressure, warmth,

cold, pain, fine touchcold, pain, fine touch Example: “wetness” is from Example: “wetness” is from

touch and coldtouch and cold 1.5 million receptors for 1.5 million receptors for

touch and pressure, touch and pressure, somatosensory cortexsomatosensory cortex

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Pathways for Pain Pathways for Pain SignalsSignals

Receptors send pain Receptors send pain signals to the brain along signals to the brain along two pathwaystwo pathways

Gate control mechanism: Gate control mechanism: incoming pain sensations incoming pain sensations must pass through a gate must pass through a gate in the spinal cord that can in the spinal cord that can be open or closed be open or closed (diverted attention can (diverted attention can deflect pain)deflect pain)

Endorphins released Endorphins released through acupuncturethrough acupuncture

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KINESTHESISKINESTHESIS – The – The sense that informs us sense that informs us about the positions and about the positions and motion of parts of our motion of parts of our bodiesbodies

VESTIBULAR SENSEVESTIBULAR SENSE – – The sense of equilibrium The sense of equilibrium (body balance) that (body balance) that informs us about our informs us about our bodies’ positions relative bodies’ positions relative to gravity (semicircular to gravity (semicircular canals) canals) (Your head’s position)(Your head’s position)

Other sensesOther senses

SynesthesiaSynesthesia

http://www.youtube.com/watch?http://www.youtube.com/watch?v=rkRbebvoYqIv=rkRbebvoYqI

Write notes about synethesia…Write notes about synethesia…

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Kangaroo CareKangaroo Care(Gwen 3 weeks old)(Gwen 3 weeks old)

6363Australian Preemie Saved with Kangaroo Care

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PerceptionPerception

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A Changing PictureA Changing Picture

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Defining PerceptionDefining Perception

An active processAn active process The brain pieces The brain pieces

together bits of sensory together bits of sensory information in order to information in order to form orderly impressions form orderly impressions or picturesor pictures

GestaltGestalt 1) Figure-ground1) Figure-ground

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Gestalt Principle #1: Gestalt Principle #1: ProximityProximity

““Meaningful wholes Meaningful wholes seem to precede seem to precede parts and properties, parts and properties, as the Gestalt as the Gestalt psychologists psychologists emphasized years emphasized years ago.” –Anne ago.” –Anne TriesmanTriesman

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Gestalt Principle # 2: Gestalt Principle # 2: SimilaritySimilarity

When similar and When similar and dissimilar objects are dissimilar objects are mingled together, we mingled together, we see the similar see the similar objects as groupsobjects as groups

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Gestalt Principle # 3: Gestalt Principle # 3: ContinuityContinuity

We tend to see We tend to see continuous patterns, continuous patterns, not disrupted onesnot disrupted ones

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Gestalt Principle # 4: Gestalt Principle # 4: SimplicitySimplicity

We perceive the We perceive the simplest shapes simplest shapes possiblepossible

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Gestalt Principle # 5: Gestalt Principle # 5: ClosureClosure

Occurs when people Occurs when people see a familiar pattern see a familiar pattern or shape with some or shape with some missing partsmissing parts

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Perceptual Perceptual InferenceInference

Perceptions are not always based on Perceptions are not always based on sensory informationsensory information

Perceptual Perceptual inferenceinference: occurs when we fill : occurs when we fill in the gaps in what our senses tell usin the gaps in what our senses tell us

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Subliminal PerceptionSubliminal Perception

The Hidden PersuadersThe Hidden Persuaders, Vance Packard, Vance Packard SubSub (below); (below); limenlimen (threshold) (threshold) Subliminal messagesSubliminal messages Congressional and FCC alertsCongressional and FCC alerts

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Subliminal PerceptionSubliminal Perception

The ability to notice The ability to notice stimuli that affect only stimuli that affect only the unconscious mindthe unconscious mind

Controversy and Brian Controversy and Brian Wilson KeyWilson Key

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Subliminal PerceptionSubliminal Perception

The ability to notice The ability to notice stimuli that affect stimuli that affect only the unconscious only the unconscious mindmind

Controversy and Controversy and Brian Wilson KeyBrian Wilson Key

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In the Eye of the In the Eye of the BeholderBeholder

According to Key, According to Key, advertisers routinely advertisers routinely place subliminal place subliminal stimuli in their adsstimuli in their ads

Subliminal self-helpSubliminal self-help

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Two Types Of StimuliTwo Types Of Stimuli

DistalDistal ProximalProximal Developing a Developing a

perceptual perceptual hypothesishypothesis

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Depth PerceptionDepth Perception

The ability to recognize The ability to recognize distance and three-distance and three-dimensional imagesdimensional images

Binocular vs. monocular Binocular vs. monocular cuescues

Retinal disparity and Retinal disparity and convergenceconvergence

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Monocular CuesMonocular Cues

Depth cues about Depth cues about distance are based on distance are based on the image one eye or the the image one eye or the other seesother sees

Six cues: interposition, Six cues: interposition, height in plane, texture height in plane, texture gradient, relative size, gradient, relative size, light and shadow, linear light and shadow, linear perspectiveperspective

Monocular CuesMonocular Cues Linear Perspective—parallel lines Linear Perspective—parallel lines

converging in the distanceconverging in the distance

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Texture Gradient—Closer objects Texture Gradient—Closer objects show more textureshow more texture

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Interposition—nearer objects Interposition—nearer objects mask parts of distant objectsmask parts of distant objects

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Relative Size—Closer objects Relative Size—Closer objects appear to be largerappear to be larger

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Height in plane—The further Height in plane—The further away, the higher the object can away, the higher the object can appear in the frame of viewappear in the frame of view

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Motion Parallax—Closer objects seem to Motion Parallax—Closer objects seem to move faster than more distant objects move faster than more distant objects (like when you are in a car)(like when you are in a car)

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Binocular Cues (using Binocular Cues (using BOTH eyes)BOTH eyes)

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Retinal Disparity: Different images in both Retinal Disparity: Different images in both eyes help with depth perceptioneyes help with depth perception Finger in front of your eyesFinger in front of your eyes

Convergence: Your eyes converge with Convergence: Your eyes converge with closer figurescloser figures Finger in front of your eyesFinger in front of your eyes

Stereograms an exampleStereograms an example

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Optical IllusionsOptical Illusions

Perceptions based on Perceptions based on inappropriate inappropriate assumptions/discrepancassumptions/discrepancy between the y between the appearance of a visual appearance of a visual stimulus and its physical stimulus and its physical realityreality

Muller-Lyer illusionMuller-Lyer illusion

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Another IllusionAnother Illusion Roger Shepard Roger Shepard

(1990)(1990) The Ames The Ames

RoomRoom

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Objects that Objects that can be can be represented in represented in two-two-dimensional dimensional pictures may pictures may not be able to not be able to exist in three-exist in three-dimensional dimensional spacespace

Bottom-up Bottom-up processingprocessing

An Impossible FigureAn Impossible Figure

Perceptual ConstanciesPerceptual Constancies

SizeSize ShapeShape BrightnessBrightness HueHue Location in SpaceLocation in Space

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Shape constancyShape constancy

9595Also, click on picture for moving ball…

Brightness ConstancyBrightness Constancy

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Hue/Color ConstancyHue/Color Constancy

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Perceptual SetPerceptual Set

“Perceptual set” refers to the fact that our perceptions tend to be influenced by our preconceived notions and expectations

Perceptual Set--Perceptual Set--BackmaskingBackmasking

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Two Modes of ProcessingTwo Modes of Processing

Hubel and WieselHubel and Wiesel Bottom-up (see the Bottom-up (see the

parts & then see the parts & then see the whole)whole)

Top-down (We see Top-down (We see someone in the someone in the distance & we fill in distance & we fill in what we don’t see.)what we don’t see.)

Top Down ProcessingTop Down Processing

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Other illusions…Other illusions…

DragonDragon Necker CubeNecker Cube Impossible MotionImpossible Motion DotsDots

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Extrasensory Perception Extrasensory Perception (ESP)(ESP)

The ability to gain information by some The ability to gain information by some means other than the normal sensesmeans other than the normal senses

Paranormal phenomena and Paranormal phenomena and parapsychologyparapsychology

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The “Sixth Sense”The “Sixth Sense”

The major focus includes the following: The major focus includes the following: Telepathy, clairvoyance, precognition, Telepathy, clairvoyance, precognition, and psychokinesisand psychokinesis

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TelepathyTelepathy

Communication of thoughts from one Communication of thoughts from one mind to another that occurs without the mind to another that occurs without the use of our known sensesuse of our known senses

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ClairvoyanceClairvoyance

The ability to perceive objects and events The ability to perceive objects and events without using the senseswithout using the senses

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Precognition and Precognition and PsychokinesisPsychokinesis

Precognition: the ability to foretell the Precognition: the ability to foretell the future future

Psychokinesis: the ability to move objects Psychokinesis: the ability to move objects through mental effort alone through mental effort alone