SensationSensation

Psychology 1106Psychology 1106

IntroductionIntroduction

►To talk to someone we have to hear To talk to someone we have to hear what they saywhat they say

►To catch a ball, we have to see it comingTo catch a ball, we have to see it coming►How does the external get internalizedHow does the external get internalized

That in essence, is what sensation isThat in essence, is what sensation is

►Bottom up vs. Top down processingBottom up vs. Top down processing Sensation is bottom upSensation is bottom up Perception is top downPerception is top down

Basic PrinciplesBasic Principles

►ThresholdsThresholds We sense some things and not othersWe sense some things and not others Faintest stimuliFaintest stimuli

►Absolute thresholdAbsolute threshold

Difference thresholds or jndsDifference thresholds or jnds►ProportionProportion►Stimuli must differ by a constant proportion to Stimuli must differ by a constant proportion to

be seen as differentbe seen as different Weber’s LawWeber’s Law

Signal Detection TheorySignal Detection Theory

►When will we detect stimuli?When will we detect stimuli?►Have to filter out the background noiseHave to filter out the background noise

Can be internal or externalCan be internal or external

►Hits vs. missesHits vs. misses►False alarms vs. rejectionsFalse alarms vs. rejections

What about subliminal What about subliminal messages?messages?

► ““listen to these tapes, they are only 499.95’listen to these tapes, they are only 499.95’►We don’t know what the stimulus is, and, it We don’t know what the stimulus is, and, it

can affect our behaviour for a brief periodcan affect our behaviour for a brief period►Does it make us buy coke?Does it make us buy coke?

NO NO NO NO NONO NO NO NO NO►CBC ExperimentCBC Experiment►WTWO experimentWTWO experiment►http://www.snopes.com/business/hidden/popcorn.asphttp://www.snopes.com/business/hidden/popcorn.asp

What about backward masking…What about backward masking…►Umm, noUmm, no

Sensory adaptationSensory adaptation

►Getting used to somethingGetting used to something► If you stop your eyes from moving, If you stop your eyes from moving,

everything would go grey!everything would go grey!►Same thing if you give them constant Same thing if you give them constant

stimulation, the ping pong ball trickstimulation, the ping pong ball trick►Ever notice how everybody else’s Ever notice how everybody else’s

house smells funny and yours has no house smells funny and yours has no smell at all?smell at all?

VisionVision

►Like any sensory process, vision Like any sensory process, vision converts some energy to neural converts some energy to neural messagesmessages

► In this case, light In this case, light ►Light is just a form of electromagnetic Light is just a form of electromagnetic

radiationradiation►So are x rays, micro waves, infra red, So are x rays, micro waves, infra red,

UV cosmic rays etcUV cosmic rays etc

I wish to hell I could see I wish to hell I could see better….better….

►Wavelength of light determines hueWavelength of light determines hue► Intensity determines brightnessIntensity determines brightness►Light enters the eye through the Light enters the eye through the

cornea and the pupilcornea and the pupil►Pupil size regulated by irisPupil size regulated by iris►Behind pupil, lens, which accomodatesBehind pupil, lens, which accomodates►Light hits the retinaLight hits the retina►Oh ya, it is upside down….Oh ya, it is upside down….

AcuityAcuity

► Acuity is affected by Acuity is affected by the shape of the the shape of the eyeeye

►Nearsighted, eye Nearsighted, eye too long, or cornea too long, or cornea too curvedtoo curved

► So far away stuff is So far away stuff is blurryblurry

► Image is in front of Image is in front of the retinathe retina

► Farsighted, oppositeFarsighted, opposite

The retinaThe retina

► There are two kinds of There are two kinds of receptors in the retina, receptors in the retina, rods and conesrods and cones

► Rods for night, Rods for night, brightnessbrightness

► Cones for day, colourCones for day, colour► When a photon hits a When a photon hits a

receptor it sends a receptor it sends a message via the optic message via the optic nerve to the brainnerve to the brain

► Because of this, we Because of this, we have a blind spot!have a blind spot!

Gotta love the retinaGotta love the retina

►Cones are for fine detail and colourCones are for fine detail and colour►Cones only really work in the lightCones only really work in the light►Concentrated in the foveaConcentrated in the fovea►Rods are more evenly distributedRods are more evenly distributed►Many rods to one bipolar cell, so you Many rods to one bipolar cell, so you

can see in dim light, but only in black can see in dim light, but only in black and whiteand white

►One rod, one bipolar cellOne rod, one bipolar cell►About 130 000 000 receptors per retinaAbout 130 000 000 receptors per retina

Its all about me….Its all about me….

►There are disorders that can lead to There are disorders that can lead to problems for the retinaproblems for the retina

►AlbinismAlbinism►Pigment guides growth of visual Pigment guides growth of visual

systemsystem► I have no foveaI have no fovea►My eyes are wired ipsilaterallyMy eyes are wired ipsilaterally

And now we leave the eye..And now we leave the eye..

► Further up the system Further up the system there are feature there are feature detectorsdetectors

► Hubel and Wiesel and Hubel and Wiesel and cats and Swedish Kingscats and Swedish Kings Cells in cortex that Cells in cortex that

respond to different line respond to different line orientationorientation

Truly cool, maybe they Truly cool, maybe they network together to network together to recognize objects?recognize objects?

More Feature DetectorsMore Feature Detectors

► Dave Perrett’s work on Dave Perrett’s work on face recognition in face recognition in monkeysmonkeys

► Monkeys have cells in Monkeys have cells in their cortex that respond their cortex that respond only to a specific only to a specific monkey!monkey!

► Sort of like one of those Sort of like one of those ‘Grandmother’ cells.‘Grandmother’ cells. Probably a hierarchical Probably a hierarchical

networknetwork Hughlings-Jackson PrincipleHughlings-Jackson Principle

►Processing has to be parallelProcessing has to be parallel► Imagine doing it serially!Imagine doing it serially!►130 000 000 receptors, one after the 130 000 000 receptors, one after the

otherother►You probably wouldn’t live long You probably wouldn’t live long

enough to recognize a triangleenough to recognize a triangle►The ability to process in this fashion The ability to process in this fashion

could be blown out by a strokecould be blown out by a stroke

Colour visionColour vision

►Trichromatic theoryTrichromatic theory►Opponent process theoryOpponent process theory►Three types of conesThree types of cones

Red-greenRed-green Blue-yellowBlue-yellow Black-whiteBlack-white

►Explains afterimagesExplains afterimages

► Stare at this Stare at this

Colour constancyColour constancy

►Weird thing is that we see things as Weird thing is that we see things as having the same colour even if they having the same colour even if they move in to different light conditionsmove in to different light conditions

►So a gold coin, reflecting blue light, So a gold coin, reflecting blue light, still looks goldstill looks gold

►More of a perceptual thing than More of a perceptual thing than anything elseanything else

HearingHearing

► Just like vision, we are Just like vision, we are converting one form converting one form of energy to anotherof energy to another

► Sound is just changes Sound is just changes in air pressurein air pressure

► Sound pressure levelSound pressure level► dBdB► 100 dB is 10 times 100 dB is 10 times

louder than 90 dBlouder than 90 dB

The EarThe Ear

► Outer ear sort of sucks Outer ear sort of sucks sound in towards the sound in towards the eardrumeardrum

► Middle er transmits Middle er transmits vibrations from the vibrations from the eardrum to hammer, eardrum to hammer, anvil and stirrupanvil and stirrup

► Gets to the snail Gets to the snail shaped cochlea in the shaped cochlea in the inner earinner ear

► Fluid vibratesFluid vibrates► Movement detected by Movement detected by

hair like projections on hair like projections on the basilar membranethe basilar membrane

PitchPitch

► Frequency of soundFrequency of sound► Place theoryPlace theory

Different frequencies make different parts of the Different frequencies make different parts of the membrane vibratemembrane vibrate

High frequencies, start of cochleaHigh frequencies, start of cochlea Hmm, low frequencies are less localizedHmm, low frequencies are less localized

► Frequency theoryFrequency theory Frequency of vibrations?Frequency of vibrations? But how do we hear over 1000 Hz?But how do we hear over 1000 Hz?

► Probably bothProbably both

Sound LocalizationSound Localization

►Sounds hit ears at different times, with Sounds hit ears at different times, with different volumesdifferent volumes

►So left right distinction is really pretty So left right distinction is really pretty easyeasy

►Up down is VERY hard, if not Up down is VERY hard, if not impossibleimpossible

►We usually do up down in concert with We usually do up down in concert with other sensesother senses

Other sensesOther senses

►TouchTouch PressurePressure WarmthWarmth ColdCold PainPain

►Pressure is easy to understand, 1 to 1 Pressure is easy to understand, 1 to 1 relationshiprelationship

►There are more receptors some places There are more receptors some places than other placesthan other places

Come on come on come on Come on come on come on come on and touch me babycome on and touch me baby

►PainPain Probably a gate that selectively blocks Probably a gate that selectively blocks

painpain StimulationStimulation Cognitive effectsCognitive effects

►Strangely enough there are different Strangely enough there are different receptors for cold and warmthreceptors for cold and warmth

TasteTaste

►Sweet Sweet ►SourSour►BitterBitter►SaltySalty►UnamiUnami►Carbohydrate?Carbohydrate?►Makes lots of evolutionary senseMakes lots of evolutionary sense►Need the interaction with smell and Need the interaction with smell and

visionvision