Sensation & Sensation & PerceptionPerception

Unit 3Unit 3

Chapter 4Chapter 4

SensationSensation

Stimulation of sensory receptors and Stimulation of sensory receptors and transmission of sensory info to the transmission of sensory info to the central nervous system (spinal central nervous system (spinal cord/brain)cord/brain)– Sensory receptorsSensory receptors– Stimulation automaticStimulation automatic– Presence of chemicalsPresence of chemicals

Absolute ThresholdAbsolute Threshold

WeakestWeakest amount of amount of stimulus that can stimulus that can be sensedbe sensed

Vision, hearing, Vision, hearing, smell, taste, touchsmell, taste, touch

Differ from person Differ from person to personto person– Psychological Psychological

factorsfactors– Biological factorsBiological factors

Examples of Absolute Examples of Absolute ThresholdsThresholds

Sense Absolute Threshold

VisionVision A candle flame seen at 30 miles on a dark clear A candle flame seen at 30 miles on a dark clear nightnight

HearingHearing The tick of a watch under quiet conditions at 20 The tick of a watch under quiet conditions at 20 feetfeet

TasteTaste One teaspoon of sugar in two gallons of waterOne teaspoon of sugar in two gallons of water

SmellSmell One drop of perfume diffused into entire volume of One drop of perfume diffused into entire volume of a six room apartmenta six room apartment

TouchTouch The wing of a fly falling on your cheek from a The wing of a fly falling on your cheek from a distance of 1 centimeterdistance of 1 centimeter

Difference ThresholdDifference Threshold

Minimum amount of difference detected Minimum amount of difference detected between 2 stimuli between 2 stimuli

Signal-Detection TheorySignal-Detection Theory

Method for distinguishing sensory Method for distinguishing sensory stimuli that accounts for stimuli stimuli that accounts for stimuli strengths, strengths, andand setting, your physical setting, your physical state, your mood, your attitudestate, your mood, your attitude

Also considers psychological factorsAlso considers psychological factors– MotivationMotivation– ExpectationsExpectations– LearningLearning

PerceptionPerception

Psychological process through which Psychological process through which we interpret sensory stimulationwe interpret sensory stimulation

Reflects learning, expectations, Reflects learning, expectations, attitudesattitudes

Way in which we organize our Way in which we organize our sensory informationsensory information

ClosureClosure Tendency to Tendency to

perceive a perceive a complete or whole complete or whole figure even when figure even when there are there are gapsgaps in in what your senses what your senses tell youtell you

Fill in the blanksFill in the blanks

Ground-Figure PerceptionGround-Figure Perception

Figures against a Figures against a backgroundbackground

What we perceive What we perceive as figure and what as figure and what we perceive as we perceive as background background influence our influence our perceptionperception

ProximityProximity

Group together Group together events that are events that are near each othernear each other

Things which are Things which are close togetherclose together are seen as are seen as belonging togetherbelonging together

ContinuityContinuity

Perceive things as belonging together if Perceive things as belonging together if they form some type of they form some type of continuouscontinuous pattern pattern

SimilaritySimilarity

Occurs when Occurs when objects look objects look similarsimilar to one to one anotheranother

See groups which See groups which have the have the same same characteristicscharacteristics

Common FateCommon Fate

Tendency to perceive objects that are Tendency to perceive objects that are moving together as belonging togethermoving together as belonging together

Depth PerceptionDepth Perception

Monocular CuesMonocular Cues Need only Need only one eyeone eye to to

be perceivedbe perceived Cause certain objects Cause certain objects

to appear more to appear more distant from the distant from the viewer than othersviewer than others

pictorial depth cuespictorial depth cues- -

clues about distance given clues about distance given in a flat picturein a flat picture

Binocular CuesBinocular Cues Visual cues for depth Visual cues for depth

that require the use for that require the use for both eyesboth eyes

retinal disparity-retinal disparity- images projected to images projected to different locations on different locations on right and left retinasright and left retinas

convergence-convergence- sensing the eyes sensing the eyes converging toward converging toward each other as they each other as they focus on closer objectsfocus on closer objects

Stroboscopic MotionStroboscopic Motion

illusion of movementillusion of movement rapid progression of images or rapid progression of images or

objects not moving at allobjects not moving at all our perceptionsour perceptions

fill in the gapsfill in the gaps

Stroboscopic PhotographyStroboscopic Photography

VisionVision

Unit 2.2Unit 2.2

The Human EyeThe Human Eye

• cornea-cornea- transparent transparent tissue where light tissue where light enters the eyeenters the eye

• pupilpupil- opening in - opening in center of iris that center of iris that allows light to pass allows light to pass into the eyeinto the eye

• irisiris- controls pupil - controls pupil sizesize

• lens-lens- focuses the focuses the light rays on the light rays on the retinaretina

• retina-retina- contains contains sensory receptors sensory receptors that process visual that process visual information and information and send it to the brainsend it to the brain

• optic nerve-optic nerve- carries carries visual info to brainvisual info to brain

Near + FarNear + Far

• NearsightednessNearsightedness– Close objects are Close objects are

seen clearly but seen clearly but distant objects distant objects appear blurryappear blurry

– Eyeball is too Eyeball is too longlong

• FarsightednessFarsightedness– Distant objects seen Distant objects seen

clearly but close clearly but close objects appear objects appear blurryblurry

– Eyeball is too Eyeball is too shortshort

Rods and ConesRods and Cones

• 2 kinds of 2 kinds of photoreceptorsphotoreceptors– Neurons that are Neurons that are

sensitive to lightsensitive to light

• Rods Rods are sensitive are sensitive to only to only brightnessbrightness – Allow us to see Allow us to see

black/whiteblack/white

• ConesCones provide provide color visioncolor vision

Dark and Light AdaptationDark and Light Adaptation

• Dark-Dark- adjustment to lower lighting adjustment to lower lighting– Continues to improve for up to 45 Continues to improve for up to 45

minutesminutes

• LightLight- adjustment to bright lighting- adjustment to bright lighting– Occurs within minutesOccurs within minutes

Visual AcuityVisual Acuity

• Sharpness of Sharpness of visionvision

• Determined by Determined by ability to see ability to see visual detailsvisual details

Color VisionColor Vision

• Cones enable us to perceive colorCones enable us to perceive color– Sensitive to blue, green, redSensitive to blue, green, red

• Multi cone stimulation allows for Multi cone stimulation allows for other colors to be seenother colors to be seen– Other colors are created through Other colors are created through

combinations of red, blue, greencombinations of red, blue, green

Color ComplimentColor Compliment

• AfterimageAfterimage of a color is its of a color is its complimentary colorcomplimentary color

Color BlindnessColor Blindness• People who don’t have normal color People who don’t have normal color

visionvision

• Partially or totally unable to distinguish Partially or totally unable to distinguish colorcolor– Malfunction of conesMalfunction of cones

• Total color blindness is rareTotal color blindness is rare– Sensitive to only light and darkSensitive to only light and dark

• Partial color blindness is more commonPartial color blindness is more common– See red green but have hard time See red green but have hard time

distinguishing between the twodistinguishing between the two

Depth PerceptionDepth Perception

Monocular CuesMonocular Cues

• Need only Need only one eyeone eye to be perceivedto be perceived

• Cause certain objects Cause certain objects to appear more to appear more distant from the distant from the viewer than othersviewer than others

• Perspective, Perspective, clearness, shadowclearness, shadow

Binocular CuesBinocular Cues

• Visual cues for depth Visual cues for depth that require the use that require the use for for both eyesboth eyes

• retinal disparity- retinal disparity- depth of an objectdepth of an object

• convergence-convergence- both both eyes focus on the eyes focus on the same objectsame object

HearingHearing

Unit 2.4Unit 2.4

https://www.youtube.com/watch?v=flIAxGsV1q0

The EarThe Ear

Outer ear-Outer ear- collects collects and sends sounds to and sends sounds to the eardrumthe eardrum

Cochlea-Cochlea- transforms transforms sound vibrations to sound vibrations to auditory signalsauditory signals

Auditory nerve-Auditory nerve- transmits neural transmits neural impulses to brainimpulses to brain

DeafnessDeafness

ConductiveConductive damage to middle damage to middle

earear Affects sound Affects sound

amplificationamplification Can be corrected Can be corrected

with hearing aidswith hearing aids

SensorineuralSensorineural Damage to inner ear, Damage to inner ear,

auditory nerveauditory nerve Absence of sound Absence of sound

perception for certain perception for certain frequenciesfrequencies

““artificial ear” artificial ear”

Other SensesOther Senses

Unit 2.5Unit 2.5

https://www.youtube.com/watch?v=EJud8MKrvBE

SmellSmell

Essential to tasteEssential to taste Odors are detected by receptor neurons Odors are detected by receptor neurons

in nostrilsin nostrils React when molecules come into contact React when molecules come into contact

with themwith them Send information about odor to brain via Send information about odor to brain via

olfactory nerveolfactory nerve

Adapts quicklyAdapts quickly

TasteTaste Sweet, sour, salty, bitterSweet, sour, salty, bitter Flavor of food is more complex than tasteFlavor of food is more complex than taste

Odor, texture, temperature, tasteOdor, texture, temperature, taste

Receptors on taste buds of tongueReceptors on taste buds of tongue Sensitivity to different tastes can be Sensitivity to different tastes can be

inheritedinherited Bitter = “taste blind”Bitter = “taste blind”

Taste cells reproduce rapidlyTaste cells reproduce rapidly

https://www.youtube.com/watch?v=kyrIxAXZISc

Skin Senses (Touch)Skin Senses (Touch)

Combination of pressure, temperature, Combination of pressure, temperature, painpain Distinct sensory receptors Distinct sensory receptors Receive more than one type of sensory inputReceive more than one type of sensory input

PressurePressure Sensory receptors (pacinian corpuscle) Sensory receptors (pacinian corpuscle)

located around the roots of hair cellslocated around the roots of hair cells Fire where skin is touchedFire where skin is touched

Different parts of body more sensitiveDifferent parts of body more sensitive moremore = fingertips, lips, nose, cheeks = fingertips, lips, nose, cheeks less less = shoulders, thighs, calves= shoulders, thighs, calves

Rapidly adaptsRapidly adapts

PainPain Receptors located all Receptors located all

over bodyover body Not all equally sensitive Not all equally sensitive

to painto pain

prostaglandinsprostaglandins- help - help body transmit pain body transmit pain messages to brainmessages to brain

Can experience pain in Can experience pain in limbs no longer there = limbs no longer there = “phantom limb”“phantom limb”

Message sentto spinal cordto thalamus

in brain

Projected tocerebral cortex

where registration of

severity/locationof pain is

determined

Pain originates at the point of contact

https://www.youtube.com/watch?v=1mHIv5ToMTM

The Gate Theory of PainThe Gate Theory of PainOnly a certainOnly a certain

amount of amount of informationinformation

can be processedcan be processed by the by the

nervous system nervous system at one timeat one time

Different sensationsDifferent sensationscompete withcompete with

pain messagespain messagesfor attentionfor attention

Neurons Neurons

cant get cant get

pain messages pain messages

to brainto brain

“Flooding” preventsmany or all

messages fromgetting through

Body SensesBody Senses VestibularVestibular- position of the - position of the bodybody

sensory organs located in the earssensory organs located in the ears Enables balanceEnables balance

KinesthesisKinesthesis- position and movement of - position and movement of individual body partsindividual body parts Sensory organs in joints, tendons, musclesSensory organs in joints, tendons, muscles