1. Chapter 3 Sensation andChapter 3 Sensation and
PerceptionPerception
 Sensation occurs when special receptorsSensation occurs when special receptors
in the sense organs are activated, allowingin the sense organs are activated, allowing
various forms of outside stimuli to becomevarious forms of outside stimuli to become
neural signals in the brain. This is calledneural signals in the brain. This is called
TransductionTransduction
 Sensory Receptors- Specialized forms ofSensory Receptors- Specialized forms of
neurons that do not receiveneurons that do not receive
neurotransmitters, but are stimulated byneurotransmitters, but are stimulated by
other forms of energyother forms of energy

2. Sensory ThresholdsSensory Thresholds
 Weber’s Law of Just noticeableWeber’s Law of Just noticeable
difference (JND)- The smallestdifference (JND)- The smallest
difference between two stimuli that isdifference between two stimuli that is
detectable 50% of the timedetectable 50% of the time
– Ex. Add 1 teaspoon to 5 = 1/5 or 20%Ex. Add 1 teaspoon to 5 = 1/5 or 20%
Also 20% of 10 teaspoons it 2/10=1/5Also 20% of 10 teaspoons it 2/10=1/5
Comparisons between 2 stimuliComparisons between 2 stimuli
 Absolute Threshold- Lowest level ofAbsolute Threshold- Lowest level of
stimulation that a person canstimulation that a person can
consciously detect 50% of the time theconsciously detect 50% of the time the
stimulation is presentstimulation is present

3. SensorySensory
Thresholds/Habituation andThresholds/Habituation and
Sensory AdaptationSensory Adaptation
 Subliminal Perception- Stimuli that areSubliminal Perception- Stimuli that are
below the level of conscious awarenessbelow the level of conscious awareness
 Habituation- Tendency of the brain to stopHabituation- Tendency of the brain to stop
noticing constant, unchanging informationnoticing constant, unchanging information
from the ears. Ex. Hum of air conditionerfrom the ears. Ex. Hum of air conditioner
 Sensory Adaptation- Tendency of sensorySensory Adaptation- Tendency of sensory
receptor cells to become less responsive toreceptor cells to become less responsive to
a stimulus that is unchanging.a stimulus that is unchanging.
– Pertains to sight, touch, taste and smellPertains to sight, touch, taste and smell
– Feel of clothes would drive us nuts!Feel of clothes would drive us nuts!

4. Sensory AdaptationSensory Adaptation
 The eyes are different. They are neverThe eyes are different. They are never
that adapted to what we see otherwisethat adapted to what we see otherwise
we would eventually go blind fromwe would eventually go blind from
seeing things so oftenseeing things so often

5. QuizQuiz

6. Sight- PerceptualSight- Perceptual
Properties of LightProperties of Light
 Three aspects to the perception ofThree aspects to the perception of
light:light:
– 1. Brightness- determined by the aptitude1. Brightness- determined by the aptitude
of the wave; how high/low the wave isof the wave; how high/low the wave is
 Higher the wave=brighterHigher the wave=brighter
– 2. Color- determined by the length of the2. Color- determined by the length of the
wavewave
 Long wavelengths= redLong wavelengths= red
– 3. Saturation- purity of the color3. Saturation- purity of the color
determined by the purity of thedetermined by the purity of the
wavelengthswavelengths

7. Structure of the EyeStructure of the Eye
 Cornea- clear membrane that covers theCornea- clear membrane that covers the
eyeeye
– Protects eye and focuses lightProtects eye and focuses light
 Pupil- Iris hole in which light enters the eyePupil- Iris hole in which light enters the eye
 Iris- Muscle that controls the size of pupilIris- Muscle that controls the size of pupil
and how much light enters eyeand how much light enters eye
 Lens- Finishes the focusing processLens- Finishes the focusing process
– As lens hardens, as you age, sight gets worseAs lens hardens, as you age, sight gets worse
 Visual Accommodation- The change in theVisual Accommodation- The change in the
thickness of the lens as the eye changesthickness of the lens as the eye changes
focus on far away/close objectsfocus on far away/close objects

8. Structure of the EyeStructure of the Eye
 Retina- Last stop for light that containsRetina- Last stop for light that contains
3 layers; ganglion cells, bipolar cells3 layers; ganglion cells, bipolar cells
and special cells (photoreceptors)and special cells (photoreceptors)
– Photoreceptors respond to rods andPhotoreceptors respond to rods and
conescones
 Rods- sensory receptors responsible for non-Rods- sensory receptors responsible for non-
color sensitivity to low levels of lightcolor sensitivity to low levels of light
– Found all over the eye except the center-peripheralFound all over the eye except the center-peripheral
visionvision
– All connected to one bipolar cell so the brainAll connected to one bipolar cell so the brain
doesn’t know exactly which rod the signal isdoesn’t know exactly which rod the signal is
coming from so hard to see in low lightcoming from so hard to see in low light

9. Structure of the EyeStructure of the Eye
 Cones- sensory receptors responsible forCones- sensory receptors responsible for
color and sharpness of visioncolor and sharpness of vision
– Found only in center of eyeFound only in center of eye
– Turn photons of light into neuron signals to brainTurn photons of light into neuron signals to brain
– Send signals to bipolar cells that send signals toSend signals to bipolar cells that send signals to
ganglion cellsganglion cells
Light travels through the cornea andLight travels through the cornea and
past the iris, through the pupil and intopast the iris, through the pupil and into
the lens and on to the retina where it isthe lens and on to the retina where it is
transformed into nerve impulsestransformed into nerve impulses

10. How the Eye WorksHow the Eye Works
 Dark Adaptation- Eye recovers it’s ability toDark Adaptation- Eye recovers it’s ability to
see when going from very bright to darksee when going from very bright to dark
– The brighter the light the longer toThe brighter the light the longer to
readapt to darkreadapt to dark
– As person gets older longer it takes toAs person gets older longer it takes to
adapt to darkadapt to dark
– Rods adapt to dark, but do not seeRods adapt to dark, but do not see
sharplysharply
 Light Adaptation- Recovery of eye’sLight Adaptation- Recovery of eye’s
sensitivity to light after being in the darksensitivity to light after being in the dark
– Cones adapt to lightCones adapt to light

11. Perception of ColorPerception of Color
 How people see colorHow people see color
– Trichromatic Theory- Three types ofTrichromatic Theory- Three types of
cones; red, blue and greencones; red, blue and green
– The combinations of cones and rates atThe combinations of cones and rates at
which the neurons are fired determine thewhich the neurons are fired determine the
colorscolors
– Afterimage- vision of an object is stillAfterimage- vision of an object is still
seen after the object is removed fromseen after the object is removed from
sight, though the colors are all wrong!sight, though the colors are all wrong!
 Flag experimentFlag experiment

12. Perception of ColorPerception of Color
 Opponent-Process theory- FourOpponent-Process theory- Four
primary colors with cones arranged inprimary colors with cones arranged in
pairs; red-green and yellow-bluepairs; red-green and yellow-blue
– If one color is stimulated the other is notIf one color is stimulated the other is not
working: when one color is seen a lot itworking: when one color is seen a lot it
tires out so the other can take overtires out so the other can take over

13. Color BlindnessColor Blindness
 3 kinds of color blindness3 kinds of color blindness
– Monochrome= either have no cones or theMonochrome= either have no cones or the
cones do not workcones do not work
 See only shades of graySee only shades of gray
– Red-green= either red or green cones do notRed-green= either red or green cones do not
workwork
– Blue= blue cones do not work only see red,Blue= blue cones do not work only see red,
green and graygreen and gray
 More men are color blind than womenMore men are color blind than women
 Color blindness is recessiveColor blindness is recessive
 Men only need one recessive geneMen only need one recessive gene
 Y chromosome does not have the gene that preventsY chromosome does not have the gene that prevents
colorblindnesscolorblindness
 Women need two recessive genesWomen need two recessive genes

14. QuizQuiz

15. Hearing-Perception ofHearing-Perception of
SoundSound
 Sound waves are the vibrations ofSound waves are the vibrations of
molecules of airmolecules of air
 Have the same properties as light wavesHave the same properties as light waves
 Wavelengths are interpreted as frequencyWavelengths are interpreted as frequency
or pitchor pitch
 Amplitude is interpreted as volumeAmplitude is interpreted as volume
 Purity is interpreted as timbre (pure tones)Purity is interpreted as timbre (pure tones)
 Frequency is measured in Hertz (Hz)Frequency is measured in Hertz (Hz)
 Most accurate hearing is at 1,000 HzMost accurate hearing is at 1,000 Hz

16. Structure of the EarStructure of the Ear
 Outer EarOuter Ear
– Pinna is the outside of the ear that funnels soundPinna is the outside of the ear that funnels sound
– Pinna is entrance to auditory canal (ear canal)Pinna is entrance to auditory canal (ear canal)
that leads to eardrumthat leads to eardrum
– Tiny bones vibrate sound waves hit themTiny bones vibrate sound waves hit them
 Middle Ear (Hammer, Anvil, & Stirrup)Middle Ear (Hammer, Anvil, & Stirrup)
– The three tiny bones are; hammer, anvil & stirrupThe three tiny bones are; hammer, anvil & stirrup
– Named for the shapes of the bonesNamed for the shapes of the bones
– Stirrup vibrates a membrane covering theStirrup vibrates a membrane covering the
opening to the inner earopening to the inner ear

17. Structure of the EarStructure of the Ear
 Inner Ear (Oval window)Inner Ear (Oval window)
– Cochlea-snail shaped structure filled withCochlea-snail shaped structure filled with
fluid that vibratesfluid that vibrates
– Basilar membrane- in the middle of theBasilar membrane- in the middle of the
cochlea that houses the organ of corticochlea that houses the organ of corti
– Organ of corti contains receptor cells forOrgan of corti contains receptor cells for
hearinghearing
– Sound waves go through pinna, vibrateSound waves go through pinna, vibrate
the eardrum, vibrates the hammer, anvilthe eardrum, vibrates the hammer, anvil
& stirrup, vibrates the oval window, fluid& stirrup, vibrates the oval window, fluid
in cochlea vibrates, basilar membranein cochlea vibrates, basilar membrane
vibrates, Corti bends hair cells, signalvibrates, Corti bends hair cells, signal
sent to brain.sent to brain.

18. Structure of the EarStructure of the Ear
 Louder the sound=stronger theLouder the sound=stronger the
vibrations=stimulates more hairvibrations=stimulates more hair
cells=sound interpreted as loudcells=sound interpreted as loud

19. Theories of PitchTheories of Pitch
 Pitch- how low or high a sound isPitch- how low or high a sound is
 Place theory- the pitch a person hearsPlace theory- the pitch a person hears
depends on where the hair cells thatdepends on where the hair cells that
are stimulated areare stimulated are
 Frequency theory- Pitch depends onFrequency theory- Pitch depends on
how fast the basilar membranehow fast the basilar membrane
vibrates; slow=lowvibrates; slow=low
 Both theories are correctBoth theories are correct
– Place theory=above 1,000 HzPlace theory=above 1,000 Hz
– Frequency theory=below 100 HzFrequency theory=below 100 Hz

20. Theories of PitchTheories of Pitch
 Volley Principal= After 100 Hz theVolley Principal= After 100 Hz the
auditory neurons take turns firingauditory neurons take turns firing
 If sound is at 300 Hz there are 3If sound is at 300 Hz there are 3
groups of neurons at 100 Hz eachgroups of neurons at 100 Hz each

21. Types of HearingTypes of Hearing
ImpairmentsImpairments
 Conduction Hearing Impairment-Conduction Hearing Impairment-
Sound not passed from eardrum toSound not passed from eardrum to
cochlea= damage to eardrum/bones-cochlea= damage to eardrum/bones-
hearing aid may helphearing aid may help
 Nerve Hearing Impairment-Nerve Hearing Impairment-
– Inner ear, auditory pathways, or corticalInner ear, auditory pathways, or cortical
areas are damaged.areas are damaged.
– Aging, or exposure to loud noisesAging, or exposure to loud noises
– Damage to the hair cells in the cochlea.Damage to the hair cells in the cochlea.
– Tinnitus – ringing in one’s earsTinnitus – ringing in one’s ears