Sensation

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Sensation

• Objectives
• 1.  Contrast the processes of sensation and
  perception.
• 2.  Distinguish between absolute and difference
  thresholds, and discuss research findings on
  subliminal stimulation.
• 3.  Describe the phenomenon of sensory adaptation
  and explain its functional value.

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Sensation

• Sensation
• Sensation- process of detecting physical energy
  from the environment and encoding it into neural
  signals
• -done by our sensory organs
• Perception
• process of selecting, organizing, and
  interpreting our sensations
• -done by our brains

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Sensation

• Our sensory and perceptual processes work
  together to help us sort out complex
• processes

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Sensation

• Bottom-Up Processing
• processing that begins with the sense receptors
  and works up to the brains integration of
  sensory information
• Top-Down Processing
• information processing guided by higher-level
  mental processes
• as when we construct perceptions drawing on our
  experience and expectations

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Sensation- Basic Principles

• -as humans we exist in a sea of energy
• -some we are aware of, some we arent
• psychophysics-the study of how this physical
  energy around us relates to our psychological
  experience
• ltltEARLY SCHOOL OF PSYCHOLOGYgtgt

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Sensation- Thresholds

• Absolute Threshold
• minimum stimulation needed to detect a particular
  stimulus 50 of the time
•  

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Sensation- Thresholds

• vision-we can see a candle flame from 30 miles on
  a clear, dark night (granted there are no
  physical
• obstructions)
•  hearing-we can hear a watch ticking in a silent
  room from 20 feet away
•  touch- we can feel the wing of a fly falling on
  our face from a very close distance
•  smell-we can smell a single drop of perfume in a
  3 room apartment
• taste-we can taste a teaspoon of sugar diluted in
  2 or 3 gallons of water
•   ex. Hearing tests

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Sensation- Thresholds

• Signal Detection Theory
• predicts how and when we detect the presence of a
  faint stimulus (signal) amid background
  stimulation (noise)
• assumes that there is no single absolute
  threshold
• detection depends partly on persons
• Experience/ expectations/ motivation/ level of
  fatigue
• gtseeks to explain why people respond differently
  to the same stimuli, and why the same persons
  reactions vary as circumstances change

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Sensation- Thresholds

• Difference Threshold
• minimum difference between two stimuli required
  for detection 50 of the time
• -aka the just noticeable difference (jnd) 
• -the difference threshold increases with the
  magnitude of the stimulus
•  

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Sensation- Thresholds

• Webers Law- to perceive as different, two
  stimuli must differ by a constant minimum
  percentage (rather than amt)
• light intensity- 8
• weight- 2
• tone frequency- 0.3
• Sensory adaptation- diminished sensitivity as a
  consequence of constant stimulation
• Why??

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Sensation- Subliminal Stimulation

• subliminal message- stimulus that lies below
  ones absolute threshold for conscious awareness
• We can detect some subliminal messages
• How is that?
• -because absolute thresholds involve
• detecting the stimulus 50 of the time
• Does this mean we can be subliminally persuaded?
  
• ltltNOgtgt
• gtgtCBC Sunday night Study..Telephone Now
• gtgtsubliminal tape study
• gtgtJohn Krosnick 1992

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Sensation- Thresholds

• Subliminal
• When stimuli are below ones absolute threshold
  for conscious awareness

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Vision- Stabilized Images on the Retina
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Vision

• 4.  Explain the visual process, including the
  stimulus input, the structure of the eye, and the
  transduction of light energy.
• Describe the 2 major theories of color vision.
• Explain issues with visual acuity and examine the
  afterimage effect in the context of opponent
  process theory.

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Vision

• Transduction-process by which our sensory systems
  convert stimulus energy into neural messages
• A.        The Stimulus for Vision
• light
• travels in electromagnetic waves
• we only see visible portion of the light spectrum
• ROY G. BIV
• 2 physical characteristics of light that
  determine our sensory experience of them
• 1.        wavelength-distance from one wave
• peak to the next
• det frequency
• determines the hue-color
• 2.  amplitude-height of wave
• determines the intensity or brightness of the
  wave

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The spectrum of electromagnetic energy
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Vision- Physical Properties of Waves
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Vision- The Eye

• light enters through the cornea (a transparent
  protector- bends light)
• pupil small adjustable opening of the eye
  determines the amount of light let in (black part
  of eye)
• Iris-muscle that controls the amt of light that
  enters the pupil (colored pt of eye)
• lens -behind the pupil
• it focuses light rays by adjusting its curvature
  process known as accommodation
• lens focus light onto the retina -the light
  sensitive inner surface of our eyes

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Vision- The Eye

• Retina contains photoreceptors (rods and cones)
  which convert light energy into neural impulses
  ltltpt of transduc in visgtgt
• these impulses carried by optic nerve to the
  brain where they are constructed into full images
  
• Rods-detect black, white, and gray
• necessary for peripheral and twilight vision
• Cones-detect fine-detail and give rise to color
  sensations
• concentrated around center of retina (fovea
  central point of focus)
• gtgtexp why the pupil must open to see in dark-b/c
  rods are on the periphery of retina

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Vision

• Cones-6 million
• Rods-120 million
• We can see fine detail in color but can see black
  and white better in dim lightwhy?
• Enter bipolar cells
• Cones many have their own bipolar cells
  assigned to them (more specific info transmitted)
• Rods-share bipolar cells so many can team up and
  pool their energy to transmit in dim light

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Vision- Receptors
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Vision

• when light strikes the rods and cones of the
  retina it causes a reaction that stimulates the
  optic nerve
• nerve that carries neural impulses from the eye
  to the brain
• blind spot-the area where the optic nerve leaves
  the eye is devoid of photoreceptors
• P 203 figure 5.8

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Vision
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Pathways from the Eyes to the Visual Cortex
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Vision

• Acuity- the sharpness of vision
• Nearsightedness- nearby objects seen more clearly
  than distant objects because distant objects in
  front of retina
• Farsightedness- faraway objects seen more clearly
  than near objects because the image of near
  objects is focused behind retina

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Vision

• Far Nearsighted Normal
  (Short eyeball) (Long eyeball)

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Visual Information Processing

• Feature Detectors (David Hubel Torsten Wiesel
  1979)
• nerve cells in the brain that respond to specific
  features
• shape
• angle
• Movement
• Facial Recognition 30 of cortex
• Temporal Lobe involved in facial recog (see p
  205)

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Visual Information Processing
FYI-Facial rec 30 of cortex (temp lobe heav
inv) Sensorimotor skills far more

• Parallel Processing
• simultaneous processing of several aspects of a
  problem simultaneously
• gtgtBrain divides visual scene into subdivisions
• gtThey are all processed in parallel and combined
  into a whole.

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Young and HelmholtzsTrichromatic (three
color) Theory

• three different retinal color receptors
• Red, green,Blue
• When combinations are stimulated, we see other
  colors

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Color-Deficient Vision

• People who suffer red-green blindness lack
  functioning red or green sensitive cones
• Well if Yellow is a mix of green red, then how
  can c.b. see yellow?
• Enter Ewald Herings Opponent Process Theory

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Visual Information Processing

• Ewald Herings Opponent-Process Theory- opposing
  retinal processes enable color vision
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black
• Neurons in the retina thalamus turned on by one
  of these colors are turned off by the opposite
  color
• Why we cannot see greenish red

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Afterimage Effect-explained by Opp Proc Th
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Visual Information Processing

• Color Constancy
• Perceiving familiar objects as having consistent
  color, even if changing illumination alters the
  wavelengths reflected by the object
• Color Sensation is a Subjective experience
  context plays a role in the process
• Ex. apple in fruit bowl color remains constant
  as lighting shifts

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Audition

• 7.  Explain the auditory process, including the
  stimulus input and the structure and function of
  the ear.
• 8.  Explain the place and frequency theories of
  pitch perception, and describe how we locate
  sounds.
• 9.  Discuss the nature and causes of hearing
  loss, and describe the effects of noise on
  hearing and behavior.

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Audition

• -audition-sense of hearing
• Sound Waves
• -our ears detect changes in air pressure caused
  by sound waves and transform them into neural
  impulses that our brains decode as sounds
• -amplitude/height determines the loudness
  (measured in decibels)
• Abs Threshold defined as 0 dB
• Every 10 decibel increase represents a tenfold
  increase in so
• -prolonged exposure gt 85 decibels hearing loss
  (sensorineural) -- Rock Concerts 140 dB

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The Intensity of Some Common Sounds
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Audition

• frequency-(the of wavelengths that pass a point
  per second) determines Pitch
• pitch a tones highness or lowness
• longer the wave/lower the frequency/lower the
  pitch
• shorter the wave/higher the frequency/higher the
  pitch
• (1 cycle/ sec 1 Hz humans detect 20-20k Hz)
• Volume-det by amplitude

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Audition- The Ear

• Outer Ear
• the visible part--
• channels sound waves through the auditory canal
  to the eardrum(gateway to the middle ear)

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Audition- The Ear

• Middle Ear
• Conducts eardrums vibrations through the hammer,
  anvil, and stirrup(smallest bone in body), which
  in turn stimulate the cochlea
• Inner Ear (cochlea, semicircular canals,
  vestibular sacs)
• contains the cochlea-a coiled, bony, fluid-filled
  tube, which triggers nerve impulses
• cochlea contains the basilar membrane which is
  lined with tiny hair cells (16k v 130 mil
  rods/cones)
• -when the fluid in the cochlea vibrates -it
  stimulates these hair cells which triggers
  impulse in adjacent nerve fibers, which connect
  to the auditory nerve (TRANSDUCTION)

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Pitch Perception

• Place Theory (Herman von Helmholtz)
• pitch we hear is det by place where the cochleas
  membrane is stimulated (place of vib det pitch)
• Hi freq waves produce large vib near beg of
  cochleas membrane low near end
• gtgtbrain can det pitch by recog place on membrane
  from which it receives neural signals
• Problem Low pitched sounds dont neatly localize
  on basilar membrane
• Enter Frequency Theory
• the theory that the rate of nerve impulses
  traveling up the auditory nerve matches the
  frequency of a tone, thus enabling us to sense
  its pitch

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Pitch Perception

• Frequency Theory Contd
• Brain reads pitch from frequency of neural
  impulses b/c neural impulses are triggered at
  same rate as sound wave(100 waves/ sec 100
  pulses/ sec)
• (note humans detect sounds 20-20k Hz)
• Problem Neurons can only fire 1000x/sec
• (Freq Th doesnt explain how hi pitch is det)
• gtgtgtgtVolley Principle-workgroups of neural cells
  synchronize alternate firing reloading
• (remember refractory period/ resting pause from
  Ch 2)

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• Hair cells activate neural impulses in neurons on
  Organ of Corti-

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Sound Localization (2004 AP Essay Q)
Sound travels at 750 miles per hour
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Hearing Loss

• Conduction Hearing Loss
• Inability to conduct vibrations due to eardrum
  puncture or damage to middle ear bones (digital
  hearing aids amp vib)
• Sensorineural/ Nerve Hearing Loss
• damage to the cochleas receptor cells or to the
  auditory nerve, aging, loud noise/music, disease
• Coch implant (translates sound into neural imp)
• Wont work in deaf adults whove spent a life w/o
  hearing? WHY NOT??????

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Deaf Culture

• Deaf Culture-Natl Assoc of Deaf deafness
  isnt a disability
• gtgtobjects to using cochlear implants in children
  who were deafened before learning to speak
• gtgtdeafness could be considered visual
  enhancement v hearing impairment
• Auditory Cortex in deaf is sensitive to touch and
  visual input
• Helen Keller visual aud cort sensitive to
  touch.
• FYI - Older adults have more trouble hearing high
  pitched sounds but are okay w/ low pitch Why?
• Degeneration near beginnning of basilar membrane
• Which th does this spt?
• Place Theory

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Aging Effects

• Det of high frequencies difficult in older people

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Other Senses

• 10.  Describe the sense of touch, and explain the
  basis of pain.
• 11.  Describe the senses of taste and smell, and
  comment on the nature of sensory interaction.
• 12.  Distinguish between kinesthesis and the
  vestibular sense.

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Touch

• 4 Separate Skin Senses
• pressure
• only skin sensation with identifiable receptors
• warmth
• cold
• Pain
• Relnshp b/w warmth, cold, pain and receptors that
  respond to them remains a mystery.

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Touch

• Other skin sensations are variations of the basic
  4
• Stroking adjacent pressure spots tickle
• Gentle stroking of pain spot itching sensation

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Pain

• pain is way of telling us that something is wrong
• gtgtpeople born w/o ability to feel pain die young
  (excess joint strain, infections from not
  shifting)
• pain is a sense, but the brain has a big effect
  on it as well
• ex. Phantom limb- 7 out of 10 amputees report
  pain or
• movement in their nonexistent limbs
• Ex. Placebo effect
• Fyi-no single stimulus that triggers pain no
  special receptors
• gtgtlow pain stimuli can produce other sensations
• warmth, coolness, smoothness, roughness

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Pain

• Gate-Control Theory (Ronald Melzack Patrick
  Wall)
• theory that the spinal cord contains a
  neurological gate that blocks pain signals or
  allows them to pass on to the brain
• gate opened by the activity of pain signals
  traveling up small nerve fibers
• gate closed by activity in larger fibers or by
  information coming from the brain (ie.
  endorphins)
• in theory you can treat pain by stimulating
  larger nerve fibers (massage, muscle stim,
  acupuncture)
• gtgtcause gate closing activity in large neural
  fibers
• gtgtLamaze method of Pain Control combines
  relaxation, counterstimulation distraction

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Pain

• Brains role in pain contd---
• Pain gate closed by endorphins
• eg. 1979-Ohio St B-Ball player finishing game w/
  broken neck
• Brain can also produce pain when no physical
  ailment is observed
• Brains Recording of Pain (exp memories of pain)
• Brain records peak moment of pain and how much is
  felt at end of experience
• Daniel Kahneman 1993
• gtgt2 trials trial 1 -put hand in cold H2O for
  60 sec
• trial 2 - put hand in cold H2O for 60 sec
  then immediately switch to slightly less cold
  for 30 sec
• Subjects said theyd rather rep T 2
• Implications for med procedures (ie. Colon exams)

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Pain

• More on Brains Role
• Roger Urlich 1994-
• Surgery patients assigned to rooms looking out on
  trees less pain med faster discharge than
  patients in identical rooms w/ a view of brick
  wall

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Taste
Did u know?-alc smk dec taste sens

• also called gustatory sense
• involves 4 basic sensations
• sweet, sour, salty, and bitter (more recently
  umami ltmeatygt)
• Taste Smell are a chemical senses (unlike vis
  aud)
• 200 taste buds on top sides of tongue, each w/
  a pore that catches food molecule that is sensed
  by 50-100 taste receptors w/in pore (10-20k
  taste recep)
• each type of sensation has its own specialized
  taste buds
• taste receptors reproduce themselves about every
  1 to 2 weeks
• age taste buds sensitivity tongue
  plasticity if 1 side damaged, other side
  becomes supersensitive
• If no tongue, can still taste taste
• buds on top back of mouth

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Taste
Did u know?-alc smk dec taste sens

• Sensory Interaction one sense influences another
• especially true with taste and smell
• gtgtpeople whove lost sense of smell think theyve
  lost taste
• gtgtcant taste when have a cold
• Best eg of S.I.
• gtgtSMELL TASTE TEXTURE FLAVOR

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Smell
Taste Smell chemical senses

• also called olfaction
• Molecules of substances reach 1 of 5 mil receptor
  cells in olfactory membrane
• olfactory nerve carries signals to the brain
  (olfactory cortex)
• (the one sense not routed through the thalamus
  at top of brainstem)
• gtgtstill a mystery how exactly olf rec cells work
• odors can evoke strong memories feelings.. WHY?
• Hotline b/w olf cortex ?limbic system (seat of
  emotion memory)
• Makes EVOL sense
• gtgtolf cortex evolved first mammalian ancestors
  smelled food and predators (rest of cortex
  development came later ie. Assoc areas)

Papillae-visible bumps on tongue that contain
taste buds
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Smell
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Age, Sex and Sense of Smell
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Body Position and Movement

• Kinesthesis- system for sensing the position and
  movement of individual body parts
• Receptors located in muscles, tendons, and joints
•   athletes-strong kinesthetic sense
• Vestibular Sense-the sense of body movement and
  position, including the sense of balance
• based in the inner ear (semi-circular canals,
  vestibular sacs)
•  head mvmt triggers fluid to stimulate hair-like
  receptors in these organs which sends msgs to
  cerebellum (rem balance voluntary mvmt)
• gtgtexp why if head is off balance, whole body is
  off
• gtgtafter spinning, neither fluid nor kinesth
  receptors immediately return to neutral ---- why
  you still feel like youre spinning
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