Sensation and Perception

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Sensation and Perception

• Sensation your window to the world
• Perception interpreting what comes in your
  window.
• Bottom Up and Top Down Processing!

2
Sensory Adaptation

• Decreased responsiveness to stimuli due to
  constant stimulation.
• Not hearing the fan in the room.
• Smell of perfume diminishes
• Walk into a restaurant

Do you feel your underwear all day?
3
Cocktail-party phenomenon

• The cocktail party effect describes the ability
  to focus one's listening attention on a single
  talker among a mixture of conversations and
  background noises, ignoring other conversations.
• Form of selective attention.

4
Transduction

• Transforming signals into neural impulses.
• senses ?thalamus , ? other brain parts.

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Sensation- Thresholds

• Absolute Threshold
• minimum stimulation needed to detect a particular
  stimulus
• defined as the stimulus needed for detection 50
  of the time
• Difference Threshold or just noticeable
  difference (JND)
• minimum difference between two stimuli that a
  subject can detect 50 of the time
• increases with magnitude, need more difference
  with more weight (Webers Law)
• Signal Detection Theory
• No single absolute due to outside factors
• Sentry during war, new mommy, average homebody

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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

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Sensation- Thresholds

• Signal Detection Theory
• Assumes TWO things going on
• 1. sensitivity to stimulus (physical)
• 2. response bias also called decision criterion
  (psychological)
• Can measure plot these in a Receiver Operating
  Characteristic curve (ROC curve)

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Sensation- Thresholds

• Webers Law- to perceive a difference between
  two stimuli, they must differ by a constant
  proportion
• a constant for each sense
• light intensity- 8, weight- 2
• tone frequency- 0.3
• Just noticable difference has a proportion to be
  met in order to sense difference

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Webers Law

• Classic and still identified today but it did not
  account for extreme values.175 watt and a 200
  watt
• Ability to recognize difference diminishes.so in
  1860s

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Sensation- Thresholds

• Fechners Law- upgrade of Webers law
• includes increase of jnd with extreme
  measures/magnitude
• Adding the relationship of the perceived
  magnitude to physical intensity of a stimuli
• Same basic idea
• ½ pound book in 2lb vs. 60lb backpack
• 1 voice in chorus of 10 versus 2 in 20

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Sensation- Thresholds

• Stevens Power Law - upgrade to Fechner
  (Fechners law didnt work for pain, other
  stimuli)
• Strength of a sensation related to the intensity
  of the stimuli raised to some power
• So pain like electric shock you will sense a a
  small change at higher intensities than at the
  lower intensities when more may be needed to
  recognize difference

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Stevens
Fechner
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Vision

• Our most dominating sense.
• Visual Capture
• What we see surpasses what we feel, taste, smell,
  or hear.most seen in experiments with hearing

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Phase One Gathering Light

• The height of a wave gives us its intensity
  (brightness).
• The length of the wave gives us its hue (color).
• ROY G BIV color schemas
• The longer the wave the more red.
• The shorter the wavelength the more violet.

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Phase Two Getting the light in the eye
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Phase Three Transduction
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Transduction Continued

• Order is Rods/Cones to Bipolar to Ganglion to
  Optic Nerve.
• Sends info to thalamus- area called lateral
  geniculate nucleus (LGN).
• Then sent to cerebral cortexes.
• Where the optic nerves cross is called the optic
  chiasm.

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Pathways from the Eyes to the Visual Cortex
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Phase Four In the Brain

• Goes to the Visual Cortex located in the
  Occipital Lobe of the Cerebral Cortex.
• Feature Detectors.
• Parallel Processing

We have specific cells that see the lines,
motion, curves and other features of this turkey.
These cells are called feature detectors.
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Retinas Reaction to Light

• Receptive fields regions in which receptors
  respond to light
• Lateral inhibition receptor (or neuron) making
  its neighbors less sensitive
• Helps in things like edge detection

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Visual Information Processing

• Feature Detectors
• neurons in the visual cortex respond to specific
  features
• shape
• angle
• movement

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Visual Information Processing

• Parallel Processing
• simultaneous processing of several dimensions
  through multiple pathways
• color
• motion
• form
• depth

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Visual Information Processing
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Visual Information Processing

• Neural pathways (multiple!)
• Optic nerve through optic chiasm (crossover),
  becomes the optic tract then
• Primary visual cortex (striate cortex) then
  splits into
• The what path (thru temporal lobes)
• The where path (up into parietal lobes)

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Color Vision
Two Major Theories
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Trichromatic Theory YoungHelmholtz theory

• Three types of cones
• Red
• Blue
• Green
• These three types of cones can make millions of
  combinations of colors.

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Visual Information Processing Color vision

• But Tri-chromatic didnt explain afterimages or
  color-blindness! So
• Opponent Process Theory
• Black-white receptors (for brightness
  saturation)
• Red-green receptors (for hue)
• Blue-yellow receptors (for hue)

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Opponent Process- Afterimage Effect
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Color-Deficient Vision

• People who suffer red-green blindness have
  trouble perceiving the number within the design

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Opponent-Process theory

• The sensory receptors come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is stimulated, the other is
  inhibited.

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Visual Information Processing

• Opponent-Process Theory- opposing retinal
  processes enable color vision
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black

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Afterimages
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Visual Information Processing Color vision

• So whos right???
• Turns out theyre both right
• Tri-chromatic theory works in the retina
• Opponent process works in the higher visual
  processing parts of the brain
• Together they explain what we know about color
  vision quite well.

34
Hearing
Our auditory sense
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We hear sound WAVES

• The height of the wave gives us the amplitude of
  the sound.
• The frequency of the wave gives us the pitch if
  the sound.

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The Ear
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Transduction in the ear

• Sound waves hit the eardrum then anvil then
  hammer then stirrup then oval window.
• Everything is just vibrating.
• Then the cochlea vibrates.
• The cochlea is lined with mucus called basilar
  membrane.
• In basilar membrane there are hair cells.
• When hair cells vibrate they turn vibrations into
  neural impulses which are called organ of Corti.
• Sent then to thalamus up auditory nerve.

It is all about the vibrations!!!
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Pitch Theories
Place Theory and Frequency Theory
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Place Theory

• Different hairs vibrate in the cochlea when they
  different pitches.
• So some hairs vibrate when they hear high and
  other vibrate when they hear low pitches.

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Frequency Theory

• All the hairs vibrate but at different speeds.

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Deafness

• Nerve (sensorineural) Deafness

• Conduction Deafness

• The hair cells in the cochlea get damaged.
• Loud noises can cause this type of deafness.
• NO WAY to replace the hairs.
• Cochlea implant is possible.

• Something goes wrong with the sound and the
  vibration on the way to the cochlea.
• You can replace the bones or get a hearing aid to
  help.

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Touch

• Receptors located in our skin.
• Gate Control Theory of Pain

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Taste

• We have bumps on our tongue called papillae.
• Taste buds are located on the papillae (they are
  actually all over the mouth).
• Sweet, salty, sour and bitter.

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Vestibular Sense

• Tells us where our body is oriented in space.
• Our sense of balance.
• Located in our semicircular canals in our ears.

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Kinesthetic Sense

• Tells us where our body parts are.
• Receptors located in our muscles and joints.

Without the kinesthetic sense you could touch the
button to make copies of your buttocks.