Unit 4 Sensation and Perception

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Unit 4-Sensation and Perception

• AP Psychology
• University High School
• 2007-08

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Sensation and Perception

• How do we create mental representations of the
  outside world?
• sensation the process by which our sensory
  receptors and nervous system create an awareness
  of the properties of an object or event in the
  environment
• perception the act of organizing and
  interpreting sensory input, enabling us to
  recognize meaningful objects and events
• Our sensations and perceptions can sometimes
  mismatch

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Simultaneous Contrast Illusion
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Muller-Lyer Illusion
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Guardians of the Secret
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Types of Processing

• bottom-up processing processing that is
  initiated by stimulus input begins with senses
  and works up to brains integration of sensory
  information
• top-down processing processing that is guided by
  knowledge, expectations, or beliefs

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Basic Principles of Sensation

• threshold the point at which sensory information
  is strong enough to be noticed
• absolute threshold the smallest amount of a
  sensory stimulus needed to notice that the
  stimulus is there at all
• just noticeable difference (JND) the size of a
  difference in a stimulus property needed to
  notice that a change has occurred
• Webers law size of a JND depends on the overall
  magnitude of the stimulus stimuli must differ by
  a constant minimum percentage, rather than a
  constant amount

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Subliminal Sensation

• Can we be influenced by sensory input that is
  subliminal?
• subliminal below threshold a signal that is
  not registered by our conscious awareness
• Lots of potential examples
• EAT POPCORN and DRINK COKE at NJ movie
  theater
• Disney movies
• Satanic/suicidal messages hidden in songs
• 2000 G.W. Bush campaign commercial RATS
• self-help tapes
• McDonalds ad on Iron Chef America

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So do subliminal messages work?

• In a sense, yes
• priming the tendency for frequently or recently
  used words or ideas to come to mind easily and
  influence the interpretation of new information
• Higgins et al. (1977)
• IV as part of a memory experiment,
  participants presented with list of
  positive/negative words (brave, independent,
  adventurous vs. reckless, foolish, careless)
• in second study, read story about man who
  climbs mountains, participates in demolition
  derbies, and tried crossing the Atlantic Ocean in
  a sailboat
• DV favorability of impressions of man in second
  study
• result participants primed with positive words
  created a more positive impression of the man

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Priming, cont.

• Bargh Chartrand, 1999
• IV participants completed word search puzzle
  that contained neutral/achievement-related words
  (table, floor, pencil vs. strive, win, compete)
• then left alone for 3 minutes to form as many
  words as possible from a set of Scrabble letters
• after 3 minutes, notified via intercom to stop
• DV percentage of participants who continued to
  write down words after being instructed to stop
  (hidden cameras)

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Bargh Chartrand (1999) results

• Priming can affect not only our perceptions (e.g.
  adventurous vs. reckless man), but also our
  social behaviors.

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Priming, cont.

• Bargh, Chen, Burrows (1996)
• participants given 30 sets of words in scrambled
  order (e.g. he it hides finds instantly),
  instructed to use some of those words to make
  grammatical sentences
• IV scrambled word sets contained
  politeness/rudeness/neutral words (respect,
  considerate, courteous vs. disturb, intrude,
  bluntly vs. chair, lamp, keys)
• instructed to find experimenter down the hall
  when task is complete experimenter in
  conversation for 10 minutes without acknowledging
  participant
• DV percentage of participants who interrupted
  conversation

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Bargh, Chen, Burrows (1996) results
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Subliminal Sensation

• So we know that primes can influence our thoughts
  and behaviors do subliminal advertisements work
  this way too?
• not much evidence for long-term effects of
  subliminal ads, self-help tapes, etc.
• Why the difference between priming studies and
  subliminal message studies?
• priming immediate, short-term effect on simple
  judgments and actions
• subliminal messages aim for long-term effects on
  consumer purchases, voter sentiment, or even
  suicide
• But then cant a subliminal message affect
  short-term consumer purchases, etc.?

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Strahan et al., 2002

• hypothesis people perceive subliminal cues
• only act on them when already motivated to do so
• IVs thirsty/not thirsty participants
  subliminally exposed to thirst-related/neutral
  words (e.g. thirst, dry vs. pirate, won)
• DV amount of Kool Aid consumed in second taste
  test (ml)

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Strahan et al. (2002) results
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Subliminal Sensation The Bottom Line

• Subliminal messages may have the potential to
  affect our short-term decisions, behaviors, etc.
• may depend on motivation (striking while the
  iron is hot)
• Subliminal messages not very likely to have
  long-lasting effects on our attitudes, behaviors,
  etc.

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Basic Principles of Sensation

• signal detection theory a theory explaining why
  people detect signals, which are always embedded
  in noise, in some situations but not others

Reported signal?
Yes
No
Yes
Signal?
No
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Signal Detection Theory, cont.

• People are quicker to detect a signal among noise
  when
• they expect the signal
• it is important that the signal is detected
• they are alert
• Experience matters in detecting signals
• 10 hours of playing an action video game
  increased novice players signal detection skills
  (Green Bavelier, 2003)

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Basic Principles of Sensation

• sensory adaptation diminished sensitivity as a
  consequence of constant stimulation
• allows us to focus on informative changes in our
  environment
• transduction transforming sensory input (light
  waves, sound waves, etc.) into neural impulses
  our brain can interpret

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Vision

• eyes register light waves reflected from, or
  produced by, objects in the line of sight

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Properties of Light

• amplitude the height of the peaks in a light
  wave
• determines brightness (larger amplitude
  brighter colors)
• frequency the rate at which light waves move
  past a given point
• higher frequency shorter wavelength
• determines hue (short wavelength blue, long
  red)

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The Eye (pg. 132 in your text)
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The Eye

• cornea transparent covering protects the eye,
  bends light to provide focus
• light enters the eye through the pupil, a small
  adjustable opening
• size of the pupil adjusted by iris, a circular
  colored muscle

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The Eye

• lens transparent structure behind the pupil that
  changes shape to focus an image on the back of
  the eye
• ciliary muscle controls curvature of lens to
  achieve focus (accomodation)
• retina light-sensitive inner surface of the eye

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Inversion of Images

• image projected upside down on retina, once it
  passes through lens
• receptor cells in retina convert light into
  neural impulses, which are organized by brain
  into meaningful structures
• vision is constructed by brain, rather than
  merely received

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Nearsightedness Farsightedness
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The Retina

• receptors in the retina called rods and cones
• rods retinal cells that detect black, white, and
  gray necessary for peripheral and twilight
  vision
• cones retinal cells that detect colors and fine
  detail function in daylight and well-lit
  conditions
• fovea central part of the retina with the
  highest density of cones and the highest
  resolution (contains virtually no rods)

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The Retina

• rods and cones connected to ganglion cells
• ganglion cells axons create the optic nerve (a
  bundle of nerve fibers that carry messages from
  the retina to the thalamus)
• no rods or cones at spot where optic nerve leaves
  eye (blind spot)

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Visual Information Processing

• How do our eyes/brain transform light waves into
  an image in our mind?
• retinal receptor cells extremely sensitive and
  specialized
• feature detector neurons nerve cells in the
  visual cortex that respond to very specific
  features of a stimulus, such as shape, angle, or
  movement (Hubel Weisel, 1979)

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Visual Information Processing

• individual feature detectors pass their
  information to areas of cortex that interpret the
  patterns of information
• fMRI reveals specific areas of cortex for
  specific categories of objects (e.g. region of
  temporal lobe for face recognition, different
  region for chairs)
• We can tell if a person is looking at a shoe, a
  chair, or a face, based on the pattern of their
  brain activity. (Haxby, 2001)

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Visual Information Processing

• serial vs. parallel processing
• serial processing processing of information
  step-by-step in a specific order (e.g. computers,
  conscious problem solving)
• parallel processing processing several aspects
  of information simultaneously (e.g. vision, many
  other brain activities)
• brain simultaneously perceives color, depth,
  movement, and form (Livingstone Hubel, 1988)
• integrates information on-the-fly and allows
  for almost instantaneous recognition of objects

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Color Vision

• Objects do not possess color (in a sense, the
  tomato isnt red, its everything but red...)
• long wavelengths of red light are rejected
  (reflected) from the tomato
• The light rays are not coloured. (Isaac
  Newton, 1704)
• Color is a product of our brains transduction of
  light waves.
• JND so low that we can discriminate between over
  7 million colors (Geldard, 1972)

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Color Vision

• 19th century debate about how we see color
• one camp followed work of Thomas Young and
  Hermann von Helmholz on primary colors
• 3 primary colors red, yellow, and blue
• any color can be created using a combination of
  the primary colors
• trichromatic theory of color vision color vision
  arises from the combinations of neural impulses
  from three different kinds of sensors, each of
  which responds maximally to a different
  wavelength (red, green, and blue)
• combinations of stimulation of these three types
  of cones leads to our vast experience of colors

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Color Vision

• other camp took lead from Edward Hering
• some colors cannot be mixed (e.g. no such thing
  as reddish-green or yellowish-blue)
• opponent process theory of color vision the
  presence of one color of a pair inhibits
  perception of the other color in the pair
  (opponent cells)
• red-green, yellow-blue, black-white
• evidence for opponent-process theory from the
  phenomenon of afterimages

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Afterimages
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Afterimages

• afterimage the image left behind by a previous
  perception
• one member of a pair of opponent cells inhibits
  the other (e.g. seeing green inhibits red)
• green stimulus disappears, freeing up red
  receptors
• red receptors, previously inhibited, temporarily
  overshoot the mark

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Color Blindness

• an inability, either acquired (by brain damage),
  or inherited, to perceive hue
• more common among men than women
• most color-blindness inability to distinguish
  between red and green

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Visual Perception

• first of step of visual perception is to organize
  sensory input into shapes that correspond to
  objects, and to specify their sizes and locations
• figure the set of characteristics that
  correspond to an object (shape, color, texture,
  etc.)
• ground the background, which must be
  distinguished in order to pick out figures

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Visual Perception

• figure-ground relationship can be ambiguous
• but even then, either the faces or the vase is
  the figure, and the other acts as the ground

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Visual Perception

• What do you see in this picture?
• In cases of ambiguity, the mind actively
  organizes the visual world.

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Depth Perception

• the ability to see objects in three dimensions,
  even though the images that strike the retina are
  in two dimensions
• allow us to judge distance
• depth perception is at least partly innate
• visual cliff studies (Gibson Walk, 1960)

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Visual Cliff
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Depth Perception

• other newborn animals besides humans respond
  similarly to visual cliff
• young kittens, day-old goat, newly hatched
  chicks, etc.
• ability to perceive depth is due to two types of
  cues
• binocular cues
• monocular cues

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Binocular Cues to Depth

• cues to depth perception that arise from the use
  of both eyes working together
• 2 eyes have slightly different views of the world
  because they are in slightly different places
• need to cross eyes slightly to focus object on
  fovea of both eyes
• doing so leads other objects to appear on
  different spots in the 2 retinas (retinal
  disparity the difference between the images
  striking the retinas)
• more disparity closer object less disparity
  further object

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Floating Finger Sausage
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Monocular Cues to Depth

• cues to depth perception that can be perceived by
  one eye alone
• relative size the larger an object appears, the
  closer we think it is

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Monocular Cues to Depth

• interposition objects that block the view of
  another are perceived as being closer

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Monocular Cues to Depth

• relative clarity hazy objects are perceived as
  being further away than clear objects (light
  scatters in the atmosphere)

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Monocular Cues to Depth

• texture gradient progressive changes in the
  texture of an object
• objects far away seem smaller and more closely
  packed

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Monocular Cues to Depth

• relative height objects higher in field of
  vision appear farther away
• lower part of figure-ground image typically seen
  as figure, upper seen as ground (Vecera et al.,
  2002)

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Monocular Cues to Depth

• relative height objects higher in field of
  vision appear farther away
• lower part of figure-ground image typically seen
  as figure, upper seen as ground (Vecera et al.,
  2002)

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Monocular Cues to Depth

• relative motion (motion parallax) as we move,
  stationary objects sometimes seem to move too
• objects closer than fixation point seem to move
  backwards (closer to you faster movement)
• objects further than fixation point seem to move
  forwards (further from you faster movement)

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Monocular Cues to Depth

• linear perspective parallel lines appear to
  converge with distance

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The Ames Room
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The Ames Room Revealed
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Monocular Cues to Depth

• light and shadow nearby objects reflect more
  light to our eyes (dimmer objects seem further
  away)

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Motion Perception

• We see movement that is actually there...
• spot on inferior portion of occipital lobe
  responsible for tracking movement (Mrs. M)
• ...but our mind also creates movement.
• movies are actually a rapidly-presented slideshow
  (24 frames per second)
• phi phenomenon an illusion of movement created
  when two or more lights blink on and off in quick
  succession

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Perceptual Constancy

• So far weve discussed how we see color, shapes,
  depth, movement, etc.
• senses tuned to detect change
• Why dont we get confused when we see an object
  from a different angle, under different light,
  from a different distance?
• perceptual constancy the perception of
  characteristics of objects as the same even
  though the sensory information striking the eyes
  changes
• relies on top-down processing, drawing from
  experience and understanding of the world

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Perceptual Constancy

• size constancy seeing an object as being the
  same size when viewed at different distances

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Perceptual Constancy

• shape constancy seeing objects as having the
  same shape even when the image on the retina
  changes

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Perceptual Constancy

• size-distance relationship interacts with
  perceptual constancy
• brain effortlessly calculates size of objects
  based on distance

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Mueller-Lyer Illusion
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Past Experiences and Perceptual Interpretation

• cataract cloudiness in the eyes lens that
  allows the eye to only see diffused, foggy
  light
• cataracts in childhood can lead to different
  methods of face recognition (LeGrand et al.,
  2004)
• normal eyes recognize face as a complete whole,
  instantly
• cataracts in infancy recognize faces as a
  collection of individual recognizable features
  no instant face recognition
• cataracts from infancy also lead to perceptual
  constancy deficits (Bower, 2003)
• critical period in infancy for sensory and
  perceptual development
• cataracts developed later in life do not affect
  perceptions

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The Thatcher Illusion
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Past Experiences and Perceptual Interpretation

• This tendency to have a mental predisposition to
  perceive one thing and not another is known as a
  perceptual set.
• perceptual set determined by our schemas
• schema concept or framework that organizes and
  interprets information

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Past Experiences and Perceptual Interpretation

• Our past experiences guide our perceptions, but
  we can also adjust to radically new perceptions
  with time (perceptual adaptation).
• George Stratton (1896) invented glasses that
  flipped left to right, and up to down wore them
  for 8 days
• walking, eating nearly impossible at first
  became sick and depressed
• by day 8, could walk without running into things,
  could reach in the right direction
• readapted quickly after taking off headgear

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Past Experiences and Perceptual Interpretation

• deficits to one sense can result in increased
  sensitivity of other senses (plasticity).
• blind musicians more likely than sighted ones to
  develop perfect pitch (Hamilton, 2000)
• with one ear plugged, blind people more accurate
  than sighted people at locating a sound source
  (Gougoux et al., 2005 Lessard et al., 1998)

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Hearing

• If a tree falls in the woods but nobody hears it,
  is there a sound?
• sound waves created by a vibrating object
• any type of molecules (gas, liquid, solid) that
  can move and create a pressure wave can produce
  sound
• waves received by ears, transduced into neural
  signals
• Without ears, the waves are just waves, not
  sound. The falling tree makes no sound.

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Sound Waves

• amplitude corresponds to volume
• larger amplitude louder sound
• smaller amplitude softer sound
• wavelength corresponds to pitch
• longer wavelength lower pitch
• shorter wavelength higher pitch

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Sound Waves

• sound intensity measured in decibels
• logarithmic measure of the volume of different
  stimuli as compared to a reference point
  (threshold)
• prolonged exposure above 85 decibels can cause
  hearing damage

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Structure of the Ear (pg. 139)
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Structure of the Ear

• sound waves enter the ear and strike the eardrum
  (tympanic membrane)
• ear drum vibrations move the three tiny bones in
  the ear (hammer, anvil, stirrup)
• bones amplify sound and transmit it to the
  basilar membrane, which is inside the cochlea

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Structure of the Ear

• basilar membrane lined with tiny projections
  called hair cells
• hair cells hearing rods and cones vision
• vibration in bones causes basilar membrane to
  vibrate
• vibration in basilar membrane causes hair cells
  to fire, triggering neural impulses to brain

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Auditory Transduction

• Two explanations of how basilar membrane converts
  pressure waves to perceived sound (i.e. how we
  perceive pitch)
• 1. place theory different frequencies activate
  different parts of the basilar membrane
• 2. frequency theory higher frequencies greater
  neural firing
• But neurons can fire, at most, 1000 times per
  second. How do we hear sounds that are at a much
  greater frequency? (e.g. the upper third of a
  pianos keyboard)
• volley principle
• primary auditory cortex in temporal lobe
• different pitches registered by different neurons
  within auditory cortex (like feature detectors in
  vision)

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Locating Sounds

• two ears work together to locate the source of a
  sound
• 1. difference in phase sound waves reach ears at
  slightly different points in wave cycle
• 2. difference in loudness ear closer to sound
  source registers louder signal
• 3. difference in onset ear closer to sound
  source registers signal slightly sooner
• tiny differences, but enough for us to perceive
• e.g. difference in onset of 0.000027 seconds can
  be distinguished

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Hearing Without Awareness

• cocktail party phenomenon the effect of not
  being aware of the content of other peoples
  conversations until your name is mentioned, then
  suddenly hearing it
• processing signal bottom-up, but top-down
  awareness isnt drawn until self-relevant
  information is introduced
• dichotic listening task different stimuli
  delivered to two ears via headphones instructed
  to monitor only one signal
• still perceive some information (e.g. speakers
  gender) from ignored ear (Treisman, 1964)

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Music

• important part of virtually all cultures,
  sometimes to the point of even being regulated by
  law
• former Soviet Union certain chords were outlawed
  for being too decadent
• North Carolina singing out of tune was at one
  time a prosecutable offense
• Music works because of distances between notes
  (Krumhansl, 2000)
• temporal distance (e.g. slow vs. fast tempo)
• tonal distance (e.g. low vs. high pitch)

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Deafness

• more than 28 million Americans have hearing
  difficulty
• like color blindness, can be inherited or
  acquired
• more than 30 genes have been linked to deafness
  (Lynch et al., 1997)

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Deafness

• different types of deafness
• nerve deafness occurs when the hair cells are
  destroyed by loud sounds
• tinnitus constant ringing or noise in the ears
• symptom of deafness resulting from many possible
  causes (loud noises/nerve deafness, ear
  infections, even aspirin!)
• conduction deafness type of deafness caused by
  physical impairment of the outer or middle ear
• e.g. broken eardrum

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The Chemical Senses Taste Smell

• rely on sensing the presence of certain chemicals
• smell (olfaction)
• 10,000 smells detectable by humans
• large variation in sensitivity to smells
• some people are 20x more sensitive to smell than
  others (Rabin Cain, 1986)
• most people think they are good at detecting
  smells, but are surprisingly poor at it (de Wijk
  et al., 1995)
• Cain (1979) correctly identify only about half
  of 80 common smells
• women better than men at this (Cain, 1982)
• young adults better than children (up to 14) or
  middle-aged adults (40-50) at detecting smells
  (Cain Gent, 1991 de Wijk Cain, 1994 Murphy,
  1986)

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Smell

• molecules of certain substance sensed by about 5
  million receptor fibers on the roof of each nasal
  cavity
• different receptors for different smells, but not
  10,000 of them (about 1000)
• Like colors, we detect smell by the combination
  of receptors that fire.

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Smell and Memory

• Herz et al., 2004
• participants placed in a scented room, played a
  computer game that was rigged so they would
  always lose (frustration)
• IV complete subsequent verbal task while exposed
  to same smell/different smell/no smell
• DV amount of time spent on verbal task
• results same smell group gave up task
  significantly earlier than other two groups
• Smells can also evoke pleasant memories
  (Ehrlichman Halpern, 1988)

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Smell and Memory

• Why are smell and memory so closely linked?
• evolutionary explanation smell used by most
  mammals to detect food (good or bad) and poison
• basic, but critical, role led to early
  development of smell-memory relationship
• biological explanation two major neural tracks
  that deliver olfactory information
• one through thalamus to hippocampus (memory)
• other through limbic system (emotion)

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Smell and Pheromones

• pheromones chemical substances produced by the
  body that serve as a means of interpersonal
  communication
• McClintock (1971) female roommates tend to
  synchronize menstrual cycles
• effect depends on pheromones reaching the nose
  (Stern McClintock, 1998 Russell et al., 1980)
• pheromones associated with sexual attraction
  (e.g. Berglund et al., 2006)
• PET scans show that heterosexual and homosexual
  males brains respond differently to pheromones
  (homosexual male activation similar to that of
  heterosexual women)
• homosexual female activation similar to that of
  heterosexual men

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Taste

• taste buds microscopic structures on the bumps
  on the tongue surface, at the back of the throat,
  and inside the cheeks
• taste buds die and are replaced every 10 days
  (McLaughlin Margolskee, 1994)
• number of taste buds, and sensitivity, decrease
  with age (Cowart, 1981)

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Taste

• tastes of all foods are a combination of four
  basic tastes bitter, sour, salty, and sweet
• free nerve endings in mouth irritated by spicy
  foods? (Lawless, 1984)
• Taste and smell closely related senses
• aspartame (NutraSweet) tastes sweeter when
  smelling vanilla (Sakai et al., 2001)
• both types of information converge on same region
  of frontal lobe critical for perception of flavor
  (Schul et al., 1996)

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Somasthetic Senses

• senses that have to do with perceiving the body
  and its position in space
• specifically touch, kinesthetic sense, vestibular
  sense, pain sense, and (possibly) magnetic sense
  and ESP
• touch
• skin largest organ
• millions of sensory receptors combinations of
  receptor activation lead to different types of
  touch
• sensory cortex divided by body part more cortex
  more sensitivity (Weinstein, 1968)
• brain tuned to be more sensitive to unexpected
  stimulation
• women more sensitive to touch than men
  (Weinstein, 1968)

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Somasthetic Senses

• kinesthetic sense the sense that registers the
  movement and position of the limbs
• two types of specialized cells important to
  kinesthetic sense (Pinel, 1993)
• 1. in tendons (connect muscles to bones)
  triggered by tension
• 2. in muscles themselves triggered by length of
  muscle

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Somasthetic Senses

• vestibular sense the sense that provides
  information about the bodys orientation relative
  to gravity
• relies on semicircular canals in the inner ear
• filled with fluid and cilia (tiny hairs) detect
  balance by sensing fluids movement

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Pain

• Despite how it feels, pain is a good thing for
  us.
• alerts us to something wrong, signals us to
  change behavior
• people born without ability to feel pain usually
  die by early adulthood

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What is pain?

• Pain is a product of both bottom-up and top-down
  processing.
• bottom-up damage to a portion of the body sends
  signals to the sensory cortex (parietal lobe),
  indicating a problem
• top-down brain anticipates pain, body feels
  expected pain
• Armel Ramachandran (2003) slightly bent unseen
  fingers of participants while simultaneously
  severely bending finger on fake rubber hand
• participants felt severe twist reported more
  pain, increased perspiration

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Gate-Control Theory of Pain

• theory that the spinal cord contains a
  neurological gate that either blocks pain
  signals or allows them to continue to the brain
  (Melzack Wall, 1965)
• 2 types of nerve fibers in spinal cord short and
  long
• short nerve fibers conduct pain signals, open
  the gate
• long nerve fibers conduct most other sensory
  information, close the gate
• one way to treat pain may be to activate long
  nerve fibers via massage, electric stimulation,
  or acupuncture (Wall, 2000)
• e.g. rubbing the injured area

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Controlling Pain

• pain at the intersection of mind and body
• can be controlled by physical or psychological
  interventions?
• e.g. morphine painkiller, operates on physical
  level (bottom-up)
• but, placebos activate some of the same brain
  structures as painkillers (and work to alleviate
  pain!) (Petrovic et al., 2002 Wager et al.,
  2004)
• Lamaze classes relaxation (deep breathing,
  muscle relaxation), counterstimulation (gentle
  massage), and distraction (focusing on something
  else)
• Surgery patients whose rooms face trees require
  less pain medication and recover more quickly
  than those whose rooms face brick walls. (Ulrich,
  1984)

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Magnetic Sense

• Birds migrate using magnetic field of the Earth
• tiny bits of iron in bird neurons involved in
  migration? (Gould, 1988 Kirschvink et al., 2001)
• some evidence of weak magnetic sense in humans?
• magnetite deposit in bones of nose
• Poorly understood sense, hard to say yet whether
  humans actually possess it or not...

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Extrasensory Perception (ESP)

• the claim that perception can occur without
  sensory input
• telepathy the ability to send and receive
  thoughts directly, mind to mind
• clairvoyance the ability to know about distant
  events, without sensory information
• precognition the ability to predict future
  events
• psychokinesis? the ability to move objects
  mentally, without physically manipulating them
• not actually part of ESP claims doesnt involve
  perception or knowing

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Extrasensory Perception (ESP)

• There have been some well-publicized cases of
  alleged ESP
• e.g. Nostradamus
• In the City of God there will be a great
  thunder, two brothers torn apart by Chaos, while
  the fortress endures, the great leader will
  succumb. The third big war will begin when the
  big city is burning. (1654)

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Extrasensory Perception (ESP)

• How do we test ESP empirically?
• senders telepathically transmit 1 of 4 visual
  images to a receiver in a nearby room (e.g. Bem
  Honorton, 1994)
• 32 accuracy rate! (better than 25 expected by
  chance)
• Are these results reliable?
• No... consistent failure to replicate ESP
  findings
• not known how brain would send or receive ESP
  signals
• What form would these signals take? (waves?
  chemicals? something else?)

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Synesthesia

• comes from the Greek syn (union) aisthises
  (of the senses)
• phenomenon in which stimulation of one sensory
  pathway leads to automatic experiences in a
  second sensory pathway
• up to 1 in 23 people experience synesthesia
  (Simner et al., 2006)

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Synesthesia

• lots of forms almost any two senses can be
  linked via synesthesia
• some common types
• grapheme ? color synesthesia
• letters and/or numbers associated with specific
  colors
• associations vary from person to person, but
  there are some common pairings (e.g. A and red, O
  and white/black, S and yellow) (Day, 2005)
• music ? color synesthesia
• specific tones or songs associated with specific
  colors
• again lots of variation, but still some common
  trends (e.g. higher pitches brighter colors)
  (Ward et al., 2006)
• lexical ? gustatory synesthesia
• individual words and sounds associated with
  experience of specific tastes (e.g. /k/ paired
  with taste of eggs)
• very rare form of synesthesia, not yet well
  understood

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Synesthesia

• Why does synesthesia happen?
• increased communication between specialized parts
  of the brain that are physically close to one
  another?
• e.g. letter/number recognition (green) and color
  processing (red)

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Synesthesia

• How do we know that synesthesia is real?
  Couldnt synesthetes just be faking it?
• test-retest reliability giving the same test of
  synesthesia multiple times over a long period of
  time
• synesthetes 90 reliability
• non-synesthetes 30-40 reliability, even when
  warned that retesting will occur (Baron-Cohen et
  al., 1996)

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Attention The Gateway to Awareness

• attention the act of focusing on particular
  information, which allows it to be processed more
  fully than information not attended to
• selective attention the process of picking out a
  particular quality, object, or event for
  relatively detailed analysis
• We attend to things either when they somehow grab
  our attention, or when we purposely search for
  them.

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Attention The Gateway to Awareness

• What grabs our attention?
• pop-out occurs when a stimulus is sufficiently
  different from the ones around it that it is
  immediately evident
• occurs when objects differ in fundamental
  qualities, such as size (vision) or frequency
  (hearing)

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Pop-out
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Pop-out
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Attention The Gateway to Awareness

• Sometimes we are actively searching for specific
  objects...

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Attention The Gateway to Awareness

• biological differences in grabbing attention vs.
  voluntary attention
• sudden changes in the environment that grab our
  attention activate the superior colliculus
  (brainstem structure underneath the thalamus)
  automatic reflexive redirection of attention
• area in temporal lobe active during bottom-up
  processing (Corbetta Schulman, 2002)
• None of these areas are active during voluntary
  attention when you are searching for something.
• instead, area of frontal lobes and parietal lobes
  active (Corbetta Schulman, 2002 Hoph Mangun,
  2000 Snyder et al., 2000)

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Attention The Gateway to Awareness

• change blindness failure to detect large changes
  in a visual scene
• Simons Levin (1998)

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Attention The Gateway to Awareness

• One other limit to attention we cannot simply
  turn off our bottom-up processes in service of
  our top-down attention
• e.g. Stroop effect
• name the color of the ink used for each of the
  following words

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BLUE
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GREEN
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RED
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ORANGE
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RED
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BLUE
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GREEN
121
ORANGE
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Sensation and Perception Summary

• Sensory information is detected by the various
  senses (sensation), and interpreted and organized
  by the brain (perception).
• Our perception of the world is not merely a
  product of sensory input. The eyes are not just
  cameras, the ears are not just tape recorders.
• We create our experience using our beliefs,
  expectations, etc.