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					Chapters 5/6
Sensation and Perception
AP Psychology
Mr. Jaccarino
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…
Simultaneous Contrast Illusion
Muller-Lyer Illusion
Guardians of the Secret
Types of Processing
   bottom-up processing: processing that is initiated
    by stimulus input; begins with senses and works up
    to brain’s integration of sensory information
   top-down processing: processing that is guided by
    knowledge, expectations, or beliefs
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
            Weber’s 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
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
            Disney movies
            Satanic/suicidal messages hidden in songs
            2000 G.W. Bush campaign commercial: “RATS”
            self-help tapes
            McDonald’s ad on Iron Chef America
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,
                  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
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
        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)
Bargh & Chartrand (1999) results
    % of
participants 60                        Neutral
    who                                Achievement

   Priming can affect not only our perceptions
    (e.g. adventurous vs. reckless man), but
    also our social behaviors.
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
Bargh, Chen, & Burrows (1996) results
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 can’t a subliminal message affect
    short-term consumer purchases, etc.?
Strahan et al., 2002
   hypothesis: people perceive subliminal
     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)
Strahan et al. (2002) results
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.
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       Hit            Miss
                False          Correct
        No      alarm         rejection
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
     10  hours of playing an action video game
      increased novice players’ signal detection
      skills (Green & Bavelier, 2003)
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
   eyes register light waves reflected from, or
    produced by, objects in the line of sight
Properties of Light
   amplitude: the height
    of the peaks in a light
      determines
        brightness (larger
        amplitude = brighter
   frequency: the rate at
    which light waves
    move past a given
      higher frequency =
        shorter wavelength
      determines hue
        (short wavelength =
        blue, long = red)
The Eye (pg. 201 in your text)
The Eye
 cornea: transparent
  covering; protects
  the eye, bends light
  to provide focus
 light enters the eye
  through the pupil, a
  small adjustable
       size of the pupil
        adjusted by iris, a
        circular colored
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
   retina: light-sensitive
    inner surface of the
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
Nearsightedness & Farsightedness
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)
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)
Visual Information Processing
   How do our eyes/brain transform light
    waves into an image in our mind?
     retinalreceptor 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)
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,
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,
       integrates information “on-the-fly” and allows for
        almost instantaneous recognition of objects
Color Vision
   Objects do not “possess” color (in a sense,
    the tomato isn’t red, it’s everything but
       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)
Color Vision
 19th century: debate about how we see
 one camp: followed work of Thomas Young
  and Hermann von Helmholz on primary
       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
Color Vision
   other camp: took lead from Edward
     some  colors cannot be mixed (e.g. no
      such thing as “reddish-green” or
     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
   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
     red receptors, previously inhibited,
      temporarily overshoot the mark
Color Blindness
   an inability, either
    acquired (by brain
    damage), or
    inherited, to
    perceive hue
       more common
        among men than
   most color-
    blindness: inability
    to distinguish
    between red and
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,
       ground: the background,
        which must be
        distinguished in order to
        pick out figures
Visual Perception
   figure-ground
    relationship can be
       but even then,
        either the faces or
        the vase is the
        figure, and the other
        acts as the ground
Visual Perception
 What do you see in
  this picture?
 In cases of
  ambiguity, the mind
  actively organizes
  the visual world.
Depth Perception
   the ability to see objects in three
    dimensions, even though the images
    that strike the retina are in two
     allow   us to judge distance
   depth perception is at least partly
     visual   cliff studies (Gibson & Walk, 1960)
Visual Cliff
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
     monocular cues
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
       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
            more disparity = closer object; less disparity = further
Floating Finger Sausage
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
Monocular Cues to Depth
   interposition:
    objects that block
    the view of another
    are perceived as
    being closer
Monocular Cues to Depth
   relative clarity: hazy
    objects are
    perceived as being
    further away than
    clear objects (light
    scatters in the
Monocular Cues to Depth
   texture gradient:
    changes in the
    texture of an object
       objects far away
        seem smaller and
        more closely
Monocular Cues to Depth
   relative height:
    objects higher in
    field of vision
    appear farther
       lower part of figure-
        ground image
        typically seen as
        figure, upper seen
        as ground (Vecera
        et al., 2002)
Monocular Cues to Depth
   relative height:
    objects higher in
    field of vision
    appear farther
       lower part of figure-
        ground image
        typically seen as
        figure, upper seen
        as ground (Vecera
        et al., 2002)
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
       objects further than
        fixation point seem to
        move forwards (further
        from you = faster
Monocular Cues to Depth
   linear perspective:
    parallel lines
    appear to converge
    with distance
The Ames Room
The Ames Room Revealed
Monocular Cues to Depth
   light and shadow:
    nearby objects
    reflect more light to
    our eyes (dimmer
    objects seem
    further away)
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
Perceptual Constancy
   So far we’ve discussed how we see color,
    shapes, depth, movement, etc.
       senses tuned to detect change
       Why don’t 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
Perceptual Constancy
   size constancy:
    seeing an object as
    being the same size
    when viewed at
    different distances
Perceptual Constancy
   shape constancy:
    seeing objects as
    having the same
    shape even when
    the image on the
    retina changes
Perceptual Constancy
   size-distance
    interacts with
       brain effortlessly
        calculates size of
        objects based on
Mueller-Lyer Illusion
Past Experiences and Perceptual Interpretation

   cataract: cloudiness in the eye’s 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
      cataracts developed later in life do not affect
The Thatcher Illusion
Past Experiences and Perceptual Interpretation

   This tendency to have
    a mental predisposition
    to perceive one thing
    and not another is
    known as a perceptual
       perceptual set
        determined by our
       schema: concept or
        framework that
        organizes and interprets
Past Experiences and Perceptual Interpretation

   Our past experiences guide our perceptions,
    but we can also adjust to radically new
    perceptions with time (perceptual
       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
Past Experiences and Perceptual Interpretation

   deficits to one sense can result in
    increased sensitivity of other senses
     blind musicians more likely than sighted
      ones to develop perfect pitch (Hamilton,
     with one ear plugged, blind people more
      accurate than sighted people at locating a
      sound source (Gougoux et al., 2005;
      Lessard et al., 1998)
   If a tree falls in the woods but nobody
    hears it, is there a sound?
     sound    waves created by a vibrating
        anytype 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.
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
Sound Waves
 sound intensity
  measured in decibels
    logarithmic measure
     of the volume of
     different stimuli as
     compared to a
     reference point
 prolonged exposure
  above 85 decibels can
  cause hearing damage
Structure of the Ear (pg. 213)
Structure of the Ear
   sound waves enter the
    ear and strike the
    eardrum (tympanic
   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
Structure of the Ear
   basilar membrane
    lined with tiny
    projections called hair
       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
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 piano’s keyboard)
                  volley principle
   primary auditory cortex in temporal lobe
       different pitches registered by different neurons
        within auditory cortex (like feature detectors in
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
       e.g. difference in onset of 0.000027 seconds can
        be distinguished
Hearing Without Awareness
   cocktail party phenomenon: the effect of not
    being aware of the content of other people’s
    conversations until your name is mentioned,
    then suddenly hearing it
       processing signal bottom-up, but top-down
        awareness isn’t 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. speaker’s gender)
             from ignored ear (Treisman, 1964)

   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)
   more than 28
    million Americans
    have hearing
       like color blindness,
        can be inherited or
            more than 30 genes
             have been linked to
             deafness (Lynch et
             al., 1997)
   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
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)
   molecules of certain
    substance sensed by
    about 5 million
    receptor fibers on the
    roof of each nasal
       different receptors for
        different smells, but not
        10,000 of them… (about
       Like colors, we detect
        smell by the
        combination of
        receptors that fire.
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)
Smell and Memory
   Why are smell and memory so closely
     evolutionaryexplanation: 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
     biologicalexplanation: two major neural
      tracks that deliver olfactory information
        one through thalamus to hippocampus
        other through limbic system (emotion)
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
   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)
   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)
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
       women more sensitive to touch than men
        (Weinstein, 1968)
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
Somasthetic Senses
   vestibular sense: the
    sense that provides
    information about
    the body’s
    orientation relative
    to gravity
       relies on semicircular
        canals in the inner
       filled with fluid and
        cilia (tiny hairs);
        detect balance by
        sensing fluid’s
   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
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
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
            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
Controlling Pain
 pain at the intersection of mind and body
    can be controlled by physical or psychological
 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
 Surgery patients whose rooms face trees require
  less pain medication and recover more quickly than
  those whose rooms face brick walls. (Ulrich, 1984)
Magnetic Sense
   Birds migrate using magnetic field of
    the Earth
     tinybits of iron in bird neurons involved in
      migration? (Gould, 1988; Kirschvink et al.,
   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...
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
       not actually part of ESP claims; doesn’t involve
        perception or knowing
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.”
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
   Are these results reliable?
       No... consistent failure to replicate ESP findings
       not known how brain would send or receive ESP
       What form would these signals take? (waves?
        chemicals? something else?)
 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
     upto 1 in 23 people experience
     synesthesia (Simner et al., 2006)
   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
   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)
   How do we know that synesthesia is
    real? Couldn’t 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)
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.
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)
Attention: The Gateway to Awareness
   Sometimes we are actively searching for
    specific objects...
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)
Attention: The Gateway to Awareness
 change blindness: failure to detect large changes in a
  visual scene
 Simons & Levin (1998)
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
     e.g.   Stroop effect
        name  the color of the ink used for each of the
        following words
Sensation and Perception Summary
 Sensory information is detected by the
  various senses (sensation), and
  interpreted and organized by the brain
 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.

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