Capacités perceptives
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Capacités perceptives

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Capacités perceptives Capacités perceptives Presentation Transcript

  • Chapter 4: Infancy: Early Learning, Motor Skills, and Perceptual Capacities (part 2) February 2, 2005
  • Today’s lecture: Perceptual Development in Infancy
    • Why study babies’ perception?
    • The five senses
      • Touch
      • Taste
      • Smell
      • Hearing
      • Vision
        • Depth perception
        • Patterns
        • Object perception
    • Balance
    • Intermodal perception
    • Deprivation and sensitivity
  • Why study infant perception?
    • Motor and perceptual development go together
    • Implications for one’s theory of development
      • Nature vs. Nurture
        • If early evidence, points to one or the other, that’s probably your theory (probably doesn’t make sense to switch)
    • Implications for later development
      • Language
      • Social
      • Cognitive
      • Etc.
  • Studying Babies’ Perceptual Development
    • Babies can’t directly communicate perceptions
    • Research requires careful design of stimuli and experimental paradigm
      • beware of parental influences
      • not all methods are suitable
    • Methods
      • Preferential looking
      • Habituation
      • Observable behaviors (e.g., facial expressions, crawling)
  • Information from The Five Senses: Useful and usable information Safety Pleasure See Smell Hear Taste Touch Falling object Mobile above crib Smoke
    • Mother’s scent
    • Cooking food
    Siren
    • A song
    • Mother’s voice
    Spoiled food Milk
    • A sharp pin
    • A very hot object
    • A soft blanket
    • Mother’s touch
  • Touch
    • Present at birth: Newborns
      • Show palmar grasp
      • Handle smooth and textured objects differently (Molina & Jouen, 2003).
    • Interaction between baby and caregiver
      • Essential for normal development
      • Evidence from human babies and also animal research
    • Sensitivity
      • Newborn is sensitive to tactile stimulation
        • Preemies
          • Isolated to keep germs away and temperature constant
          • “ Touch therapy” (Field et al., 1986)
            • Study of preemies (they were on average 9 weeks early)
            • Facilitated growth, weight gain
            • Better NBAS results (than control group)
            • Shorter hospital stays
        • Baby massage
  • Developmental Changes in Touch
    • Develops over time
        • Different than adults in some ways …
    • Somatosensory acuity declines with age (Stevens & Choo, 1997): - increased 2-point thresholds with age - hands, feet, and face show a sharper decline
    Big toe: 400% drop in sensitivity! Fingertip: 130% drop in sensitivity!
  • Taste
    • Development
      • Present before birth
      • Strong preference for sweet tastes
        • Amniotic fluid
        • Milk
    • Some decline in senior citizens
      • Perception of sweet and salty tastes are well-preserved
      • Sour and bitter sensations decline with age
    • Babies can be conditioned to flavors
      • With hunger
      • Maybe some would like spinach sooner …
    • Facial expressions give evidence to babies’ preferences …
  • Taste Reactions in Babies and Animals with Similar Physiology
    • Show characteristic facial movements in response to tastes
  • Smell
    • Present
      • Before & at birth
      • Increases rapidly
      • Like other senses, decreases in old age
    • Same discriminations as adults
      • Learning
        • Recognition of familiar smell (adaptive)
          • Preference for mother over another mother
  • Development of Smell Prenatal olfaction: In the womb, can learn odors from their pregnant mother’s diet (Schall, Marlier & Soussignan, 2000)
    • Mom ate/ drank food or drinks flavored with anise
    • b-d. Moms didn’t
    Smell: Learning Even Before Birth
  • Balance and Self-movement
    • The postural system must meet 3 main challenges (from Dwyer, 2005) 
      • maintain steady stance ( balance ) in the presence of gravity
      • generate responses that anticipate volitional goal-directed movements
      • be adaptive – integrating posture/balance with voluntary movement
    • 3 sources of information
      • Proprioceptive stimulation (from skin, muscles, and joints)
      • Vestibular stimulation (from inner ear)
      • Optical flow stimulation (from visual field)
    • Babies react to perception of movement affecting their balance
  • Hearing
    • Present well before birth
    • Newborns orient towards sounds
      • As long as sounds are not too loud or too brief – rattle works well
      • But hearing still not completely adult-like
        • Babies may hear echoes when adults’ ears would filter out a very quickly repeated sound
    • Strong auditory preferences:
      • Women>men
      • Mother>other women
      • Father=other men
      • Heartbeat> man
      • Mom’s voice altered to sound like it did in utero> Ms voice outside**
        • Evidence for prenatal learning
  • Sound Localization
    • Cues
    • Difference in loudness of the two sounds created by the "sound shadow" of the head. 
      • Important for higher pitched sounds (above about 3000 Hz).
    • Difference in the time of arrival of the sound to the two ears (or the phase difference). 
      • Important for lower pitched sounds (below about 3000 Hz).
    • Below -- sound louder and sooner to left ear
    L R
  • Hearing: Differences between infants and adults
    • The smaller size of an infant's head influences sound localization: 
    • means that the time difference between the ears will be less for infants than adults.
    • may also increase the pitch at which loudness differences are an effective cue
      • Reduced ability to localize sounds
      • But not an inability to localize sounds.
  • Vision
    • Berk, “Humans depend on vision more than any other sense for active exploration of the environment. Yet vision is the least mature of the baby’s senses.”
      • Most complex sense in humans
      • Humans rely on vision more than many (but not all) other animals
      • Takes the longest to become “adult-like”
    • Limitations
        • Newborn’s visual world lacks in sharpness, detail, color…
        • Cannot be corrected but by natural development improves rapidly (much improved already by 3-4 mos)
  • Development of Vision
    • Vision very poor at birth
      • Poor acuity – detail vision
        • Smallest stripes newborn can see are 30X wider than adult (adult 20/20, NB 20/600 – legally blind!)
      • Mostly fixed accommodation
        • Lens of eye unable to change shape
        • Optimal viewing at about 12”, but still blurry even there
        • Little or no ability to accommodate to changing distances
          • Able to see somewhat from about 8 to 15”
      • Very difficult to test at this age, so data limited
    • Rapidly improves after birth
      • Range of accommodation almost at adult levels by 3 months (Banks, et al, 1980)
        • Much easier to test by this age – more accurate and complete data
        • Testing based in preference for looking at a pattern over uniform surface
  • Testing for Red/Green Color Blindness
  • Can Infants discriminate color?
    • Poor color vision…
      • Newborn can tell red vs. green, but not yellow vs. red or green
      • Improves rapidly, by 3-4 mos color vision is adult-like
    • Problem in determining color discrimination
      • Color and Brightness are two independent aspects of any image
      • Confounding color differences with brightness differences
        • Are infants (or adults) discriminating differences on brightness or color?
        • Brightness is a perceptual characteristic not simply a physical characteristic– must be determined by testing vision
      • Solution – in adults
        • 1) Have adults match different colors for brightness
        • 2) Compare different colors previously matched for brightness
  • Infant Color Discrimination Task
    • Present babies with samples of the same color but different brightness can allow testing for color blindness
  • Depth Perception
    • Judging absolute vs. relative distances
      • Absolute: judgment involves assessing the true distance of a single object
      • Relative: distance refers to assessing distance of one object compared to some other object
    • Sensitivity to Depth Cues
      • Kinetic - image moving or not (relative to your eyes)
      • Binocular - one or two eyes
      • Pictorial – lines, texture, overlap
    • Cues may develop at different rates
  • Crawling and Depth
    • Depth perception takes time to develop
      • Safety gates by stairs
      • Requires experience with environment
        • Baby’s posture affects their reading of cues
        • Visual cliff
          • A means of testing babies’ depth perception
  • Vision: Blindness
    • Motor exploration and spatial understanding
      • Iverson (1998) studied congenitally blind children
        • Some gesture when giving directions
        • Talking about changes in objects, quanities
        • The relation between speech and gesture different than for sighted kids
          • Blind kids gave longer and more detailed directions (e.g., more landmarks)
          • "And what both blind and sighted children tend to do is accompany that phrase with a gesture where it looks like they're holding a container in their hand and pouring at the same time," she says. "The blind and sighted kids gestured at the same rate and their gestures looked remarkably like one another."
  • Pattern Perception
    • Contrast sensitivity
      • Prefer higher contrast
        • Lower contrast, complex displays a blur
        • Mobile at right
    • By end of infancy
      • Can process multiple pattern elements
      • Use adult-like cues
    • Face perception
      • Babies learn and prefer face-like patterns
      • By a few months old can differentiate familiar from unfamiliar pictures of faces
  • Object Perception
    • Shape constancy
      • Emerges early
    • Object unity
      • Johnson (et al.)
        • compared how 2- and 4-month old infants processed displays of moving partially occluded object (a rod behind a box, like in Berk Figure 4.19 [same scientist, newer study] )
        • unlike 2-month olds, 4-month olds’ reactions more reliably indicated perceptions of 2 pieces as one
          • Piecing together parts
  • A new(er) view of infant perceptual development
    • Johnson (of NYU)
    • Johnson: "It is now clear that theories of innate knowledge do not hold up under scrutiny. (…) perceptual development in infants emerges from a combination of experience and brain development.”
    • “ Another implication of these findings is that infants do not necessarily benefit in any meaningful way from stimulating toys or exercises. Babies learn these concepts quickly through visual observation rather than enrichment, direct instruction, or manual object manipulation. (…) Social interaction, however, is a different story--infants benefit greatly from one-on-one time with other people."
    • NYU study provides new view of infant perceptual development ( http:// www.medicalnewstoday.com/medicalnews.php?newsid =16153 , 10 Nov 2004)
  • Intermodal Perception
    • Linking two or more modes of input (sight + sound, touch + sight, etc.)
      • Mother’s voice goes with sight of mother, smell of mother, touch of mother, food from mother
    • Processing information in a rich context
  • Understanding Perceptual Development
    • Differentiation
      • Searching for invariant features , greater and greater detail
        • Where are meaningful differences, similarities
        • Forming ideas, “concepts”
    • Affordances
      • “ the action possibilities a situation offers an organism with certain motor capabilities”
      • What an object can do or have done to it from its characters
  • Early Deprivation and Enrichment
    • Infancy as a sensitive period
      • Evidence from Romanian orphanages (and other orphanages)
        • Similar with babies neglected by their birth families cannot be studied in such a large-scale way
        • Often conditions pre-adoption/ pre-neglect are not well-known
        • Gradual “catch-up” possible
          • If adopted early enough (see below)
  • Witness The Journey Home: A Romanian Adoption
    • CBC documentary about a Romanian orphans showed d espite attention and action Romanian orphanages
      • Many thousands of children still in orphanages today
      • Orphanages still understaffed
      • The Romanian children
        • had spent an average of 17.5 months in an orphanage (almost their entire lives)
        • most did not have enough to eat, 56% not enough to drink at the orphanage
        • most had spent 18 - 20 hours a day lying quietly in their cribs
    • Romanian orphans typically had
      • Medical Problems
      • Developmental Problems 
      • Behavioral Problems 
    • From a CBC documentary: Source http://www.tv.cbc.ca/witness/rom/rommain.htm
  • Factors Leading to the Best Results in Canada
    • Romanian Adoption Study by Simon Fraser University : - less time spent in the orphanage - only one Romanian child adopted by the Canadian family - an older mother
    • - less family stress in Canada
    • Although more than one third of the Romanian orphans recovered fully from the neglect they experienced in early childhood, the study's authors recommended that all children adopted from orphanages be considered 'special needs' children.
  • Early Stimulation & Learning
    • Need reasonable expectations
      • Overstimulation may not be effective
      • Readiness
        • Even for non-delayed children
          • Probably can’t create “baby geniuses”)
          • Probably won’t hurt to use
            • But quite possibly unrealistic to expect too much, spend much time
            • And still need to be developmentally sound:
            • Although most customer feedback positive, one customer commented: “I, however, have a few issues with this video (…) My son is learning which animals make which sounds, but here's this dog mooing and oinking and meowing. I also have to wonder if it is a good idea to show toddlers the clip of the mice having a food fight. I have a hard enough time getting my son to keep his food on his tray! (…).” (http://www.priceclash.com/baby-einstein-neighborhood-animals)
  • Summary: Infancy
    • Consider how motor and perceptual development influence each other
    • A purely Nature theory of development is not tenable
    • Early preferences, fears, aversions may have lasting effects
      • Behaviorists
      • Freudian theorists
    • More later in terms of
      • language
      • cognition
      • emotional development