Capacités perceptives
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Transcript of Capacités perceptives
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Chapter 4: Infancy: Early Learning, Motor Skills, and Perceptual Capacities (part 2)
February 2, 2005
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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
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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.
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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)
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Information from The Five Senses:Useful and usable information
SafetyPleasure
See
Smell
Hear
Taste
Touch
Falling objectMobile above crib
Smoke Mother’s scentCooking food
SirenA songMother’s voice
Spoiled foodMilk
A sharp pinA very hot object
A soft blanketMother’s touch
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Touch Present at birth: Newborns
Show palmar grasp HandleHandle smooth and textured objectssmooth 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
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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!
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Taste Development
Present before birth Strong preference for sweet tastes
Amniotic fluid Milk
Some decline in senior citizens Perception of sweetsweet and saltysalty tastes are well-preserved SourSour and bitterbitter 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 …
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Taste Reactions in Babies and Animals with Similar Physiology
Show characteristic facial movements in response to tastes
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SmellPresent
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
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Development of Smell
Prenatal olfaction:Prenatal olfaction: In the womb, can learn odors from their pregnant mother’s diet (Schall, Marlier & Soussignan, 2000)
a. Mom ate/ drank food or drinks flavored with anise
b-d. Moms didn’t
Smell: Learning Even Before Birth
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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
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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
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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
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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.
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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)
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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
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Testing for Red/Green Color Blindness
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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
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Infant Color Discrimination Task
Present babies with samples of the same color but different brightness can allow testing for color blindness
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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
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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
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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."
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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
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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
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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)
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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
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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
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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)
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Witness The Journey Home: A Romanian Adoption
CBC documentary about a Romanian orphans showed despite 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
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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.
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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)
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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