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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