Physical Development in Infancy and Toddlerhood - Ashton Southard by fjzhangweiyun


									Physical Development in Infancy and
              Chapter 4
             From pg. 133
Learning Capacities
 Learning – refers to changes in behavior as the result of
   Babies are born with built-in learning capacities
 Types of infant learning
   Classical conditioning
   Operant conditioning
   Habituation
   Imitation
Classical Conditioning
 Newborn reflexes allow classical conditioning in young
   Neutral stimulus is paired with a stimulus that leads to a
    reflexive response
   Once the baby’s nervous system makes the connection between
    the two stimuli, the neutral stimulus alone with produce the
     Steps of Classical Conditioning
1.   An unconditioned stimulus (UCS) produces a reflexive, or
     unconditioned response (UCR)
2.   A neutral stimulus, which does not lead to the UCR, is presented just
     before, or at the same time as, the UCS
3.   If learning has occurred, the neutral stimulus, now called the
     conditioned stimulus (CS), will produced the reflex, cow called a
     conditioned response (CR)
Operant Conditioning
 Form of learning in which infants act on the environment and stimuli
  that follow their behavior change the probability that the behavior will
  occur again
    Reinforcer – increases probability that the behavior will occur again
      Ex. Sweet liquid reinforces the sucking response in newborns
    Punishment – decreases probability that the behavior will occur again
      Ex. Sour-tasting liquid punishes newborns’ sucking response, causing them to purse
       their lips and stop sucking entirely
 Vital to the formation of social relationships
    Baby gazes into adult’s eyes, adult smiles back, infant looks and smiles again
    Behavior of each partner reinforces the other so that both continue the
     pleasurable interaction
    Contributes to development of infant-caregiver attachment
 Habituation – gradual reduction in the strength of a
  response due to repetitive stimulation
   Babies respond more strongly to novelty
   After baby has seen a stimulus over and over it is no longer
    novel and baby will decrease responding (lose interest)
   Looking, heart rate, and respiration may all decline, indicating a
    loss of interest
 Recovery – new stimulus, or a change in the environment,
  causes responsiveness to return to a high level
 Assess infants’ recent
    Habituate infants to a baby-
    Soon after show baby-face
     and bald man
    Novelty preference – infants
     remember baby-face and
     look longer at bald man
 Assess infants’ delayed
    Habituate infants to a baby-
    After weeks or months
     show baby-face and bald
    Familiarity preference –
     infants who continue to
     remember baby-face look at
     baby-face longer
 Infants learn through copying the behavior of others
    Certain gestures, head movements, facial expressions
    Across all cultures as well as newborn chimpanzees
 Some researchers believe newborns imitate in the same was as older children
  and adults
    By trying to match the body movements they see with the ones they feel themselves
 Mirror neurons underlie these capacities
    Specialized cells in the motor areas of the cortex
    Fire identically when a primate hears of sees an action and when it does the action
    Allow us to observe another person’s behavior while simulating the behavior
    Biological basis for of imitation, empathetic sharing of emotions, and understanding
     other’s intentions
    Brain-imaging research suggests mirror neurons function as early as 6 months of
Motor Development
 New motor skills allow babies to explore their bodies and
  environment in new ways
   Sitting upright gives a new perspective on the world
   Reaching permits ability to act on objects
   When infants can move on their own, their opportunities for
    exploration multiply
Sequence of Motor Development
 Gross-motor development – actions that help an infant more
  around the environment
   Crawling, standing, walking
 Fine-motor development – smaller movements
   Reaching and grasping
 Sequence of motor development is fairly uniform across children,
  but there are large individual differences in rates of progress
 Cephalocaudal trend – motor control: control head 1st, control
  arms and trunk 2nd, control legs 3rd
 Prodimodistal trend – head, trunk, and arm control appears
  before coordination of the hands and fingers
Motor Skills as Dynamic Systems
 Dynamic systems theory of motor development
   Mastery of motor skills involves acquiring increasingly complex
    systems of action
   When separate motor skills work as a coordinated system, more
    effective ways of exploring and controlling the environment are
   Example: control of the head and upper chest combine into
    sitting with support
Motor Skills as Dynamic Systems
 Each new skill is a joint product of:
      Central nervous system development
      The body’s movement capacities
      The child’s goals
      Environmental supports for the skill
 Physical environment strongly influences motor skills because it
  provides opportunities for exploration
    Ex. Infants in homes with stairs learn to crawl up stains at an earlier
 Motor development cannot be genetically determined because it is
  motivated by exploration and the desire to master new tasks
 Behaviors are softly assembled, allowing for different paths to the
  same motor skill
Dynamic Motor Systems in Action
 Researchers have discovered that the way babies acquire motor
  capacities depends on:
   The anatomy of the body part in use
   The surrounding environment
   The baby’s efforts
 Means that acquiring motor capacities is not strictly cephalocaudal
   Ex. 8 month old babies may reach for a toy with their feet before they
     will reach with their hands
      Because the hip joint constrains the legs to move less freely than the shoulder
       constrains the arms
      Makes reaching with arms more difficult, requiring much more practice than
       reaching with feet
Cultural Variations in Motor
 Cross-cultural research shows how early movement opportunities
  and a stimulating environment contribute to motor development
 Example: infants in Iranian orphanages were deprived of
  surroundings that induce infants to acquire motor skills
   Spent their days lying on their backs in cribs with no toys
   Most did not move on their own until after 2 years of age
   When they did move, constant experience of lying on their backs
    caused them to scoot in a sitting position rather than crawl
   Because babies who scoot come up against furniture with their feet,
    not their hands, they are less likely to pull themselves to a standing
    position (which prepares them for walking)
   At 3 to 4 years old, only 15% could walk on their own
Fine-Motor Development: Reaching &
 Voluntary reaching may play the greatest role in infant
  cognitive development
   Because it opens up a whole new way of exploring the
   Grasping things, turning them over, and seeing what happens
    when they are released allows infants to learn a great deal about
    the sights, sounds, and feel of objects
 Reaching and grasping start out as gross activities and move
  toward mastery of fine movements
    Milestones of Reaching and Grasping
 Prereaching (newborn-3 months)
   poorly coordinated swipes or swings
 Reaching (3 – 4 months)
   Ulnar grasp – clumsy motion in which the fingers close against
    the palm
   first with both hands, then with one
 Transfer object from hand to hand (4 – 5 months)
 Pincer grasp (9 months)
   More coordinated grasp using the thumb and index finger
Hearing Development
 Shift from sensation to perception
    Sensation – passive, what baby’s receptors detect when exposed to
    Perception – active, organize and interpret what is perceived
 4-7 months – sense of musical phrasing
    Prefer structured musical sounds
 6-8 months – “screen out” sounds from non-native languages
    Learn to focus on meaningful sound variations
 7-9 months – extend sensitivity to speech structure
    Recognize familiar words
    Natural phrasing in native language
    Begin to divide the speech stream into wordlike units
Analyzing the Speech Stream
 Statistical learning capacity – ability to analyze speech for
  recurring sequences of sounds and extract patterns from
  complex continuous speech
   By analyzing the speech stream for patterns infants acquire a
    stock of speech structures
   Later, infants will learn the meaning of the familiar speech
    structures they have stored
 Because communication is multisensory, infants receive
  support from other senses in analyzing speech
   Example: parents teaching infant the word “doll”
     Saying “doll” while moving a doll around and sometimes having the doll
      touch the infant
Vision Development
 Supported by rapid maturation of the eye and visual centers
  in the cortex
 2 months – can focus on objects about as well as adults
 4 months – color vision
 6 months – visual acuity (fineness of discrimination) 20/20
   Scanning the environment and tracking moving objects
     Result of increased ability to control eye movements

 6-7 months – depth perception
   Ability to judge the distance of objects from one another and
    from ourselves
Depth Perception: The Visual Cliff
 Plexiglas-covered table
   Shallow side
   Deep side
 Mother stands on deep side
  and calls infant
 Around the time babies crawl
  the begin to avoid the deep
  side and react with fear
   Meaning they perceive the
 Babies figure out how to use
  depth cues from repeated
  everyday movements
Milestones in Depth Perception
 3-4 weeks old – motion perception
   Blink eyes defensively when an object moves toward their face as if it
    is going to hit
 2-3 months – binocular depth
   Occurs because our eyes have slightly different views of the visual
    field and the brain blends the two images, resulting in perception of
 6-7 months – pictorial depth & fear of heights
   Ex. Receding lines, changes in texture, overlapping objects, shadows
    cast on surfaces
   Pattern Perception
 Contrast sensitivity
     Contrast – the difference in the amount of light between adjacent
      regions in a pattern
     If babies are sensitive to (can detect) the contrast in two or more
      patterns, the prefer the one with more contrast

To adults the                                                   Because of their
complex                                                         poor vision,
checkerboard has                                                newborns cannot
more contrasting                                                resolve the small
elements                                                        features in the
                                                                complex pattern
Milestones in Pattern Perception
             • Poor contrast sensitivity; prefer single, large
1 month
             simple patterns with high contrast
  2-3        • Can detect detail in complex patterns
 months      • Scan internal features of patterns
   4         Can detect patterns even if boundaries are not
 months      really present
  12         Can detect objects even if two-thirds of drawing
 months      is missing

  4 months                                 12 months
Face Perception
 Infants’ tendency to search for structure also applies to face
 Birth-1month – prefer simple facelike pattern to other
 2 months – can discriminate faces
   recognize and prefer mothers’ detailed facial features to those
    of an unfamiliar woman
 3 months – make fine distinctions among the features of
  different faces
 Perception of the human face supports infants’ earliest social
Intermodal Perception
 Allows us to make sense of intermodal stimulation
   Intermodal stimulation – simultaneous input from multiple
 Intermodal perception – perceiving running streams of light,
  sound, tactile, odor, and taste information as unified wholes
 Infants perceive input from different sensory system in a
  unified way by detecting amodal sensory properties
   Amodal sensory properties – information that overlaps two or
    more sensory systems
      Such as rate, rhythm, duration, intensity, temporal synchrony (vision and
       hearing), and texture and shape (vision and touch)
Milestones in Intermodal Perception
 Birth-3 months – can detect amodal sensory properties
   Ex. After touching an object placed in the palm, infants
    recognize it visually and can distinguish it from a different-
    shaped object
 3-4 months – can relate speech sounds to lip movement
 4-6 months – can perceive unique face-voice parings of
  unfamiliar adults
 8 months – can match voices and faces on the basis of gender
 Intermodal perception facilitates social and language
  processing and is encouraged and expanded by early parent-
  infant interaction
Understanding Perceptual
 How do all these developments occur so rapidly???
 Differentiation theory – infants actively search for invariant
  features of the environment (those features that remain stable)
  in a constantly changing perceptual world
   1st – search for invariant, stable features in the environment
   2nd – note stable relationships between features
     Visual patterns, intermodal relationships
   3rd – gradually detect finer and finer features
     Differentiation – analyze or break down invariant features
 Think of perceptual development as a built-in tendency to
  search for order and consistency which becomes increasingly
  fine-tuned with age

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