Transcript Physical Development in Infancy and Toddlerhood

Physical Development in Infancy and
Toddlerhood
Chapter 4
From pg. 133
Learning Capacities
 Learning – refers to changes in behavior as the result of
experience
 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
infants
 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
behavior
Steps of Classical Conditioning
1.
2.
3.
An unconditioned stimulus (UCS) produces a reflexive, or
unconditioned response (UCR)
A neutral stimulus, which does not lead to the UCR, is presented just
before, or at the same time as, the UCS
If learning has occurred, the neutral stimulus, now called the
conditioned stimulus (CS), will produced the reflex, now 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
 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
memory
 Habituate infants to a baby-
face
 Soon after show baby-face
and bald man
 Novelty preference –
infants remember baby-face
and look longer at bald man
 Assess infants’ delayed
memory
 Habituate infants to a baby-
face
 After weeks or months
show baby-face and bald
man
 Familiarity preference –
infants who continue to
remember baby-face look at
baby-face longer
Imitation
 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
make
 Mirror neurons underlie these capacities
 Specialized cells in the motor areas of the cortex
 Fire identically when a primate hears or sees an action and when it does the action
itself
 Allow us to observe another person’s behavior while simulating the behavior
mentally
 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
age
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
move 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
produced
 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
age
 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
Development
 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 &
Grasping
 Voluntary reaching may play the greatest role in infant
cognitive development
 Because it opens up a whole new way of exploring the
environment
 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
opposably
Hearing Development
 Shift from sensation to perception
 Sensation – passive, what baby’s receptors detect when exposed to
stimulation
 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
they begin to avoid the deep
side and react with fear
 Meaning they perceive the
drop-off
 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
depth
 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, they prefer the one with more contrast
To adults the
complex
checkerboard has
more contrasting
elements
Because of their
poor vision,
newborns cannot
resolve the small
features in the
complex pattern
Milestones in Pattern Perception
1 month
• Poor contrast sensitivity; prefer single, large
simple patterns with high contrast
2-3
months
• Can detect detail in complex patterns
• Scan internal features of patterns
4
months
Can detect patterns even if boundaries are not
really present
12
months
Can detect objects even if two-thirds of drawing
is missing
4 months
12 months
Face Perception
 Infants’ tendency to search for structure also applies to face
perception
 Birth-1month – prefer simple facelike patterns to other
patterns
 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
relationships
Intermodal Perception
 Intermodal stimulation – simultaneous input from
multiple senses
 Intermodal perception – perceiving running streams of
light, sound, tactile, odor, and taste information as unified
wholes
 Infants perceive input from different sensory systems 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 differentshaped 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 parentinfant interaction
Understanding Perceptual
Development
 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