Chapter 4 Physical Development in Infancy and Toddlerhood

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Chapter 4Physical Development in Infancy and
Toddlerhood

• Development Through the Lifespan
• 2nd edition Berk

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BODY GROWTH

• Changes in Body Size and Muscle Fat
• (0 to 2 years)
• Physical growth is rapid.
• Length increases 50 percent by first year, 75
  percent by second.
• Weight doubles at 5 months, triples by first
  year, and quadruples by the second.
• Gains occur in growth spurts.
• Early rise in baby fat until 9 months
• Helps keep a constant body temperature
• Toddlers become more slender.

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Individual and Group Differences

• Skeletal age
• Measure of bone development
• Best way to measure physical development
• Girls are slightly shorter and lighter and have a
  higher ratio of fat to muscle.
• Ethnic differences in size and rate of growth
• Developmental problems and mortality rates vary
  by gender and race.

Figure 4.1
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BRAIN DEVELOPMENT
Birth

• Neurons
• At birth, the brain is nearer its adult size than
  any other physical structure.
• 100 to 200 billion neurons
• Synapses
• Tiny gaps between neurons
• Neurons release chemicals that send messages
• Synaptic pruning
• Unused neurons die off.
• Myelinization
• Neural fibers are coated with fatty insulation.
• Glial cells myelinate.

Six months
Two years
Figure 4.3
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The Cerebral Cortex

• 85 percent of brain weight, and last to stop
  growing
• Different regions have specific functions.
• Frontal lobes (thought) develop later.
• Lateralization
• Specialization of hemispheres in cortex
• Brain plasticity
• Ability of part of brain to take over function of
  damaged part

Figure 4.4
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Sensitive Periods of Development

• Stimulation is vital during growth spurts, which
  occur from infancy to early adulthood.
• Experience "wires" a child's brain growth.
• Understimulation impairs development.
• Possible to overwhelm children
• Note new brain research

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INFLUENCES ON PHYSICAL GROWTH

• Heredity largely determines height and rate of
  physical growth.
• Catch-up growth
• Heredity and nutrition determine weight.
• Emotional well being as a factor
• Non-organic failure to thrive related to small
  size and cognitive or emotional problems

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Nutrition

• Babys energy needs twice those of an adult.
• 25 percent of infant's calories are devoted to
  growth.
• Breast- versus bottle-feeding
• Correlation between fatness in infancy and
  obesity at older ages.
• Malnutrition impedes growth and brain development
  ( 40-60 of worlds children)

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LEARNING CAPACITIES

• Classical Conditioning
• Reflexes allow classical conditioning in young
  infants.
• Extinction is a decline in the CR as a result of
  presenting the CS without the UCS.

Figure 4.5
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LEARNING CAPACITIES

• Operant Conditioning
• Spontaneous behavior is followed by a reinforcer.
• Changes the probability that the behavior will
  occur again
• Punishment
• Removing a desirable stimulus or presenting of an
  unpleasant one to decrease the occurrence of a
  response
• Young babies are active learners.

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LEARNING CAPACITIES

• Habituation
• Gradual reduction in the strength of a response
  due to repetitive stimulation
• Dishabituation
• Recovery of responsiveness after stimulation
  changes
• Imitation
• Copying the behavior of another person
• Newborns can imitate facial expressions and head
  movements.

Figure 4.6
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MOTOR DEVELOPMENT

• Gross motor development
• Crawling, standing, and walking
• Fine motor development
• Reaching and grasping
• Individual differences in rate of motor progress
• Cephalocaudal trend
• Proximodistal trend

Table 4.1
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Motor Skills as Dynamic Systems

• Mastery of motor skills involves acquiring
  increasingly complex dynamic systems of action.
• New skills are a joint product of
• Central nervous system development.
• Movement possibilities of the body.
• Environmental supports for the skill.
• Motivation of the child.
• Note Cultural variations in environment

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Fine Gross Motor Development

• Voluntary reaching and cognitive progress
• Role of perception (e.g. visual)
• Gross motor progression - lifting head,sitting,
  standing, cruising, walking
• Body balance, motor control and refinement of
  fundamental movement patterns

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Fine Motor Development

• Motor skills go from gross to finer movements.
• Prereaching
• Uncoordinated, primitive
• Ulnar grasp
• Clumsy, fingers close against palm
• Tripod pincer grasps
• Coordinated use of forefinger and thumb

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PERCEPTUAL DEVELOPMENT

• Hearing
• Sound supports visual and tactile exploration.
• Ability to identify location of sound improves
  over the first 6 months.
• By 6 months, babies "screen out" sounds not used
  in their language.
• By 6 to 12 months, infants focus on larger speech
  units critical for meaning.

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Vision

• By 2 months, infants focus on objects and
  discriminate colours well.
• By 11 months, visual acuity reaches a near-adult
  level.
• Independent movement promotes depth perception
  -new level of brain organisation

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Vision

• Depth Perception
• Crawling infants distinguish deep and shallow
  surfaces and avoid dangerous-looking drop-offs.
• Emergence of depth perception
• Motion is the first depth cue.
• Binocular sensitivity (2 to 3 months)
• Pictorial depth perception ( 6 months)

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Vision

• . Pattern and Face Perception
• Newborns prefer patterned to plain stimuli.
• Contrast sensitivity
• Babies prefer more contrast.
• Face perception becomes more refined by 3 mths

Figure 4.10
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Intermodal Perception

• Intermodal perception combines information from
  more than one modality.
• Babies perceive the world in an intermodal method.

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UNDERSTANDING PERCEPTUAL DEVELOPMENT

• Differentiation Theory (Eleanor and James Gibson)
• Perceptual development involves detection of
  fine-grained, invariant features in the
  environment.
• Other researchers believe babies impose meaning
  on what they perceive, constructing categories of
  objects and events.
• Many researchers combine the two viewpoints.