Chapter 4 -Physical Development in Infancy and Toddlerhood

Body Growth

• Height increases 50% by age 1, 75% by age 2
• Weight doubles by 5 months, triples by 1 year
• Individual and group differences in size and rate of growth

Individual and Group Differences in Growth

• Group differences:
  • male/female
  • ethnic
• Individual differences
• Skeletal age: best estimate of physical maturity

Growth Trends: Changes in Body Proportions

• Cephalocaudal
  • “Head to tail”
  • Lower part of body grows later than the head
• Proximodistal
  • “Near to far”
  • Extremities grow later than head, chest, and trunk

Neurons and Their Connective Fibers

• Neurons
  • Nerve cells that store and transmit information
• Synapses
  • Tiny gaps where fibers from different neurons come together but do not touch
• Neurotransmitters
  • Chemicals that are released by neurons and cross the synapse

Methods for Measuring Brain Functioning

• Electroencephalogram (EEG)
• Event-related potentials (ERPs)
• Functional magnetic resonance imaging (fMRI)
• Positron emission tomography (PET)
• Near-infrared spectroscopy (NIRS)

Regions of the Cerebral Cortex

• Prefrontal Cortex
  • Region of the cerebral cortex responsible for thought, especially:
    • consciousness
    • inhibition of impulses
    • integration of information
    • use of memory, reasoning, planning, and problem-solving strategies
  • Undergoes rapid growth in the preschool and school years, and in adolescence

Lateralization of the Cerebral Cortex

• Left Hemisphere
  • Verbal abilities
  • Positive emotion
  • Sequential, analytic processing
• Right Hemisphere
  • Spatial abilities
  • Negative emotion
  • Holistic, integrative processing

Brain Plasticity

• At birth, hemispheres have already begun to specialize
• Highly plastic cerebral cortex has high capacity for learning
• If part of cortex is damaged, other areas can take over its tasks
• Older children and adults retain some plasticity, but less than in young children

Sensitive Periods in Brain Development

• Appropriate stimulation is vital for brain growth
  • Experience-expectant growth: depends on ordinary experiences
  • Experience-dependent growth: additional growth resulting from specific learning experiences

Changing States of Arousal

• Sleep–wake pattern moves to night–day schedule during first year
• By age 2, total sleep time declines from 18 to 12 hours per day
• Sleep patterns are affected by social environment, cultural values

Influences on Early Growth

• Heredity
• Nutrition:
  • breastfeeding vs. bottle-feeding
  • risks of overfeeding

Benefits of Breastfeeding

• Correct balance of fat and protein
• Ensures nutritional completeness
• Helps ensure healthy physical growth
• Protects against disease

Malnutrition

• Marasmus (diet low in all essential nutrients)
  • Its consequence islasting physical damage; learning and behavioral effects; risk of death
• Kwashiorkor (diet very low in protein)
  • Its consequence is lasting physical damage; learning and behavioral effects
• Food insecurity
  • Its consequence is effects on physical growth; learning problems

Operant Conditioning

• Reinforcer
  • Increases probability that behavior will occur again by
  • presenting desirable stimulus
  • removing unpleasant stimulus
• Punishment
  • Reduces probability that behavior will occur again by
  • presenting unpleasant stimulus
  • removing desirable stimulus

Imitation

• Infants are born with
  primitive ability to imitate
• Mirror neurons provide biological explanation
• Powerful means of learning

Motor Development: Sequence and Trends

• Gross-motor development: crawling, standing, walking
• Fine-motor development: reaching, grasping
• Sequence is fairly uniform
• Large individual differences in rate of motor progress

Motor Skills as Dynamic Systems

• Mastery involves acquiring increasingly complex systems of action with each skill
• Each new skill is joint product of
  • central nervous system development
  • the body’s movement capacity
  • the child’s goals
  • environmental supports for the skill

Cultural Variations in Motor Development

• Rates and patterns of development affected by
  • early movement opportunities
  • environmental stimulation
  • child-rearing practices

Milestones of Reaching and Grasping

• Prereaching
• Ulnar grasp
• Transferring object from hand to hand
• Pincer grasp

Developments in Hearing

• 4-7 months
  • Sense of musical phrasing
• 6-7 months
  • Distinguishes musical tunes based
    on variations in rhythmic patterns
• 6-8 months
  • “Screens out” sounds not
    used in native language
• 6-12 months
  • Detects sound regularities
    in human speech
• 7-9 months
  • Begins to divide speech stream
    into wordlike units

Visual Development

• Supported by rapid maturation of eyes and visual centers in brain
• Improvements:
  • 2 months: focus
  • 4 months: color vision
  • 6 months: acuity, scanning, and tracking
  • 6–7 months: depth perception

Milestones in Depth Perception

• 3-4 weeks
  • Sensitivity to motion cues
• 2-3 months
  • Sensitivity to binocular depth cues
• 5-7 months
  • Sensitivity to pictorial depth cues

Milestones in Pattern Perception

• 2 months
  • Becomes sensitive to contrast in complex patterns; prefers them to simple patterns
• 2-3 months
  • Thoroughly explores a pattern’s features, pausing briefly to look at each part
• 3-4 months
  • Detects pattern organization, integrating pattern parts into organized whole

Milestones in Face Perception

• Birth- 1 month
  • Prefers simple facelike pattern to other stimuli
• 2-4 months
  • Prefers complex facial pattern
    to other complex stimulus arrangements
  •  Prefers mother’s detailed facialfeatures to another woman’s
• 3 months
  • Distinguishes features of different faces
• 5-12 months
  • Perceives emotional expressions
    on faces as meaningful wholes

Differentiation Theory

• Infants
  • actively search for invariant features of the environment
  • notice stable relationships among features of a stimulus, detecting patterns such as individual faces
  • gradually detect finer and finer features