PHYSICAL DEVELOPMENT
IN INFANCY
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Chapter 5
PATTERNS OF GROWTH
• Cephalocaudal: The sequence in which the
earliest growth always occurs at the top—the
head—with physical growth and feature
differentiation gradually working from top to
bottom
• Proximodistal: Growth starts at center of body
and moves toward extremities
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FIGURE 5.1 - CHANGES IN PROPORTIONS
OF THE HUMAN BODY DURING GROWTH
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HEIGHT AND WEIGHT
• Average North American newborn is 20 inches
and 7½ pounds
• Weight doubles at about 5 months; triples by first birthday
• Height increase at least 50% in first year
• Average 2-year-old
• 26 to 32 pounds and 32 to 35 inches tall
• Growth rate considerably slower in second year
• Growth appears continuous but actually occurs in
spurts
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BRAIN DEVELOPMENT
• The brain is the command center of organism
• Extensive growth in utero and infancy
• Brain of neonate weighs less than one pound
• By first birthday, the brain triples in weight, reaching nearly
70% of adult weight
• EEG shows brain activity spurt from 1½ to 2
years of age
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MAPPING THE BRAIN
• Forebrain: The region of the brain that is
farthest from the spinal cord and includes the
cerebral cortex and several structures beneath it
• Cerebral cortex: Tissue that covers the
forebrain like a wrinkled cap and includes two
halves, or hemispheres
• Lateralization: Specialization of function in
one hemisphere of the cerebral cortex or the
other
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FIGURE 5.3 - THE HUMAN BRAIN’S
HEMISPHERES
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WHAT ARE NEURONS?
• Basic unit of nervous system
• Receive and transmit messages
• Neurons vary according to function and location, but
all contain
• Cell Body
• Dendrites
• Axon
• Neurotransmitters
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FIGURE 5.5 - THE NEURON
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HOW DO NEURONS DEVELOP?
• As child matures
• Axons grow in length
• Dendrites and axon terminals proliferate
• Connection networks become more complex
• Myelin
• Makes messages more efficient
• Myelination occurs with maturation
• Inhibition of myelination results in disease
• Multiple sclerosis
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BRAIN DEVELOPMENT
• Blooming and pruning
• Synaptic overproduction peaks about 4 months
after birth
• Prefrontal cortex overproduction peaks about 3
year of age
• Adult density achieved in adolescence
• Heredity and environment affect timing
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FIGURE 5.6 - THE DEVELOPMENT OF
DENDRITIC SPREADING
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FIGURE 5.7 - SYNAPTIC DENSITY IN THE HUMAN
BRAIN FROM INFANCY TO ADULTHOOD
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EARLY EXPERIENCE AND THE
BRAIN
• The brain demonstrates both flexibility and
resilience
• Neuroscientists believe that what wires the brain
is repeated experience
• Neuroconstructivist view: Biological processes
and environmental conditions influence the
brain’s development
• The brain has plasticity and is context dependent
• Brain development is closely linked with cognitive
development
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SLEEP
• Infants 0 to 2 years of age slept an average of
12.8 hours a day
• With a range of 9.7 to 15.9 hours
• The most common infant sleep-related problem
reported by parents is nighttime waking
• Infant nighttime waking problems have
consistently been linked to excessive parental
involvement in sleep-related interactions with
their infant
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REM (RAPID EYE MOVEMENT)
SLEEP
• The eyes flutter beneath closed lids
• In non-REM sleep, this type of eye movement
does not occur and sleep is quieter
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FIGURE 5.10 - DEVELOPMENTAL CHANGES
IN REM AND NON-REM SLEEP
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SHARED SLEEPING
• Culture and Sleeping Arrangements
• Sharing bed common in many cultures
• Crib/separate room common in U.S.
• American Academy of Pediatrics discourages cosleeping because of stress and SIDS risk
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SUDDEN INFANT DEATH
SYNDROME (SIDS)
• Infant stops breathing, usually during night, and
dies without apparent cause
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Highest cause of infant death in U.S.
Highest risk is 2 to 4 months of age
Prone position reduces risk
Less common in bedroom with fan and infant who
sleeps with pacifier
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NUTRITION
• Healthy infants need
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Loving, supportive feeding environment
50 calories per day per pound of weight
Breast milk (nature’s food)
Gradual increase of chew-and-swallow
More fruits and vegetables, less junk food
Demand feeding becoming more popular
Poor dietary patterns can cause overweight
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BREAST VERSUS BOTTLE
FEEDING
• Breast milk
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Fewer gastrointestinal infections
Lower respiratory tract infections
Reduces effects of asthma in first 3 months
Reduce risk of skin inflammation
May lessen likelihood of obesity
Lowers risk of childhood and adult diabetes
Less risk of experiencing SIDS
Claims of no link to allergy prevention
Claims of no links to children’s cognitive development
and cardiovascular system
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EVALUATION OF BENEFITS FOR
THE MOTHER
• There is lower incidence of breast cancer in
women who breast feed their infants
• Reduction in ovarian cancer in women who
breast feed their infants
• Small reduction in type 2 diabetes in women
who breast feed their infants
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MALNUTRITION IN INFANCY
• Early weaning can cause deficiencies
• Infants can develop:
• Marasmus: A wasting away of body tissues in the
infant’s first year, caused by severe protein-calorie
deficiency
• Kwashiorkor: A condition caused by a severe
deficiency in protein in which the child’s abdomen and
feet become swollen with water
• Usually appears between 1 to 3 years of age
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HEALTH
• Immunization begins in infancy
• Accident prevention
• Increased monitoring needed in infancy
• Most common accidents in infancy
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Aspiration of foreign objects
Suffocation
Falls
Poisoning
Burns
Motor vehicle accidents
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DYNAMIC SYSTEMS THEORY
• Dynamic systems theory: The perspective on
motor development that seeks to explain how
motor skills are assembled for perceiving and
acting
• When infants are motivated to do something, they might
create a new motor behavior
• Mastering a motor skill requires the infant’s active
efforts to coordinate several components of the skill
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REFLEXES
• Built-in reactions to stimuli that govern the
newborn’s movements, which are automatic and
beyond the newborn’s control
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Rooting
Sucking
Moro
Babinski
Grasping
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GROSS MOTOR SKILLS
• Milestones for large muscle activities
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Development of posture
Learning to walk
First year milestones - walks easily
Development in second year
• Skilled and mobile: pull toys, climb stairs
• Natural exercise: walk quickly, run stiffly
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FIGURE 5.16 - MILESTONES IN GROSS
MOTOR DEVELOPMENT
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FINE MOTOR SKILLS
• Motor skills that involve finely tuned
movements
• Finely tuned (coordinated) movements
• Perceptual-motor coupling necessary
• Finger dexterity (thumb and forefinger)
• Two types of grasps: Palmar and Pincer
• Wrists and hands turn and rotate more
• Experience and exercise have impact
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SENSATION AND PERCEPTION
• Sensation: Stimulation of the sense organs.
• Perception: Interpretation of that stimulation.
• Process of integrating disjointed sensations into meaningful
patterns through perception
• Measuring Sensation/Perception
• Habituation/Dishabituation
• Head movement indicates some vision
• Visual preference method: Measuring the length of time
they attend to different stimuli
• Tracking - Applied to vision and hearing
• Technology
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VISION
• Visual acuity at Birth
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Estimate of 20/600
Best see objects 7 to 9 inches from eyes
Greatest gains in visual acuity between birth and 6 months
By about 3 to 5 years of age, approximate adult levels
• Neonates have poor peripheral vision
• 30 degree angle; By 7 weeks increases to 45 degrees; By 6
months of age, equal to adult (90 degrees)
• Able to track movement within one day of birth
• Preference for moving objects
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VISION
• Visual accommodation
• Self-adjustments made by eye lens to bring objects into focus
• Neonates show little or no visual accommodation
• Focus on objects 7 to 9 inches away
• Convergence
• Does not occur until 7 or 8 weeks
• Color perception
• At birth, cones are less well developed than rods
• Fully mature around 3 months (Distinguish between blue/green)
• By 4 months can distinguish between similar colors/hues
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CONVERGENCE OF THE EYES
Figure 4.5
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THE LOOKING CHAMBER
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VISUAL PREFERENCES
• Preferences
• Moderately complex
• Movement
• Contour
• Infants prefer faces
• Discriminate maternal and stranger faces
• Prefer attractive faces
• Pay most attention to edges
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Preferences for Visual Stimuli in
2-Month-Olds
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MOVEMENTS OF 1- AND 2-MONTH-OLDS
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DEPTH PERCEPTION
• Depth Perception
• Develops around 6 months (onset of crawling)
• Research using the Visual Cliff
• Gibson and Walk (1960)
• Heart-rate response to determine fear
• Relationship between crawling and fear of heights
• Avoidance of the cliff and infants’ posture
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HEARING
• Fetuses respond to sound
• Can localize sound
• Startled by loud noises
• Neonates respond to amplitude and pitch
• Show preference for mothers’ voices
• Responsive to sounds and rhythms of speech
• Capable of perceiving phonemes of other languages
• Show no preference for specific languages
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HEARING
• DeCasper & Spence (1986)
• Newborns can remember and prefer a story read by
mom during the last 6 weeks of pregnancy.
• Exposed to 3 ½ hours of story.
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DEVELOPMENT OF HEARING
• By 1 month, infants perceive differences between similar
speech sounds
• By 3½ months discriminate caregivers’ voices
• Infants perceive most speech sounds present in world
languages
• By 10 to 12 months, lose capacity to discriminate sounds
not found in native language
• By 6 months, they can detect high frequency sounds nearly as
well as preschoolers.
• By 6 months, they can appreciate distance.
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SMELL AND TASTE
• Smell
• Well-developed at birth
• Demonstrate aversion for noxious and preference for pleasant
odors
• Vanilla and Strawberry
• Recognize familiar odors
• Recognize mom by 6 days
• Taste
• Sensitive to different tastes
• Demonstrate facial expressions in response to tastes
• Prefer sweet tastes
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FACIAL EXPRESSIONS ELICITED BY
SWEET, SOUR, AND BITTER SOLUTIONS
TOUCH AND PAIN
• Touch
• Sensitive to touch
• Touch elicits many reflex behaviors
• Pain
• Past belief that neonates are not sensitive to pain
• Neonates not cognitively equipped to ruminate about pain
• Conditionable – distress when confronted with situation
that previously presented itself as painful
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