PSYC 2314
Lifespan Development
Chapter 5
The First Two Years:
Biosocial Development
Physical Growth and Health
• The average North American newborn measures
about 20 inches and weighs about 7 lbs.
• By age 1, body weight has tripled to an average 22
lbs; body length has increased to almost 30 inches.
• Growth slows during the second year. By age 2,
body weight averages 30 lbs, nearly 1/5 of adult
weight; body length ranges from 32-36 inches or
½ of adult height.
SIDS
• Caused by an unsteady breathing reflex,
usually between 2-4 months.
• Preventive measures:
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Removing soft bedding
Eliminating second-hand smoke
Prolonging breast feeding
Laying babies down to sleep on their backs, not
stomachs
Survival Rates
• Survival in the early years of life has
increased from a century ago, primarily
because of immunization. Among the
diseases that have either been completely
eradicated, or nearly so, are smallpox, polio,
whooping cough, diphtheria, and measles.
Brain Growth and Development
• Transient exuberance—the phenomenal
increase in neural connections over the first
2 years.
– Neurons: axon, dendrites, synapses, myelin
sheaths
Brain Growth and Development
• As the nervous system matures, the axons become
coated with myelin, allowing children to gain
increasing control over their motor functions and
sensory abilities, which facilitates their intellectual
functioning.
• The myelination process proceeds most rapidly
from birth to age 4 (but continues through
adolescence).
Brain Growth and Development
• The frontal cortex, which assist in selfcontrol and self-regulation, is immature in
the newborn. As frontal neurons become
myelinated and interconnected during the
first year, babies become better able to
regulate their reflexes and sleep-wake
patterns. Cognitive abilities requiring
deliberation and emotional self-control also
emerge.
Brain Maturation
• Caressing a newborn, talking to a preverbal infant,
and showing affection toward a small person too
immature to love in return may be essential first
steps toward developing that person’s full human
potential.
• Loving and stimulating experiences should occur
throughout life. The brain retains some
plasticity—that is, some capacity for developing
new pathways—as long as experience continues.
Motor Skills
• Developmental biodynamics: the study of
the maturation of movement skills.
• Reflexes: the newborn’s first motor
abilities
– Breathing
– Sucking
– Rooting
Motor Skills
• Gross motor skills: physical skills
involving large body movements such as
waving the arms, walking, and jumping.
• Fine motor skills: skills that involve small
body movements (usually of the hands and
fingers).
Motor Skills
• Between 8-10 months, most infants are
crawling on “all fours.”
• Average child can walk with assistance at 9
months, stand alone momentarily at 10
months, and walk well unassisted at 12
months.
• By 6 months, most babies can reach, grab,
and hold onto objects.
Motor Skills
• Norms reflect the average age at which
certain skills are acquired. Norms vary
from place to place and group to group.
• Variation in norms can be attributed
primarily to inherited factors, such as
activity level, rate of physical maturation,
and body type. Patterns of infant care may
also be influential.
Sensory and Perceptual Capacities
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Sensation: detection of a stimulus
Perception: making sense of the stimulus
Vision: least developed of the senses
Hearing: Acute at birth. Can distinguish
their mother’s voice from the voices of
other women.
Sensory and Perceptual Capacities
• About 1 in every 1,000 infants is
profoundly deaf.
• A common cause of temporary hearing loss
during infancy is middle ear infection, also
known as otitis media.
Sensory and Perceptual Capacities
• When this condition becomes chronic, the
inner ear fills with fluid, and hearing may
be impaired for weeks or months.
• Chronic otitis media may slow learning
ability, the ability to make friends, the
ability to deflect aggression, and social
problems solving.
Sensory and Perceptual Capacities
• Treatments for otitis media include
antibiotics and the placement of a tube to
drain fluid from the inner ear.
Sensory and Perceptual Capacities
• At birth, infants can discriminate all the
basic tastes except salty.
• Sense of smell is even more acute.
• Sense of touch also develops rapidly.
• Sense of motion is strong at birth.
Nutrition
• Breast milk is the ideal food for most babies.
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Sterile and body temperature
Contains more essential vitamins and iron
More digestible
Provides the infant with immunity to any disease the
mother has already had or been inoculated against
– Decreases the frequency of almost every other common
infant ailment
• By 4-6 months, cereals and fruits should be added
to the ideal diet.
Nutrition
• Protein-calorie malnutrition: when a child
does not consume sufficient nourishment
– Marasmus: a condition in which growth stops,
body tissues waste away, and the infant
eventually dies.
– Kwashiorkor: a condition caused by a
deficiency of protein in which the child’s face,
legs, and abdomen swell with water.
Nutrition
• Primary cause of malnutrition in developing
countries is early cessation of breastfeeding and
the substitution of infant formulas that are often
contaminated or improperly prepared.
• Undernutrition is caused by a complex interaction
of factors, with political and familial problems
being prime underlying factors.
Nutrition
• Long-lasting malnutrition in infancy can
cause intellectual as well as physical
deficits.
• The consequences of undernutrition in
infancy are more variable, depending on its
duration and on the intellectual stimulation
of the environment after infancy.
Nutrition
• Preventing undernutrition:
– Provide supplements, nearby and nourishing,
for all children
– Improve maternal education so that every
mother will participate