WHAT WILL YOU KNOW?

What part of an infant grows most in the first two years?

Does brain wiring in the first two years depend on genes or experience?

Which of the five senses develops last: seeing, hearing, tasting, touching, or smelling?

What happens if a baby does not get his or her vaccinations?

Body Changes

Body sizeBirthweight doubles by month four and triples by 1 year

Average weight at birth: 7 pounds

Average length: 20 inches

Birth catch-upSmall babies experience extra gain to catch up to the norm.

Body Changes

NormsDefined standards of typical performance by which a child's development in a variety of domains can be measured

These numbers are norms or average measurements; individuals vary.

PercentileNumber that indicates rank compared to other similar people of the same age

Percentiles range from zero to 100.

Weight by Gender: Birth to 24 Months

Eat and Sleep The rate of increasing weight in the first weeks of life makes it obvious why new babies need to be fed, day and night.

Same Boy, Much ChangedAll three photos show Conor, first at 3 months, then at 12 months, and finally at 24 months. Note the rapid growth in the first two years, especially apparent in the changing proportions of the head, compared to the body and use of the legs.

Sleep

Sleep specifics vary because of biology and the social environment.Newborns sleep about 15-17 hours a day, in one- to three-hour segments.

Newborns' sleep is primarily active sleep.

Newborns have a high proportion of REM (rapid eye movement) sleep.

Cultural difference are apparent in sleep patterns.

More Sleep Information

Over first months, relative amount of sleep time changes.

Infants vary in how long they sleep at one time.

Over the early weeks, transitional sleep declines and slow-wave sleep increases.

Caregiver response to infant behavior during sleep hours also impacts sleep patterns.

Co-Sleeping

Asian and African mothers worry more about separation; European and North American mothers worry more about privacy and sex.

Pros• Easier response time• Less parental exhaustion• More convenient for breast-

feeding

Cons• Higher SIDS• Ghosts in the nursery

phenomenon

Infant at Risk? Sleeping in the parents’ bed is a risk factor for SIDS in the U.S., but don’t worry about this Japanese girl. In Japan, 97 percent of infants sleep next to their parents, yet infant mortality is only 3 percent per 1,000-compared with 7 per 1,000 in the U.S. In this bed, or this mother, or this sleeping position protective?

Connections in the Brain

Neuron

One of billions of nerve cells in the central nervous system (CNS)

Communication within CNS begins with neurons.

Most neurons are created before birth, at a peak production rate of 250,000 new cells per minute in mid-pregnancy (Purves et al., 2004).

In infancy, the human brain has billions of neurons.

Brain Development

Brain stem• Region deep

inside brain which control automatic responses

Midbrain• Area of brain

that affects emotions and memory

Cortex• Outer layers

of the brain where most thinking, feeling, and sensing occurs.

Prefrontal cortex• Area of the

cortex at the very front of the brain that specializes in anticipation, planning, and impulse control.

Brain Development: Dendrites Sprouting

Axon• Fiber that

extends from a neuron and transmits electrochemical impulses from that neuron to the dendrites of other neurons.

Dendrite• Fiber that

extends from a neuron and receives electrochemical impulses transmitted from other neurons via their axons.

Synapse• Intersection

between the axon of one neuron and the dendrites of other neurons.

Neurotransmitter• Brain chemical

that carries information from the axon of a sending neuron to the dendrites of a receiving neuron.

How Two Neurons CommunicateThe infant brain contains billions of neurons, each with one axon and many dendrites.

Every electrochemical message to or from the brain causes thousands of neurons to fire, each synapse to neighboring neurons.

This electron micrograph shows neurons greatly magnified, with their tangled but highly organized and well-coordinated sets of dendrites and axons.

Brain Development

Exuberance and pruningSpecifics of brain structure and growth depend on genes and maturation, but even more on experience.

Expansion and pruning of dendrites occur for every aspect of early experience.

Unused dendrites whither postnatally to allow space between neurons in the brain, allowing more synapses and thus more complex thinking.

Synapse Formation and Dendrite Formation

Experience Shapes the Brain

Necessary and possible experiences (Greenough and colleagues)Experience-expectant brain function

Experience-dependent brain function

Experience Shapes the Brain

Examples from twin studies

Until about 10 months, experience-expectant circumstances not influenced by SES

After 10 months, genetics vary more than context in high-SES families

Examples from bird brains

Birds inherit genes that produce the brain cells they need to learning new songs or find hidden seeds

For the dendrites and neurons to connect, birds depend on specific experiences with song-learning or seed-finding

Face Recognition

Fusiform face area of brain

Makes newborn infant adept at face recognition

Experiences

Refine face perception and trigger immediate recognition

Own-race effect

Apparent before first birthday and persists throughout life

Iona Is Not Flora If you heard that Dariowas quite different from Louis or Boris, would you stare at unfamiliar monkey

faces more closely in the future?For 6-month-olds, the answer is yes

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Harming the Infant Brain

Lack of stimulation• Playing, allowing varied

sensations, and encouraging movement necessary for brain connections

Stress and the brain• Overabundance of stress

hormones damages later brain functioning

Severe social deprivation• Anecdotal evidence with

human children and research with other mammals confirms that isolation and sensory deprivation harm the developing brain.

Intervention• Shaken baby syndrome is a

life-threatening injury that occurs when an infant is forcefully shaken back and forth. This motion ruptures blood vessels in the brain and breaks neural connections.

Harming the Infant Brain

Shaken baby syndromeIs considered an abusive head trauma

Is a life-threatening injury

Occurs when an infant is forcefully shaken back and forth

Results in motion that ruptures blood vessels in the brain and breaks neural connections

Is not always the reason brain injury occurs; may lead to false accusations

Sensation and Movement: The Senses

Sensory developmentTypically precedes intellectual and motor development

SensationResponse of a sensory system (eyes, ears, skin, tongue, nose) when it detects a stimulus

PerceptionMental processing of sensory information when the brain interprets a sensation

Perceiving and Moving: The Senses

Perception follows sensation.Infants' brains are especially attuned to their own repeated social experiences and perception occurs.

Infant brain and auditory capacity to hear sounds in the usual speech range.

The parts of the cortex dedicated to the senses develop rapidly.

Moving and Perceiving: Hearing and Seeing

Hearing• Develops during the last

trimester of pregnancy• Most advanced of the

newborn's senses• Speech perception by 4

months after birth

Moving and Perceiving: Hearing and Seeing

SeeingLeast mature sense at birth

Newborns focus between 4 and 30 inches away

Experience and maturation of visual cortex improve shape recognition, visual scanning, and details.

Binocular vision at 3 months

Moving and Perceiving: Smelling and Tasting

Smell and taste Function at birth

Rapidly adapt to the social world

Related to family and cultural preferences

May have evolutionary function

Moving and Perceiving: Touch and Pain

Touch

Sense of touch is acute in infants.

Although all newborns respond to being securely held, soon they prefer specific, touches.

Pain and temperaturePain and temperature are often connected to touch.

Some people assume that even the fetus can feel pain.

Others say that the sense of pain does not mature until months or years later.

Motor Skills: Gross Motor Skills

Motor skillsLearned abilities to move some part of the body, in actions ranging from a large leap to a flicker of the eyelid

Course of developmentCephalocaudal (head-down) and proximodistal (center-out) direction

Motor Skills: Gross Motor Skills

Gross motor skills• Physical abilities involving

large body movements, such as walking and jumping

Young Expert This infant is an adept crawler. Note the

knees as well as the arm and leg strength needed to support the body in this early

version of push-ups.

Dynamic Systems Underlying Motor Skills

Three interacting elements underlying motor skills

• Muscle strength• Brain maturation• Practice

Motor Skills: Fine Motor Skills

Fine motor skillsPhysical abilities involving small body movements, especially of the hands and fingers, such as drawing and picking up a coin

Shaped by culture and opportunity

Moving and Perceiving: Dynamic Sensory Systems

Most important experiences are perceived with interacting senses in dynamic systems.Sensations facilitate social interaction and comfort.

By 6 months, infant are able to coordinate the senses.

Dynamic Sensory-Motor Systems

The entire package of sensations and motor skills furthers three goals.

•Social interaction

•Comfort

•Learning

SuccessAt 6 months, this baby is finally able to grab her toes. From a developmental perspective, this achievement is as significant as walking, as it requires coordination of feet and fingers. Note her expression of determination and concentration.

Motor Skills: Cultural Variations

All healthy infants develop skills in the same sequence, but the age of acquisition varies.Variations influences• Genes• Cultural patterns• Nutrition• Caregiving patterns

Surviving in Good Health

Statistics

8 billion children were born between 1950 and 2015; almost a billion of them died before age 5.

World death rate in the first five years of life has dropped about 2 percent per year since 1990.

• Improvement in clean water, nourishing food, immunization, medical treatments

Well Protected

Disease and early death are common in Africa, where this photo was taken, but neither is likely for 2-year-old Salem.

Scientists At Work: SIDS

In her research with young children, Beal found that almost all SIDS babies she studied were sleeping on their stomachs.

Stomach sleeping is a proven, replicated risk.

Other risks include low birthweight, being male, smoking parents, soft blankets and pillows, bed-sharing, winter, and a variety of abnormalities.

Most SIDS victims experience several risks.

Surviving in Good Health

ImmunizationPrimes the body's immune system to resist a particular disease

Contributes to reduced mortality and population growth; herd immunity

Successes• Smallpox• Polio• Measles• Rotavirus

Surviving in Good Health

Immunizations are unsafe for:Embryos exposed to rubella

Newborns

People with compromised immune systems

ProblemsNo effective vaccine found for AIDS, malaria, cholera, typhoid, and shigellosis

Many rural areas of world not reached

Parental concerns about link between autism and immunizations

Surviving in Good Health: Nutrition

Adequate nutritionFor every infant disease (including SIDS), breast-feeding reduces risk and malnutrition increases it, stunting growth of body and brain.

Breastfed babies are less likely to develop allergies, asthma, obesity, and heart disease.

As the infant gets older, the composition of breast milk adjusts to the baby's changing nutritional needs.

National Trends in Breast-Feeding Rates

Surviving in Good Health

Malnutrition

Protein-calorie malnutrition• Condition in which a person does not consume sufficient food of

any kind that can result in several illnesses, severe weight loss, and even death

Stunting• Failure of children to grow to a normal height for their age due to

severe and chronic malnutrition

Wasting• Tendency for children to be severely underweight for their age as a

result of malnutrition

Stunting

Genetic? The data show that basic nutrition is still unavailable to many children in the developing world.

Effects of Chronic Malnutrition

Brains may not develop normally.

Protection against common diseases may be reduced.

Some diseases result directly from malnutrition

• Marasmus • Kwashiorkor

Infant malnutrition is common in nations at war (like Afghanistan, bottom)

or with crop failure (like Niger, top).

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