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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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