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 size
Birthweight doubles by month four and triples by 1
year
Average weight at birth: 7 pounds
Average length: 20 inches
Birth catch-up
Small babies experience extra gain to catch up to
the norm.
Body Changes
Norms
Defined 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.
Percentile
Number 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 Changed
All 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 oneto 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 breastfeeding
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
Midbrain
Cortex
• Region deep
inside brain
which control
automatic
responses
• Area of brain
that affects
emotions and
memory
• 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
electrochemic
al impulses
from that
neuron to the
dendrites of
other neurons.
Dendrite
• Fiber that
extends from
a neuron and
receives
electrochemic
al 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
Communicate
The 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 wellcoordinated sets of dendrites
and axons.
Brain Development
Exuberance and pruning
Specifics 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
Examples from bird
brains
Until about 10 months,
experience-expectant
circumstances not
influenced by SES
Birds inherit genes that
produce the brain cells they
need to learning new songs
or find hidden seeds
After 10 months, genetics
vary more than context in
high-SES families
For the dendrites and
neurons to connect, birds
depend on specific
experiences with songlearning or seed-finding
REPRINTED FROM SCOTT, LISA S. & MONESSON, ALEXANDRA. (2010). EXPERIENCE-DEPENDENT NEURAL
SPECIALIZATION DURING INFANCY. NEUROPSYCHOLOGIA, 48 (6), 1857-1861. DOI: 10.1016/J.NEUROPSYCHOLOGIA.
2010.02.008. COPYRIGHT 2010 WITH PERMISSION FROM ELSEVIER
Iona Is Not Flora If you heard that Dario
was 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
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
Harming the Infant Brain
Lack of stimulation
Intervention
• Playing, allowing varied
sensations, and encouraging
movement necessary for brain
connections
• 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.
Stress and the brain
Severe social deprivation
• Overabundance of stress
hormones damages later brain
functioning
• Anecdotal evidence with
human children and research
with other mammals confirms
that isolation and sensory
deprivation harm the
developing brain.
Harming the Infant Brain
Shaken baby syndrome
Is 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 development
Typically precedes intellectual and motor
development
Sensation
Response of a sensory system (eyes, ears, skin,
tongue, nose) when it detects a stimulus
Perception
Mental 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
Seeing
Least 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 temperature
Pain 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 skills
Learned abilities to move some part of the body, in
actions ranging from a large leap to a flicker of the
eyelid
Course of development
Cephalocaudal (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 skills
Physical 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 SensoryMotor Systems
The entire package of
sensations and motor
skills furthers three
goals.
•Social interaction
•Comfort
•Learning
Success
At 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, bedsharing, winter, and a variety of abnormalities.
Most SIDS victims experience several risks.
Surviving in Good Health
Immunization
Primes 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
Problems
No 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 nutrition
For every infant disease (including SIDS), breastfeeding 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.
AP PHOTO/SCHALK VAN ZUYDAM
Effects of Chronic
Malnutrition
Brains may not develop
normally.
©DANG NGO/ZUMAPRESS.COM
Protection against common
diseases may be reduced.
Infant malnutrition is common in nations at
war (like Afghanistan, bottom)
or with crop failure (like Niger, top).
Some diseases result
directly from malnutrition
• Marasmus
• Kwashiorkor