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Chapter 3

FRHD 1010 Chapter 3: FRHD 1010 - Chapter 3 Notes


Department
Family Relations and Human Development
Course Code
FRHD 1010
Professor
Susan Chuang
Chapter
3

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Chapter 3: The First Two Years Body and Mind
Growing in Infancy
o In infancy, growth is so rapid and the consequences of neglect are so severe that gains
are closely monitored
Body Size
o Weight gain is dramatic
o Newborns lose a bit of weight in the first three days of life and then gain about 30 grams
a day for several months
o Birth weight typically doubles by 4 months and triples by a year
o Physical growth in the second year is slower but still rapid
o Two year olds are half their adult height and about a fifth of their adult weigh, four times
heavier than they were at birth
o Each of these numbers is a norm, which is an average or standard for a particular
population
o At each well-baby checkup, a doctor measures the baby’s growth and compares it to that
baby’s previous numbers
o Abnormal growth may signify a problem, which is why early check-ups are vital
o Prenatal and postnatal brain growth is crucial for later cognition
o If teething or a stuffed nose slow weight gain, nature protects the brain, a phenomenon
called head-sparing
o From two weeks after conception to 2 years, the brain grows more rapidly than any other
part of the body
Brain Development
o The brain contains neurons, axons, dendrites, neurotransmitters, synapses, and the
cortex, and the prefrontal cortex
o Communication within the central nervous system (CNS) the brain and spinal cord
begins with nerve cells, called neurons
o The brain has billions of neurons, most of them (70%) in the cortex
o The final part of the brain to mature is the prefrontal cortex, the area for anticipation,
planning and impulse control
o Neurons are linked to other neurons by intricate networks of nerve fibres called axons
and dendrites
o Each neuron has a single axon and numerous dendrites, which spread out like branches
on a tree
o The axon of one neuron meets the dendrites of other neurons at intersections called
synapses, tiny gaps that are critical communication links within the brain
o Axon and dendrites do not touch at synapses
o Neurons communicate by sending electrochemical impulses, called neurotransmitters
through their axons to synapses, to be picked up by the dendrites of other neurons
o An estimated fivefold increase in dendrites in the cortex occurs in the 24 months after
birth, with about 100 trillion synapses being present at age 2
o Early dendrite growth is called transient exuberance: exuberant because it is so rapid
and transient because some of it is temporary

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o The expansive growth of dendrites is following by pruning
o Some dendrites wither away because they are never used no experiences have caused
them to send a message to other neurons
o During the prenatal stage, the brain develops rapidly, as various parts take on their
specialized function
o The brain is high in plasticity, meaning that it can be modified and changed by
environmental circumstances
o One advantage of the brain’s plasticity is the ability to compensate or take over the
functions of certain areas that may have been damaged by disease or accident ]
o Plasticity also means the brain is highly vulnerable to impoverished or restricted
environments, and this can lead to damage that has significant effects
o Because of brain plasticity and its consistent development, parents and others in the
infants’ social world play an important role in the baby’s brain development
o The brain is not yet under thoughtful control, since the prefrontal cortex is not well
developed
o If frustrated caregiver reacts to crying by shaking the baby, it can cause a life-threatening
condition called shaken baby syndrome (SBS), which occurs when infants are shaken
back and forth sharply and quickly
o Self-righting, an inborn drive to remedy deficits is built into the human system
o Human brains are designed to grow and adapt; plasticity is apparent from the beginning
of life
Sleep
o One consequence of brain maturation is the ability to sleep through the nigh
o Normally, newborns sleep 15-17 hours a day, in one-to-three hour segments
o Sleep specifics vary not only because of biology (age and genes), but also because of the
social environment
o Full-term newborns dream a lot, about half their sleep is REM (rapid eye movement)
sleep, with flickering eyes and rapid brain waves
Perceiving and Moving
o Developmentalists have traced the immediate and rapid development of every skill of
infants
The Senses
o Newborns have open eyes, sensitive ears, and responsive noises, tongues and skin
o Sensation precedes perception, and perception leads to cognition
o In order to learn, babies need to begin by responding to every sensation that might be
significant
o Sensation occurs when a sensory system detects a stimulus, as when the inner ear
reverberates with sound or the retina or pupil of the eye intercept light
o Sensation begin when an outer organ (eye, ear, nose, tongue, skin) meets anything that
can be seen, heard, smelled, tasted or touched
o Perception occurs when the brain notices and processes a sensation
o This happens in the cortex, usually as the result of a message from one of the sensing
organs

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o Infants’ brains are especially attuned to their own repeated social experiences, and that is
how perception occurs
o The sense of touch is acute in infants, with wrapping, rubbing and cradling all soothing to
many new babies
o Pain is not one of the five senses, but it is often connected to touch
For example, some babies cry when being changed because sudden coldness on
their skin is distressing
o The sense of hearing develops during the last trimester of pregnancy, which means that
fetuses hear sounds in the womb
o Vision is the least mature sense at birth
o Almost immediately, experience combines with maturation of the visual cortex to improve
the ability to see shapes and then notice details
o Because binocular vision (coordinating both eyes to see one image) is impossible in the
womb, many newborns seem to use their two eyes independently
o Through the amniotic fluids, infants develop their senses of taste and smell while still in
the womb
Motor Skills
o The most dramatic motor skills (any movement ability) is independent walking
o Reflexes become skills if they are practised and encouraged
o Deliberate actions that coordinate many parts of the body, producing large movements,
are called gross motor skills
o Infants control their heads, lifting them up to look around then they control their upper
bodies; their arms and finally their legs and fee t
o The dynamic systems underlying motor skills have three interacting elements:
1. Muscle strength. Newborns with skinny legs and 3-months-olds buoyed by
water making stepping movement, but 6-month-olds on dry land do not; their
legs are too chubby for their underdeveloped muscles
2. Brain maturation. The first leg movements kicking occur without much
thought, as the brain matures deliberate leg action becomes possible
3. Practice. Unbalance, wide-legged, short strides become a steady, smooth gait
o Muscle strength, may explain why newborns’ innate stepping reflexes disappear
o As infants gain weight, they dramatically increase their leg mass, which alters the
dynamics of their moving limbs
o Practice is powerfully affected by caregiving before the first independent step
o Once toddlers can walk themselves, at around 1, they practise obsessively
o Small body movements are called fine motor skills
o Finger movements are fine motor skills, enabling humans to write, draw, type, tie, etc.
o Toward the end of the first year and throughout the second, finger skills improve, as babies
master the pincer movement (using thumb and forefinger to pick up tiny objects) and
self-feeding (first with hands, then fingers, then utensils)
Dynamic Sensory-Motor Systems
o The entire package of sensations and motor skills furthers three goals:
1. Social interaction
2. Comfort
3. Learning
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