PSY100H1 Chapter 11: Human Development
2 Aug 2010
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CHAPTER ELEVEN: HUMAN DEVELOPMENT
! Developmental psychology is concerned with changes in physiology, cognition and social behaviour over the life
span
! the mind develops in ways that are adaptive, as new useful skills appear at appropriate times, even in the
absence of specific training
! every person’s life is touched by the lives of others
! infants innately form bonds with others, an adaptive trait that provides protection and facilitates survival
! as children grow, they learn how to communicate with and behave appropriately around others and how to
establish and maintain relationships
What Shapes a Child?
! Human development follows a predictable progression
! during the prenatal period, the body develops in a fixed sequence, ultimately turning into a male or female infant
based on genetic instructions
! all human babies make eye contact quickly after birth
" display their first social smile at around six weeks
" learn to roll over, sit up, crawl, stand, walk and talk (in that order)
! the consistency of this pattern suggests that our genes set the pace and order of development
! however, the environment also influences what happens throughout the development process
" ie, children raised in different cultures often achieve developmental milestones at a different pace
# healthy children in Uganda walk by 10 months, children in France do not walk for 15 months
! difference are due in part to different patterns of infant care across cultures
! genes and experience depend on and affect one another
! without an environment to trigger gene expression, a human does not develop into a fully functioning member of
human society
Development Starts in the Womb
! first two months, developing human is known as an embryo
" internal organs such as heart, lungs, liver, kidneys, sex organs and nervous system begins to form
! after two months, called a fetus
" undergoes a great deal of physical growth as the whole body takes its infant form
! the final trimester puts the finishing touches on the human
" if healthy, capable of survival outside the womb
Physical Development
! genes govern much of the prenatal development of the human nervous system
! most of the brain’s nerve cells develop in a specific sequence in the first 7 months of gestation
! week 4: the forebrain, midbrain and hindbrain begin to form
! week 7: the cells that will form the cortex are visible
! week 10: the thalamus and hypothalamus are visible
! week 12: the basal ganglia and the left and right hemispheres
! 7th month: fetus has a working nervous system
! birth: the brain is complex, it has cortical layers, neuronal connectivity and myelination
! the brain continues to develop throughout childhood into adulthood
! hormones that circulate in the womb influence the developing fetus
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" if the mother’s thyroid does not produce sufficient levels of thyroid hormones, the fetus is at risk for lower
IQ and diminished intellectual development
! the mother’s emotional state can also affect the developing fetus
! the level of testosterone in the womb are correlated with a range of behaviours later in childhood, from making
eye contact to developing vocabulary
! speculate that maternal hormones may play an important role in autism, a communication and cognitive disorder
Teratogens
! environmental influences may have adverse effects on the developing fetus
! drugs, alcohol and illness can all impair physical and cognitive development $ teratogens
! teratogens are agents (bacteria, viruses, chemicals and drugs) that can cause abnormal development in the
womb
! the extent to which a teratogen causes damage depends on when the fetus is exposed to it, as well as the length
and amount of exposure
" exposure to a teratogen at about 4 weeks of age can interfere with the proper development of the brain
! ie, excessive consumption of alcohol during pregnancy can lead to fetal alcohol syndrome, the symptoms include
low birth weight, face and head abnormalities, slight mental retardation and behavioural and cognitive problems
" even small amounts of alcohol can be problematic
! ie, smoking cigarettes during pregnancy can lead to low birth weight, spontaneous abortion or birth defects
! physical effects of exposure to certain teratogens may be obvious at birth, but language or reasoning disorders
may not become apparent until the child is older
Brain Development Promotes Learning
! newborns come into the world able to see, smell, hear, taste and respond to touch
! these skills are not fully developed at birth but the newborn is capable of processing some sensory stimuli
! young infants also have a reasonably acute sense of smell
" ie, in studies infants turned their heads toward a pad containing their own mother’s milk but not toward pads
containing milk from other breast-feeding mothers
! sense of hearing in young infants is quite good too
" ie, infants are startled by loud sounds and often will turn their bodies toward the source of sound
" sense of hearing is must greater than their sense of vision
! infants’ sense of vision is quite limited
" the range of their visual acuity is 8-12 inches
" may be adaptive, since it encourages the infant to focus on what is most important (mother’s face & breast)
and promotes the beginnings of social interaction for the child
# perceptual skills of newborns increase tremendously over the first few months of life
! newborns have a variety of basic reflexes that aid survival
! an innate reflex is the rooting reflex, the automatic turning and sucking that infants engage in when a nipple or
similar object is near their mouths
! some believe that these reflexes pave the way for learning more complicated behaviour patterns such as feeding
oneself or walking
! the brain is sufficiently developed at birth to support basic reflexes, but it appears that further brain
development is necessary for cognitive development to occur
! early brain growth has 2 components
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1. specific areas within the brain mature and become functional
2. regions of the brain learn to communicate with each other through synaptic connections
! one important way that brain circuits mature is through myelination, the brain’s way of insulating its “wires”
(Chapter 3)
" begins on the spinal cord during the first trimester and on the brain’s neurons during the second trimester
" fibers are wrapped with a fatty sheath to increase the speed with which they are able to transmit signals
" occurs in different brain regions at different stages of development and is believed to reflect the maturation
of the fibers
" hearing and balance areas are fully myelinated at birth
" areas involved in abstract thinking do not become fully myelinated until after age 20
! the myelinated axons form synapses with other neurons
! the infant brain grows far more of these connections than it will ever use
! then the brain adopts a very strict “use it or lose it” policy
" connections that are frequently used are preserved; those that are not, decay and disappear
" process is called synaptic pruning and it occurs in different areas of the brain at different times
! once connections are established, the brain sets about making them more permanent
" ie, through increasing myelination
! some developmental psychologists believe that not until certain brain connections are made do infants develop
specific cognitive skills
! the brain is also a highly plastic organ
" part of its hard wiring includes the ability to adapt to different environments
! the brain’s physical development continues through the growth of neurons and the new connections they make
" the brain grows from about 350 grams to about 1250 grams (about 80% of the adult size) by age 4
" size increase is due to myelination and to new synaptic connections among neurons
! children who are malnourished not only have less myelination, but might also lack the energy to interact with
objects and people in their environments
" lack of stimulation also undermines brain development
! although genes provide instructions for the maturing brain, how the brain changes during infancy and early
childhood is also very much affected by the environment
" both nature and nurture matter in how the physical brain grows
Critical Learning Periods
! a critical period is a development stage during which young animals are able to acquire specific skills and
knowledge
" if these skills and knowledge are not acquired during the critical period, they cannot be acquired at a later
point in development
! the key to learning is creating connections among certain neurons, and that critical learning periods may exist
because brain development goes through periods during which certain connections are most easily made,
assuming the right stimulus is provided
! there are biologically determined time periods when a child must be exposed to language in order to achieve
normal brain development
" termed the critical period hypothesis by Eric Lenneberg
# theory states that the environmental input is important, but biology determines when an organism needs
to receive particular input in order to make use of it
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Document Summary
every person"s life is touched by the lives of others infants innately form bonds with others, an adaptive trait that provides protection and facilitates survival. as children grow, they learn how to communicate with and behave appropriately around others and how to establish and maintain relationships. during the prenatal period, the body develops in a fixed sequence, ultimately turning into a male or female infant based on genetic instructions. all human babies make eye contact quickly after birth. however, the environment also influences what happens throughout the development process ie, children raised in different cultures often achieve developmental milestones at a different pace. healthy children in uganda walk by 10 months, children in france do not walk for 15 months. difference are due in part to different patterns of infant care across cultures. genes and experience depend on and affect one another.
