Ch.12 Notes.doc

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18 Mar 2012

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Ch.12 Lifespan Development
-prenatal period: the 9 months b/w conception and birth. This period is divided
into 3 developmental stages: the zygotic, the embryonic, and fetal.
Stages of Prenatal Development
- union of ovum (egg) and sperm is conception – starting pt for prenatal development
-zygote stage: first stage of prenatal development, during which zygote divides
many times and internal organs begin to form (2 weeks)
- this single cell divides many times and internal organs begin to form
- first week = 100 cells/one layer for skin, hair, nervous system and sensory organs
and another for digestive and respiratory systems and glands
- third layer of cells will eventually develop into muscles and circulatory and
excretory systems
-embryonic stage: second stage of prenatal development, beginning 2 weeks and
ending about eight weeks after conception, during which heart begins to beat, brain
starts to function, and most major body structures begin to form
- end of this stage – arms, hands, fingers, legs, toes, shoulders, head and eyes are
-teratogens: substances, agents and events that cause birth defects
- embryo is most susceptible to these chemicals during this stage
- beginning of sexual development occurs during embryonic stage
- 23rd chromosome determines sex – female contributes X, whereas male contributes
X or Y
- Male (XY), Female (XX)
-Androgens: primary class of sex hormones in males. Most important androgen is
testosterone – they bring about development of male internal sex organs, penis and
- Development of female sex organs – ovaries, uterus, vagina and labia occur
naturally – does not need to be stimulated by hormone
-Fetal stage: 3rd and 4th stage of prenatal development, which lasts for about 7
months, beginning with appearance of bone tissue and ending with birth
Threats to Normal Prenatal Development
- most important is mother’s diet – fetus’s only source of nutrition
- if mother is malnourished, fetus’s nervous system develops abnormally and
intellectual deficits may result
- certain antibiotics especially in large quantities over long periods can produce fetal
defects (i.e. tetracycline can cause irregularities in bones and discolouration of teeth
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- also cigarette smoking – carbon monoxide in cigarette smoke reduces supply of
oxygen to fetus
- reduced oxygen levels are particularly harmful to fetus during last half of
pregnancy when fetus is developing most rapidly
- can increase miscarriages, low-birth weight, increase chance of premature birth and
Caesarean section
- mothers using cocaine during pregnancy – low-birth weight, premature birth,
smaller than normal head circumference, also interferes with neural development
- alcohol – pre and postnatal growth deficits, deformation of eyes and mouth, low
brain mass, heart deformation - fetal alcohol syndrome (intellectual development
falls short of other children
Motor Development
- baby’s reflexes – sucking, rooting, and swallowing are most important responses
-maturation: any relatively stable change in thought, behaviour, or physical growth
that is due to aging process and not to experience
- development of motor skills requires 2 ingredients: maturation of child’s nervous
system and practice
- physical development of nervous system depends on baby’s movements while
interacting with environment
Perceptual Development
- newborns indicate taste preferences by facial expressing and by choosing to
swallow of not swallow different liquids
- newborns prefer odour of mother’s breast than to other women
- can recognize and prefer mother’s voice
Perception Patterns
- babies not perceiving complete shapes, their scanning strategy is limited to
fixations on few parts of object at which they are looking
- prefer to look at stimuli that resembles human face
Perception of Space
- “visual cliff” – ability to perceive 3-dimensional space; most babies would not
crawl over glass shelf for fear of falling
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-Critical period: a specific time in development during which certain experiences
must occur for normal development to occur
- many behavioural, perceptual and cognitive abilities are subject to critical periods
(i.e. if infants are not exposed to a stimulating environment and do not have
opportunity to interact with caregivers during first 2 yrs of lives, cognitive
development will be impaired.)
Importance of Responsive Environment
- cognitive development in infants is process by which they get to know things about
themselves and their world
- involve evolutionary and environmental variables
- learn that events in environment can be dependent on one’s own behaviour
- experiment: 3 groups of infants presented with a mobile 10 min/day for 14 days;
pillow containing pressure-sensitive switch placed under baby’s head – mobile was
suspended above baby’s face
- group 1: mobile automatically rotated whenever infant moved hi/her head and
activated switch – controlled the mobile’s movements
- group 2: mobile remained stationary
- group 3: mobile intermittently moved on its own but not in response to infant head
- group 1 learned they could control movements of mobile
- babies raised in unresponsive, unstimulating institutions – limited opportunities to
learn they could affect others/no individual attention from caregivers
- these children were extremely impaired in cognitive, language and motor
The Work of Jean Piaget
- Jean Piaget, Swiss psychologist – viewed cognitive development as maturation
- Based his conclusions on observations of behaviour of children
- Noticed that children of similar age tend to engage in similar behaviours and make
same kinds of mistakes in problem solving
- Concluded that these similarities are result of sequence of development that all
normal children follow
- Completion of each period with its corresponding abilities is prerequisite to next
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