PSYA02H3 Chapter Notes - Chapter 10: Fetus, Synaptogenesis, Blastocyst

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21 Mar 2015

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PSYA02 Chapter 10 Notes
10.1 – Physical Development from Conception through Infancy
-Development psychology: The study of human physical, cognitive, social, and behavioural
characteristics across the life span
-Cross-sectional design: Used to measure and compare samples of people at different ages at a given
point in time
oIf you study cognition from infancy to adulthood, you could compare people of different age
oRelatively cheap, quick, and easy to administer
oCohort effects: Differences between people that result from being born in different time periods
If you find differences between people born last year with those born in the 1990s, this
may reflect any number of differences between people from those time periods (nutrition,
medical advances, cultural changes)
-Longitudinal design: Follows the development of the same set of individuals through time
oSelecting a sample of infants and measuring their cognitive development periodically over the
course of 20 years
oFixes the problem of cohort effects, but the demands of following a single group of people for a
long period of time can be very costly and time-consuming
oAttrition: Occurs when participants drop out of a study for some reason, such as losing interest or
moving away
- To account for both periods of slow and rapid growth, development is seen as a progression of abrupt
transitions in physical or mental skills, intersperse with slower, more gradual change (series of stages)
oShifts in thinking and behaving, and fundamental shifts in the types of abilities a child can
- Complex interactions between genetics and the environment are constantly shaping development when
individuals are particularly sensitive to the stimulation that facilitates physiological, neurological,
behavioural, and cognitive development
-Sensitive period: A window of time during which exposure to a specific type of environmental
stimulation is needed for normal development of a specific ability
oInfants need to be exposed to speech during their first few years of life to become fluent in their
own language
oLong term deficits can emerge if the needed stimulation, such as language, is missing during a
sensitive period
oAbilities such as depth perception, balance, and recognition of parents
Quick Quiz 10.1a
1) The effects of language deprivation during infancy and childhood can be irreversible. This fact is best
explained by which concept? Sensitive period
2) A researcher has only one year to complete a study on a topic that spans the entire range of childhood
TO complete the study she should use a cross-sectional design
3) Which of the following is a factor that would be LEAST likely to be a cohort effect for a study on
cognitive development in healthy people? Differences in genes between healthy people
-Zygote: The initial cell formed when the nuclei of egg and sperm fuse
-Germinal stage: The first phase of prenatal development, which spans from conception to two weeks
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oZygote divides into two cells, then four, then eight, and so on, travelling down the fallopian tubes
toward the uterus, where it becomes implanted into the lining of the uterus
oBlastocyst, ball of cells, splits into two groups, with the inner group of cells developing into the
fetus, while the outer group of cells forming the placenta (passes oxygen and nutrients to, and to
expel from, the fetus)
-Embryonic stage: Spans weeks two through eight, during which time the embryo begins developing
major physical structures such as the heart and nervous system, as well as the beginnings of arms, legs,
hands, and feet
oBrain is first seen, between the second and third weeks of gestation, when some cells migrate to
the appropriate locations and begin to differentiate into nerve cells
-Fetal stage: Spans week eight through birth, during which time the skeletal, organ, and nervous systems
become more developed and specialized
oMuscles develop and the fetus begins to move, sleep and wake cycles start, and the fetus is
responsive to external cues
- By 11 weeks, differentiations between the cerebral hemisphere, the cerebellum, and the brain stem are
-Myelination: During the final months of pregnancy, a fatty tissue called myelin builds up around
developing nerve cells
- Newborns have an estimated 100 billion neurons and a brain that is approximately 25% the size and
weight of an adult brain
o4000 new neurons per second in the womb
- Human brains develop most of their neural organization through interaction with the outside
oAnimal brains develop predominantly in the womb
oHuman children and adults are able to adapt to the challenges of just about any environment on
earth (becoming the type of organism we need to be in the environment)
- Nutrition is critical for normal fetal development; single most important non-genetic factor affecting
fetal development
- Pregnant women require an almost 20% increase in energy intake during pregnancy, including sufficient
quantities of protein (which affects neurological development) and essential nutrients (especially omega-
3 fatty acids, folic acid, zinc, calcium, and magnesium)
- Fetal malnutrition can have severe consequences, producing low-birth-weight babies who are more
likely to suffer from a variety of diseases and illnesses, and are more likely to have cognitive deficits
that can persist long after birth
oDifficulties controlling their emotions, due to underdeveloped prefrontal cortices and other brain
areas involved in self-control
oBabies born in the WWII famine experienced physical problems, and were at higher risk of
developing psychological disorders such as schizophrenia and anti-social personality disorder
oTeratogens: Substances, such as drugs or environmental toxins, that impair the process of
Thalidomide: A sedative that was hailed as a wonder drug for helping pregnant women
deal with morning sickness during pregnancy, but was disastrous because it caused
miscarriages, severe birth defects (blindness and deafness), and phocomelia (victims
hands, feet, or both emerged directly from their shoulders or hips like flippers)
20,000 babies were affected
oAlcohol and tobacco are common too
-Fetal alcohol syndrome: Involves abnormalities in mental functioning, growth, and facial development
in the offspring of women who use alcohol during pregnancy
oAlcohol passes through the placental membranes, leaving the developing fetus vulnerable to its
effects, which include reduced mental functioning
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- Smoking can expose the developing fetus to teratogens, decreasing blood oxygen and raising
concentration of nicotine and carbon monoxide, as well as increasing the risk of miscarriage or death
during infancy
oBabies are twice as likely to have low birth weight and have a 30% chance of premature birth
oProblems with emotional development and impulse control as well as attentional problems
Quick Quiz 10.1b
1) A developing human is called an embryo during the time between weeks 2 and 8
2) In which stage do the skeletal, organ, and nervous systems become more developed and specialized?
Fetal stage
3) Which of the following would qualify as a teratogen? Cigarette smoke, alcohol, and prescription drug
4) Which of the following statements best summarizes the effects of preterm birth? Preterm birth may
cause physical and cognitive problems
- Human infants depend entirely on caregivers to keep them alive, as they slowly develop their senses,
strength, and coordination
- By seven to eight months, infants can hear and actively listen, as the brain starts receiving signals from
the eyes and ears
- Newborn babies show a preference for their mother’s voice over other women’s voices
oQueens University research showed that babies responded positively when they heard poems
read in their moms voices but not when read by a stranger
oBabies up to at least 4 months old don’t prefer their father’s voice over other mens
- Auditory patterning of babies brains is so significant that they have already started to internalize the
sounds of their own native tongue, even before they are born
oBabies actually cry with an accent (cries of French babies rose in intensity toward the end of
their cry while German babies started at high intensity and then trailed off)
oActively learning about their cultural environment even while in the womb
- Visual system is not as well developed at birth
oNewborns have only about 1/40th of the visual acuity of adults, and can only see about as far
away as is necessary to see their mom’s face while breastfeeding (about 30cm or less)
oColour vision happens at about 2 months of age, depth perception at 4 months, and shape
discrimination at 8 months
- By a few days of age, newborns will imitate the facial expressions of others; they prefer to look at
stimuli that look like faces, compared to stimuli that have all the same features but are scrambled so that
they don’t look like faces
oStudy showed that within one hour of birth, newborns begin to imitate facial expressions
- Visual system develops in response to the infant experiencing a world of diverse visual input
oMcMaster University research has shown that even though babies possess the necessary
“equipment” for proper vision, this equipment needs to be exposed to a divers visual world in
order to learn how to function effectively
- The taste and olfactory systems are relatively well developed at birth; newborns cringe when smelling
something rotten or pungent, such as ammonia, and they show preference to sweets
oThey can smell the difference in their mother’s breast milk compared to a stranger
- The beginnings of the motor system develop very early; a mere five months after conception, the fetus
begins to have control of voluntary motor movements
oReflexes: Involuntary muscular reactions to specific types of stimulation
Provide newborns and infants with a set of innate responses for feeding and interacting
with their caregivers
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