Psychology 1000 Chapter Notes - Chapter 12: Umbilical Cord, Testis Determining Factor, Sexually Transmitted Infection
13 May 2018
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Development over the Lifespan!
•Developmental psychology examines changes in our biological, physical, psychological,
and behavioural processes as we age. !
• to investigate age-related changes!
• Suppose we wish to study how intellectual abilities change from age 10 to age 60
we use a cross-sectional design, we would compare people of different ages at
the same point in time. !
•we could administer intellectual tasks to 10-, 20-, 30-, 40-, 50-, and 60-year-
olds. !
•We would test each person and compare how well the different age groups
perform. !
•The cross-sectional design is widely used because data from many age
groups can be collected relatively quickly, but a key drawback is that the
different age groups, called cohorts, grew up in different historical periods. !
•Thus, if 60-year-olds have poorer intellectual abilities than 30-year-
olds, is this due to aging or environmental differences !
•A longitudinal design repeatedly tests the same cohort as it grows older. !
•We could test a sample of 10-year-olds this month and then retest them
every 10 years, up to age 60, thus ensuring that everyone is exposed to the
same historical time frame. !
•Unfortunately, a longitudinal design is time-consuming and, as years pass,
our sample may shrink substantially as people move, drop out of the study,
or die. !
•sequential design combines the cross-sectional and longitudinal approaches. !
•That is, we can repeatedly test several age cohorts as they grow older and
determine whether they follow a similar developmental pattern. !
•the most time-consuming and costly.!
PRENATAL DEVELOPMENT!
•Prenatal development consists of three stages of physical growth. !
1. The germinal stage constitutes approximately the first two weeks of development,
beginning when one sperm fertilizes a female egg (ovum). !
•This fertilized egg is called a zygote. !
•Through repeated cell division the zygote becomes a mass of cells that
attaches to the mother's uterus about 10 to 14 days after conception.!
2. The embryonic stage extends from the end of the second week through the eighth
week after conception, and the cell mass now is called an embryo. !
•Two life-support structures, the placenta and umbilical cord, develop at the
start of this stage. !
•Located on the uterine wall, the placenta contains membranes that allow
nutrients to pass from the mother's blood to the umbilical cord. !
3. The umbilical cord contains blood vessels that carry these nutrients and oxygen to
the embryo, and waste products back from the embryo to the mother. !
•Supplied with nutrients, embryonic cells divide rapidly and become
specialized. !
•Bodily organs and systems begin to form, and by week eight the heart of the
two-centimetre-long embryo is beating, the brain is forming, and facial
features, such as eyes, can be recognized.!
4. At the ninth week after conception, the embryo is called a fetus. !
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•During this fetal stage, which lasts until birth, muscles become stronger and
other bodily systems continue to develop. At about 24 weeks the eyes open,
and by 28 weeks the fetus attains the age of viability, meaning that it is likely to
survive outside the womb !
Genetics and Sex Determination
•A female's egg cells and a male's sperm cells each have only 23 chromosomes. At
conception, an egg and sperm unite to form the zygote, which now contains the full set of
23 pairs!
•The 23rd pair of chromosomes determines the baby's sex.!
• The Y chromosome contains a specific gene, known as the TDF (testis determining factor)
gene, that triggers male sexual development!
•How does the Y chromosome determine male sex characteristics? !
•At roughly six to eight weeks after conception, the TDF gene initiates the
development of testes. Once formed, the testes secrete sex hormones called
androgens that continue to direct a male pattern of organ development. !
Environmental Influences
•Teratogens are environmental agents that cause abnormal prenatal development. !
• For example, if the mother contracts rubella (German measles)—especially when
the embryo's eyes, ears, heart, and central nervous system are beginning to form
early in pregnancy—it can cause blindness, deafness, heart defects, and intellectual
disability in the infant !
•Sexually transmitted diseases can pass from mother to fetus and produce brain damage,
blindness, and deafness, depending on the disease. !
•Among pregnant women with untreated syphilis, about 25 percent of fetuses are
born dead. !
• Without treatment during pregnancy or delivery by Cesarean section, about 25
percent of fetuses born to mothers with human immunodeficiency virus (HIV) also
are infected !
• Fetal alcohol spectrum disorders (FASD) involve a range of mild to severe cognitive,
behavioural, and physical deficits caused by prenatal exposure to alcohol !
•One disorder within this spectrum, fetal alcohol syndrome (FAS), involves a cluster
of severe developmental abnormalities.!
• FAS children have facial abnormalities and small, malformed brains !
•Psychological and social impairments include intellectual disability,
attentional and perceptual deficits, impulsivity, and poor social skills!
•The threshold levels of alcohol exposure needed to produce FASD, or FAS
specifically, are not known. About one-third to one-half of infants born to alcoholic
mothers have FAS, but even social drinking or a single episode of binge drinking
can increase the risk of prenatal damage and long-term cognitive impairment.!
•Nicotine is another teratogen. Maternal smoking increases the risk of miscarriage,
premature birth, and low birth weight !
• Because of second-hand smoke, regular tobacco use by fathers also has been
linked to low infant birth weight and increased risk of respiratory infections !
•Babies of pregnant mothers who use heroin or cocaine are often born addicted and
experience withdrawal symptoms after birth. !
•Their cognitive functioning, motor skill development, and ability to regulate their
arousal and attention may also be impaired!
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INFANCY AND CHILDHOOD!
•During research studies, infants may start to fuss, cry, drool, spit up, soil their diapers, or
simply fall asleep! !
•Experiments must be designed to keep infants alert and “on task,” a difficult job
because they are easily overwhelmed by novel, highly stimulating environments and
rapidly become bored by bland environments. !
•Finally, because infants can't describe their experiences, researchers must find clever ways
to use those responses that infants can make, such as sucking and looking, to draw
inferences about their capabilities and preferences.!
Newborn Sensation and Perception
•Infants are very nearsighted; their visual acuity is about 20/800!
•infants can focus on an object 20 to 40 cm away, the distance to the mother's face
for a breastfeeding infant. !
•Robert Fantz (1961) used the preferential looking procedure to study infants' visual
preferences. !
•He placed infants on their backs, showed them two or more stimuli at the same
time, and filmed their eyes to record how long they looked at each stimulus. !
•Infants preferred complex patterns, such as realistic or scrambled drawings of a
human face, to simple patterns and solid colours!
•Newborns readily turn toward off-centred auditory (e.g., rattles or voices sounded opposite
one ear) and tactile (e.g., touching the cheek) targets and odours !
•Newborns orient to significant stimuli in their environment, the most important being their
mother's face, voice, and smell, optimizing their access to food, warmth, and social
stimulation.!
Newborn Learning
•Infants appear to learn rapidly. Within 72 hours of birth, they distinguish the familiar face of
their mother from that of a female stranger—they look longer at their mother's face !
•They usually look longer at a novel rather than familiar stimulus !
•Philip Zelazo and colleagues at McGill University used an auditory habituation procedure to
study infant memory. !
•They recorded two-day-olds' head-turning toward an off-centred, recorded speech
sound (e.g., “Tinder”). !
•After about 16 presentations, infants stopped turning to face the now familiar
sound. !
•They were not simply fatigued because !
•(1) by the end of habituation, many infants were turning away from the
sound, perhaps trying to avoid it!
•(2) they readily turned toward a novel sound (e.g., “Beagle”), indicating that
they could discriminate between some adult speech sounds!
•(3) partial habituation to the sound lasted for at least 24 hours. !
•Newborns can learn through classical and operant conditioning, and imitation. !
•Blass, Ganchrow, and Steiner (1984) followed a touch on newborns' foreheads (the
CS) with the delivery of milk to their mouths (the UCS). After a few pairings,
newborns turned toward the food source and puckered their lips (the UCR) during
the CS. When the food was withheld during extinction, they cried, reflecting that
they were upset when learned expectancies were violated.!
•Meltzoff and Moore (1977, 2000) reported that newborns will imitate some adult facial
expressions !
•They suggest that this innate ability helps infants recognize people and engage them in
social exchange.!
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