Heredity and Environment

1
Lecture 3

• Heredity and Environment
• Prenatal Development
• Birth

2
Heredity and environment

• The case of intelligence

3
Charles Darwin

• Observed that most organisms reproduce at
  tremendous rates, yet populations remain nearly
  constant.
• Reasoned that an intense, constant struggle for
  food, water, and resources must occur among the
  numerous young born.
• Those that survive pass on their genes to the
  next generation.
• Believed that those who survive are superior to
  those who do not.

4
Natural Selection

• Natural selection is the evolutionary process
  that favors individuals of a species that are
  more adapted to survive and reproduce.

5
Francis Galton (1822-1911)

• Galton Intelligence is a matter of sensory
  acuity.
• Sensory acuity mainly a function of natural
  endowment ? Intelligence inherited.
• Children of illustrious individuals are far more
  likely to be illustrious themselves.
• Eugenics -gt Selective breeding.

6
Alphonse de Candolle (1806-1893)

• Climate, religious tolerance, democratic
  government, and a thriving economy are at least
  as important as inherited capacity.
• Galton -gt
• Intelligence tests
• Concept of Correlation
• Twins studies

7
Modern Twin Studies

• The behavioral similarity of identical twins is
  compared with the behavioral similarity of
  fraternal twins.
• Identical twins (monozygotic twins) develop from
  a single fertilized egg that splits into two
  genetically identical replicas, each of which
  becomes a person.
• Fraternal twins (dizygotic twins) develop from
  separate eggs and separate sperm, making them
  genetically no more similar than ordinary
  siblings.

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Issues with Twin Studies

• By comparing groups of identical and fraternal
  twins, behavior geneticists capitalize on the
  basic knowledge that identical twins are more
  similar genetically than are fraternal twins.
• However, adults might stress the similarities of
  identical twins more than those of fraternal
  twins.
• Identical twins might perceive themselves as a
  set and play together more than fraternal twins.

9
Alfred Binet (1857-1911)

• First Binet turned to the favored method of Paul
  Broca ? Measured skulls
• By the end The idea of measuring intelligence
  by measuring heads seemed ridiculous.
• 1904 Psychological methods.
• Series of short tasks, related to everyday
  problems of life.
• ? Mental age and Chronological age.
• ? Special educational programs.

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W. Stern (1871-1938)

• Mental age should be divided by chronological age
  ? Intelligence quotient (IQ).

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Binets approach

• The scores are a practical device.
• The scale is an empirical guide for identifying
  children who need help.
• Emphasis upon improvement through special
  training.

12
USA

• Intelligence Means of power and control.
• Identification of the so called feeble-minded
  within the USA. Goal prevent procreation
  (eugenics).
• Restriction on immigration of so-called inferior
  races from Europe.
• Legitimizing oppression of African Americans by
  suggesting that they intellectually inferior.

13
American psychologists hereditarian theory of IQ.

• Binet's scores Measures of an entity called
  intelligence.
• Intelligence Largely inherited
• Inherited IQ scores Marked people and groups for
  an inevitable station in life.
• Differences between groups Heredity

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Problems

• Conceptual problem.
• Equation of "heritable" with "inevitable.
• Confusion of within and between-group heredity.
• ? Statistical definition of heritability.
• ? Range of reactions.
• ? If heredity explains a certain percentage of
  variation among individuals within a group, it
  must also explain a similar percentage of the
  difference in average IQ between groups ? wrong
  (two separate phenomena).

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Henry Goddard (1866-1957)

• Translated the Binet-Simon scale into English.
• "It is perfectly clear that no feeble-minded
  person should ever be allowed to marry or to
  become a parent.
• ? 20 states passed sterilization laws.
• Idiots Imbeciles Morons.
• Immigration specified European countries for
  which the percentage of mentally defective
  immigrants was the highest.

16
Lewis Terman (1877-1956)

• Revised the Binet scale and made it popular. IQ
  MA/CA100.
• Children should be segregated in special classes
  and be given instruction which is concrete and
  practical.

17
Robert M. Yerkes (1876-1956)

• Army Alpha Test Literate individuals. Army Beta
  Test Illiterate individuals
• Results About half of the white males tested
  in the army had a mental age of 13 or lower.
• European immigrants can be graded by their
  country of origin.
• Blacks lacks initiative, displays little or no
  leadership, and cannot accept responsibility.
• ? Immigration Restriction Act of 1924. Quotas
  against nations of "inferior stock."

18
US Black-White mental testing

• 1897 G. R. Stetson tested 500 African American
  and 500 European American public school children
  in Washington, D.C.
• Children were required to repeat four stanzas of
  poetry.
• Black children outperformed the white children ?
  Memory not a valid measure of intelligence.

19
Intelligence

• Arthur Jensen sparked a debate theorizing that
  intelligence is primarily inherited. Differences
  between races are inherited.
• Flynn effect
• Average IQ test score performance is rapidly
  rising.
• The largest Flynn effects appear on so-called
  culture fair tests
• Dutch data shows a 21 point difference between
  1952 and 1982.

20
Down Syndrome

• Caused by the presence of an extra chromosome
• Characterized by
• round face
• flattened skull
• extra fold of skin over the eyelids
• protruding tongue
• short limbs
• retardation of motor and mental abilities

21
John Langdon H. Down

• Physician to the Asylum for Idiots at Earlswood.
• 1860s Investigations into the 'structure and
  function of the various organs' in idiots and
  imbeciles.
• Classify idiots on the basis of their resemblance
  to ethnic groups.
• Facial features and behavioral attributes of
  certain idiots -gt typical Mongols.

22
Conclusions about Heredity-Environment Interaction

• Both genes and environment are necessary for a
  person to exist.
• The emerging view is that genes give people a
  propensity for a particular developmental
  trajectory that is ultimately realized through
  environmental circumstances.

23
Prenatal Development

• From a zygote, a single cell, the size of a
  period in your book, to 2 billion cells and
  weighing over 3kgs.

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The Process of Human Reproduction

• Reproduction begins when an ovum is fertilized by
  a sperm.
• This produces a zygotea single cell formed
  through fertilization.
• In the zygote, two sets of unpaired chromosomes
  combine to form one set of paired chromosomes.

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The Course of Prenatal Development

• The Germinal Period
• The Embryonic Period
• The Fetal Period

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The Germinal Period

• It is the period that occurs the first 2 weeks
  after conception.
• By about 1 week after conception, the zygote is
  composed of 100 to 150 cells.
• This period includes the creation of the zygote,
  continued cell division, and attachment of the
  zygote to the uterine wall.
• Implantation, or attachment to the uterine wall,
  occurs about 10 days after conception.

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The Differentiation of Cells

• The Blastocyst - the inner layer of cells that
  develops during the germinal period and later
  becomes the embryo
• The Trophoblast - the outer layer of cells that
  develops during the germinal period and later
  provides nutrition and support for the embryo

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The Embryonic Period

• The period that occurs from 2 to 8 weeks after
  conception
• The rate of cell differentiation intensifies,
  support systems for the cells form, and organs
  appear

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Cell Layers of the Embryo

• Endoderm - inner layer develops into the
  digestive and respiratory systems
• Ectoderm - outermost layer becomes the nervous
  system, sensory receptors (ears, nose, eyes), and
  skin parts (hair and nails)
• Mesoderm - middle layer becomes the circulatory
  system, bones, muscles, excretory system, and
  reproductive system

30
Prenatal Life-Support Systems

• The Placenta - consists of a disk-shaped group of
  tissues in which small blood vessels from the
  mother and the offspring intertwine but do not
  join
• The Umbilical Cord - contains two arteries and
  one vein, that connects the baby to the placenta
• The Amnion - a bag or envelope that contains a
  clear fluid in which the developing embryo floats

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Important Embryonic Developments

• 21 Days - Eyes begin to appear
• 24 Days - Heart cells begin to differentiate
• Fourth Week - First appearance of the urogenital
  system, arm and leg buds appear, chambers of the
  heart take shape, blood vessels surface
• Fifth to Eighth Week - Arms and legs
  differentiate further, face starts to form,
  facial structures
• 8 Weeks - 2.5 cm long

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Definition of Organogenesis

• The process of organ formation that takes place
  during the first 2 months of prenatal development

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The Fetal Period

• The period that begins 2 months after
  conception and lasts, on average, 7 months

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Three Months after Conception

• The fetus is 7.5 cm long.
• The fetus becomes active, moving its arms, legs,
  head, and opening and closing its mouth.

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The End of the Fourth Month

• The fetus is 15 cm. long.
• Arm and leg movements can be felt by the mother
  for the first time.

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The End of the Fifth Month

• The fetus is 30 cm long.

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The End of the Sixth Month

• The fetus is approximately 35 cm long.
• A grasping reflex is present.

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The End of the Seventh Month

• The fetus is 40 cm long.
• The fetus is very active.

39
The Eighth and Ninth Months

• The fetus grows longer and gains substantial
  weight.
• At birth, the average North American baby is
  about 51 cm long and weighs 3.2 kg.

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Prenatal Diagnostic Tests

• Maternal Blood Test
• Ultrasound Sonography
• Amniocentesis
• Chorionic Villi Sampling

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Amniocentesis

• A prenatal medical procedure in which a sample of
  amniotic fluid is withdrawn by syringe and tested
  to discover if the fetus is suffering from any
  chromosomal or metabolic disorders
• Performed between the 12th and 16th weeks of
  pregnancy
• There exists a small risk of miscarriage (one in
  every 200-300)

42
Chorionic Villi Sampling

• A prenatal medical procedure in which a small
  sample of the placenta is removed
• Performed between the 8th and 11th weeks of
  pregnancy
• Provides information about the presence of birth
  defects
• Has a slightly higher risk of miscarriage than
  amniocentesis

43
Sensory Capacities of the Fetus

• Motion The vestibular system of the middle ear
  begins to function in the human fetus about 5
  months after conception and is fully mature at
  birth.
• Vision Little is known for certain. At 26 weeks
  of pregnancy, fetuses respond to light it causes
  their heart rate to change.
• Sound Research indicates that at 4 months after
  conception the fetus is able to respond to sound.

44
Teratology

• Teratology - The field of study that investigates
  the causes of birth defects.
• Teratogen - Any agent that causes a birth defect.
• Numerous teratogens exist, thus almost every
  fetus is exposed to at least some.
• It may take a long time for the effects of a
  teratogen to show up.
• Only about half of all potential effects appear
  at birth.

45
Sensitivity during Organogenesis

• The probability of a structural defect is
  greatest during organogenesis.
• 15 - 25 days after conception, the brain is most
  vulnerable.
• 24 - 40 days after conception, the eyes are most
  vulnerable.
• 20 - 40 days after conception, the heart is most
  vulnerable.
• 24 - 36 days after conception, the legs are most
  vulnerable.

46
Sensitivity during the Fetal Period

• Exposure is less likely to cause anatomical
  defects.
• Exposure is more likely to stunt growth.
• Exposure is more likely to create problems in
  organ functioning.

47
Prescription and Nonprescription Drugs

• Both can have possible effects on the fetus.
• A tragic example is with the tranquilizer
  thalidomide, prescribed in the early 1960s.
• Mothers do not have to be chronic drug users for
  the fetus to be harmed.
• Taking the wrong drug at the wrong time is enough
  to physically handicap offspring for life.

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Prescription Drugs that Can Function as Teratogens

• Antibiotics (streptomycin, tetracycline)

49
Nonprescription Drugs that Can Function as
Teratogens

• Diet Pills
• Aspirin
• Caffeine
• FDA recommends either no caffeine or very little.

50
Alcohol

• Heavy Drinking
• Moderate Drinking

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Heavy Drinking during Pregnancy

• Fetal Alcohol Syndrome (FAS) - A cluster of
  abnormalities that appears in the offspring of
  mothers who drink alcohol heavily during
  pregnancy
• Facial deformities
• Defective limbs, face, and heart
• Below average intelligence, with some cases of
  mental retardation
• Adults with FAS found to have a high incidence of
  mental disorders, such as depression or anxiety

52
Nicotine

• Fetal and neonatal deaths are higher among
  smoking mothers.
• There exists a higher incidence of preterm births
  and lower birthweights.

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Environmental Hazards

• Radiation nuclear environments, X-rays, computer
  monitors
• Chemicals carbon monoxide, mercury, lead,
  pesticides, PCBs
• Heat saunas, hot tubs

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Other Maternal Factors

• Infectious Diseases
• Nutrition
• Emotional States and Stress
• Maternal Age

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Effects of Stress on Pregnancy

• Mothers stress can be transmitted to the fetus.
• When a pregnant woman experiences intense fears,
  anxieties, and other emotions, physiological
  changes occur.
• These affect the fetus through, for example,
  restricting blood flow to the uterine area
  depriving the fetus of adequate oxygen.

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Maternal Age

• Adolescence
• The Thirties and Beyond

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The Thirties and Beyond

• The risk of Down Syndrome increases after the
  mother reaches age 30.
• Women have more difficulty getting pregnant after
  the age of 30.
• As women remain active, exercise regularly, and
  are careful about their nutrition, their
  reproductive systems may remain healthier at
  older ages.

58
Paternal Factors

• Mens exposure to lead, radiation, certain
  pesticides, and petrochemicals may cause
  abnormalities in sperm that lead to miscarriage
  or disease.
• When fathers have a diet low in vitamin C, their
  offspring have a higher risk of birth defects and
  cancer.
• Fathers smoking during pregnancy may lead to
  lower birthweight and potential for their
  offspring developing cancer.
• Older fathers may place their offspring at risk
  for certain birth defects, such as Down syndrome
  and dwarfism.

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The Birth Process

• Stages of Birth
• The Fetus/Newborn Transition

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The First Stage of Birth

• This is the longest of the three stages, lasting
  an average of 12-24 hours.
• Uterine contractions are 15-20 minutes apart and
  last up to 1 minute.
• Contractions cause cervix to stretch and open.
• Contractions get closer together as the stage
  progresses.
• By the end of this stage the cervix is dilated to
  about 10 cm.

61
The Second Stage of Birth

• This stage begins when the babys head starts to
  move through the cervix and the birth canal.
• It terminates when the baby completely emerges
  from the mothers body.
• This stage lasts about one and a half hours, and
  involves the mother bearing down to push the baby
  out.
• Contractions come about every minute and last
  about a minute.

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The Third Stage of Birth

• This stage is called afterbirth and lasts only
  minutes.
• It involves the detachment and expulsion of the
  placenta, umbilical cord, and other membranes.

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The Fetus/Newborn Transition

• Being born involves considerable stress for the
  baby.
• Anoxia (the condition in which the fetus/newborn
  has an insufficient supply of oxygen) can cause
  brain damage, and is a concern if delivery takes
  too long.
• After the umbilical cord is cut, 25 million air
  sacs in the lungs must fill with air.
• The newborns bloodstream is redirected through
  the lungs and to all parts of the body.
• The baby is born with a protective covering of
  skin grease called vernix caseosa which is
  cleaned off.

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The baby's experience of birth

• Otto Rank (1884-1937) Birth trauma, rather than
  the Oedipus complex central position in the
  causation of psychoneurosis.
• Hugo Lagercrantz and Theodore Slotkin (1986) As
  the birth process begins, a surge in the
  production of adrenaline and other stress
  hormones protect him/her from adverse conditions.
• Lagercrantz and Slotkin point out that infants
  delivered by cesarean section often have
  difficulty breathing.

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Cesarean Delivery

• The baby is removed from the mothers uterus
  through an incision made in her abdomen.
• Usually performed if the baby is in a breech
  position, causing the babys buttocks to emerge
  from the vagina first.

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Measures of Neonatal Health and Responsiveness

• The Apgar Scale
• The Brazelton Neonatal Behavioral Assessment Scale

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The Apgar Scale

• A method widely used to assess the health of
  newborns at 1 and 5 minutes after birth.
• It evaluates infants
• heart rate
• respiratory effort
• muscle tone
• body color
• reflex irritability
• Obstetrician or nurse assesses the newborn and
  gives a score of 0, 1, or 2 on each item.
• A score of 7-10 is good, 5 indicates possible
  developmental difficulties, 3 or below signals an
  emergency.

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The Brazelton Neonatal Behavioral Assessment Scale

• Performed within 24-36 hours after birth to
  evaluate neurological development, reflexes, and
  reactions to people.
• The newborn is rated on each of 27 items,
  contributing to four categories physiological,
  motoric, state, and interaction.
• Babies are also given global classification such
  as worrisome, normal, superior.

69
Parent-child relationship

• Bonding is the occurrence of close contact
  between parents and newborn in the period shortly
  after birth.
• Research supports the importance of bonding, but
  challenges the significance of the first few days
  of life as a critical period.