Transcript Section Two

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Chapter 3
Biological Beginnings
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“There are one hundred and ninety-three
living species of monkeys and apes.
One hundred and ninety-two of them
are covered with hair. The exception is
the naked ape, self-named Homo
sapiens.”
- Desmond Morris
British Zoologist, 20th Century
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Learning Goals
1. Discuss the evolutionary perspective.
2. Describe the genetic foundation of
development.
3. Identify important reproduction challenges
and choices.
4. Explain heredity-environment interaction.
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Biological Beginnings
The Evolutionary
Perspective
Genetic
Foundations
Reproduction
Challenges
and Choices
HeredityEnvironment
Interaction
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The Evolutionary
Perspective
Natural Selection
and Adaptive
Behavior
Evolutionary
Psychology
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Natural Selection
• Natural selection is the
evolutionary process that favors
individuals of a species that are
more adapted to survive and
reproduce.
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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.
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Adaptive Behavior
• Promotes an organism’s survival in the natural habitat.
• Modification of an organism’s behavior to include its
likelihood of survival.
• All organisms must adapt to particular places, climates,
food sources, and ways of life.
• Natural selection designs adaptation to perform a certain
function.
• Attachment is a system designed by natural selection to
ensure a human infant’s closeness to the caregiver for
feeding and protection from danger.
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Evolutionary Psychology
• Emphasizes the importance of adaptation, reproduction,
and “survival of the fittest” in explaining behavior.
• Focuses on conditions that allow survival or to failure.
• Natural selection favors behaviors that increase organisms’
reproductive success and their ability to pass their genes on
the next generation.
• Evolutionary Psychologist, David Buss believes that
evolution shapes both our physical features and influences
decision-making, aggressiveness, fear, and mating habits.
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Evolution and Life-Span
Development
• Developmentalist Paul Baltes believes
that the benefits of evolutionary
selection decrease with age.
• He also believes that the need for
culture increases with age.
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The Benefits of Evolutionary
Selection Decrease with Age
• Selection operates mainly during the first half of
life during the period of reproductive fitness.
• Given the much shorter life span in early human
evolution, selection pressure could not function
often in the later years of life.
• This results in older adults having a higher number
of deleterious genes and dysfunctional gene
expressions, such as Alzheimer’s.
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The Need for Culture
Increases with Age
• As older adults weaken biologically, they need
culture-based resources, such as cognitive skills,
motivation, socialization, literacy, and medical
technology.
• Baltes stresses that a life span shift in the
allocation of resources takes place away from
growth and toward maintenance
and the regulation of loss.
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Evaluating Evolutionary
Psychology
• Albert Bandura
• Steven Jay Gould
• Theodore Dobzhansky
• The Bidirectional View
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Albert Bandura
• Acknowledges the important influence of
evolution on human adaptation and change
• Rejects “one-sided evolutionism”—defining
social behavior as the product of evolved
biology
• Believes the pace of social change gives
testimony that biology permits a range of
possibilities
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Steven Jay Gould
• Concluded that in most domains of human
functioning, biology allows a broad range of
cultural possibilities
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Theodore Dobzhansky
• Points out that the human species has been
selected for learnability and plasticity,
allowing us to adapt to diverse contexts
rather than have our behavior be
biologically fixed
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The Bidirectional View
• Evolutionary pressures created changes in
biological structures for the use of tools.
• This enables organisms to manipulate, alter, and
construct new environmental conditions.
• Environmental innovations of increasing
complexity, in turn, produced new selection
pressures for the evolution of specialized
biological systems for consciousness, thought,
and language.
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Genetic
Foundations
What Are
Genes?
Mitosis and
Meiosis
Genetic
Principles
Behavior
Genetics
Molecular
Genetics
Chromosome
and GeneLinked
Abnormalities
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Genetic Foundations
• Each of us carries a genetic code that we
inherited from our parents.
• This code is located within every cell in our
bodies.
• The code is the mechanism for transmitting
characteristics from one generation to the
next.
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Genetic Building Blocks
• DNA
• Genes
• Chromosomes
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Definition of DNA
• Deoxyribonucleic acid (DNA) is
a complex molecule, shaped like
a double helix, that contains
genetic information.
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What Are Genes?
• The units of hereditary
information—short segments
composed of DNA—that act as a
blueprint for cells to reproduce
themselves and manufacture the
proteins that maintain life.
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Definition of Chromosomes
• Threadlike structures comprised
of thousands of genes, that
come in 23 pairs, one member
of each pair coming from each
parent
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Mitosis and Meiosis
• Mitosis is the process of cell division by
which each chromosome in the cell’s
nucleus duplicates itself.
• Meiosis is the process by which cells in the
reproductive organs divide into gametes
(sperm in males, eggs in females), which
have half the genetic material of the parent
cell.
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The Difference Between
Mitosis and Meiosis
• Mitosis
– Focus is on cell growth
and repair
– The number of
chromosomes present
remains the same (the
chromosomes copy
themselves)
– Two daughter cells are
formed
• Meiosis
– Involves sexual
reproduction
– The chromosomes are
halved
– Four daughter cells are
produced
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The Process of Human
Reproduction
• Reproduction begins when a female
gamete (ovum) is fertilized by a male
gamete (sperm).
• This produces a zygote—a 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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Genetic Principles
•
•
•
•
•
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Dominant-recessive genes principle
Sex-linked genes
Genetic Imprinting
Polygenically inherited characteristics
Reaction range
Canalization
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Dominant-Recessive Genes
Principle
• If one gene of a pair is dominant and
one is recessive, the dominant gene
exerts its effect, overriding the
potential influence of the other,
recessive gene.
• A recessive gene exerts its influence
only if the two genes of a pair are both
recessive.
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Sex-Linked Genes
• Two of the 46 chromosomes
human beings normally carry are
sex chromosomes. Ordinarily
females have two X chromosomes
and males have an X and a Y.
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Genetic Imprinting
• A mechanism in which genes have been
modified in one of the parents and have
differing effects depending on whether they
are transmitted to the offspring through the
egg or sperm.
• An imprinted gene dominates one that has
not been imprinted.
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Polygenic Inheritance
• The genetic principle that many
genes can interact to produce a
particular characteristic.
• There are more than 50,000 genes,
imagine the possible combinations!
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Genotypes and Phenotypes
• Genotype - an individual’s genetic heritage, the
actual genetic material.
• Phenotype - the way an individual’s genotype is
expressed in observed and measurable
characteristics.
– Physical traits: height, weight, eye color
– Psychological characteristics: intelligence,
creativity, personality
• For each genotype, a range of phenotypes can be
expressed.
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Reaction Range
• Reaction range is the range of
possible phenotypes for each
genotype, suggesting the
importance of an environment’s
restrictiveness or richness.
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Canalization
• Describea the narrow path, or
developmental course, that certain
characteristics take.
• Preservative forces help protect or
buffer a person from environmental
extremes.
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Behavior Genetics
• Studies the degree and nature of behavior’s
hereditary basis.
• Assumes behaviors are jointly determined
by the interaction of heredity/environment.
• Often uses twins or adoption situations to
study the influence of heredity on behavior.
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Twin Studies
• The behavioral similarity of identical twins is
compared with those 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.
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Adoption Studies
• Investigate whether, in behavior and
psychological characteristics, adopted
children are more like their adoptive parents
(environment), or more like their biological
parents (heredity).
• Another method is to compare adoptive and
biological siblings.
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Molecular Genetics
• There is now a great deal of
enthusiasm about the use of molecular
genetics to discover the specific
locations on genes that determine an
individual’s susceptibility to many
diseases and other aspects of
health and well-being.
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Genome
• The term used to describe the complete
set of instructions for making an
organism
• Contains the master blueprint for all
cellular structures and activities for the
life span of the organism
• The human genome consists of tightly
coiled threads of DNA
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The Human Genome Project
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•
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•
Began in the 1970s
Mapping of the human genome
(30,000-35,000 genes)
Has located the genes for Huntington disease,
some forms of cancer, and many others
• May possibly be used to transplant healthy copies
of missing/defective genes into affected cells
• May lead to the development of drugs that
will alter the genetic makeup of the
affected cells
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The Collaborative Gene
• Researchers believed humans had 50,000 to
100,000 genes rather than the 30,000 to 35,000
genes found by the Human Genome Project.
• The previous belief that each gene is responsible
for the synthesis of only one protein is no longer
accepted, due to the higher number of proteins
(300,000 – 500,000) than genes.
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Chromosome and GeneLinked Abnormalities
• Chromosome
Abnormalities
– Down Syndrome
– Klinefelter
Syndrome
– Fragile X
Syndrome
– Turner Syndrome
– XYY Syndrome
• Gene-Linked
Abnormalities
– Phenylketonuria
– Sickle-Cell Anemia
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Down Syndrome
• Caused by the presence of an extra chromosome
• Characterized by:
–
–
–
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–
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round face
flattened skull
extra fold of skin over the eyelids
protruding tongue
short limbs
retardation of motor and mental abilities
• Women younger than 18 and older than 38 are
more likely to have Down syndrome babies.
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Klinefelter Syndrome
• Sex-linked chromosome abnormality
• Males have an extra X chromosome,
making them XXY instead of XY
• Characterized by:
– undeveloped testes
– enlarged breasts
– become quite tall
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Fragile X Syndrome
• Sex-linked chromosome abnormality
• The X chromosome becomes constricted
and often breaks
• Characterized by:
– mental deficiency (varied in form from mental
retardation to short attention span)
• Occurs more frequently in males
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Turner Syndrome
• Sex-linked chromosome abnormality
• Females are missing an X chromosome,
making them XO instead of XX
• Characterized by:
–
–
–
–
shortness of stature
webbed neck
possible mental retardation
possible sexual underdevelopment
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XYY Syndrome
• Sex-chromosome linked abnormality
• The male has an extra Y chromosome
• Early belief surrounding the syndrome was
that the extra Y chromosome contributed to
male aggression and violence.
• Researchers have since found that XYY
males are no more likely to commit crimes
than are XY males.
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Phenylketonuria
• Gene-linked abnormality
• The individual cannot properly metabolize
an amino acid
• Currently easily detected
• Treated by diet to prevent an excess
accumulation of phenylalanine.
• If left untreated it can result in mental
retardation and hyperactivity.
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Sickle-Cell Anemia
• Gene-linked abnormality
• Occurs most often in African Americans
• Affects the shape of red blood cells,
hindering their ability to carry oxygen to
the body’s cells
• Results in anemia and early death
of the individual
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Other Genetic Abnormalities
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•
•
•
•
•
•
Cystic Fibrosis
Diabetes
Hemophilia
Huntington Disease
Phenylketonuria (PKU)
Sickle-cell anemia
Spina Bifida
Tay-Sachs Disease
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Reproduction Challenges
and Choices
Prenatal
Diagnostic
Tests
Infertility
Adoption
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Prenatal Diagnostic Tests
• Amniocentesis
• Ultrasound Sonography
• Chorionic Villi Sampling
• Maternal Blood Test
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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)
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Ultrasound Sonography
• A prenatal medical procedure in which high
frequency sound waves are directed into the
pregnant woman’s abdomen
• Echo from the sounds is transformed into a
visual representation of the fetus’s
inner
structures
• Able to detect such disorders as
microencephaly
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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
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Maternal Blood Test
• Called the alpha-fetoprotein (AFP) test
• A prenatal diagnostic technique used to
asses blood alphaprotein level, which is
associated with neural-tube defects
• Administered between the 14th and 20th
weeks of pregnancy
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Infertility
• Infertility is the inability to
conceive a child after 12
months of regular intercourse
• Approximately 10-12% of
couples in the U.S. experience
infertility.
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Causes of Infertility
• Women
– Ovulation
problems
– Antisperm
secretions
– Blocked
fallopian tubes
– Endometriosis
• Men
– Low sperm count
– Immobile sperm
– Antibodies
against sperm
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Infertility Treatment Techniques
• In vitro fertilization (IVF)
(Success rate < 20%)
• Gamete intrafallopian transfer (GIFT)
(Success rate ~ 30%)
• Intrauterine insemination (IUI)
(Success rate 10%)
• Zygote intrafallopian transfer (ZIFT)
(Success rate ~ 25%)
• Intracytoplasmic sperm injection (ICSI)
(Success rate ~ 25%)
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Adoption
• Adoption is the social and legal
process by which a parent-child
relationship is established
between persons unrelated at
birth.
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Research Findings on
Adoption
• Adopted children and adolescents often show
more psychological and school-related problems
than non-adopted children.
• Adopted adolescents are referred to psychological
treatment 2-5 times as often as their non-adopted
peers.
• Early adoption often has better child outcomes
than later adoption.
• Adoptees show higher levels of prosocial behavior
than non-adopted peers.
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Adoption Related Issues
• Research findings have implications for social
policy regarding the foster care system.
• Clinical psychologists report that sometimes
adoptive parents try to make life too perfect for
adoptive children, and thus the children feel that
they can’t release any angry feelings or openly
discuss problems.
• Consensus among psychologists is that adopted
children should be told they are adopted.
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Heredity - Environment
Interaction
Intelligence
Heredity-Environment
Correlations
Shared and Nonshared
Environmental
Experiences
Conclusions about
Heredity-Environment
Interaction
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Intelligence
• Jensen theorizing that intelligence is primarily inherited.
• Believed that standardized IQ tests are a good indicator of
intelligence.
• Supported his theory with findings from twin studies:
IQs of identical twins yielded an average correlation of .82
IQs of ordinary siblings yielded an average correlation of .50
IQs of identical twins reared together yielded a correlation of .89
IQs of identical twins reared apart yielded a correlation of .78
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Criticisms of Jensen’s Work
• IQ tests tap only a narrow range of intelligence,
excluding important aspects such as everyday
problem solving, work, and social adaptability.
• Most investigations of heredity and environment
don’t include environments that differ radically.
• Developmentalists believe intelligence is
influenced by heredity, but such a strong
relationship has not been found.
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The Bell Curve: Intelligence and
Class Structure in Modern Life
• Highly controversial book written in 1994 by
Richard Herrnstein and Charles Murray.
• States IQ test scores vary across ethnic groups:
– Asian Americans score several points higher
than Whites.
– African Americans score about 15 points lower
than Whites.
• IQ differences are partly due to heredity.
• Believes government funding for projects such as
Head Start is wasted.
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Criticisms of The Bell Curve
• While experts agree that African Americans
tend to score lower on IQ tests, they
question the ability of the tests to accurately
measure intelligence.
• The U.S. Supreme Court endorsed this
criticism by ruling that tests of general
intelligence are discriminatory and cannot
be used for determining employment.
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Heredity-Environment
Correlations
• The concept that individuals’ genes
influence the types of environments to
which they are exposed.
• Behavior-geneticist Sandra Scarr described
three ways that heredity and environment
are correlated:
– Passively
– Evocatively
– Actively
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Passive GenotypeEnvironment Correlations
• Occur when biological parents, who are
genetically related to the child, provide a
rearing environment for the child.
• Example:
– Parents who have a genetic predisposition to be
intelligent and read skillfully, provide their
children with books to read. The children, in
turn, become skilled readers due to both their
inherited predispositions and environmental
influences.
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Evocative GenotypeEnvironment Correlations
• Occur because a child’s genotype elicits
certain types of physical and social
environments.
• Examples:
– Active, smiling children receive more social
stimulation than passive, quiet children do.
– Athletically inclined youth tend to elicit
encouragement to engage in school sports.
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Active (Niche-Picking) GenotypeEnvironment Correlations
• Occur when children and adolescents seek out
environments they find compatible and
stimulating.
• Niche-picking refers to finding a setting that is
suited to one’s abilities.
• Active selection of environments is related to
one’s genotype.
• Example:
– Teens who are musically inclined select musical
environments in which they can successfully perform
their skills.
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Shared and Nonshared
Environmental Experiences
• Children living under the same roof
with the same parents, often have very
different personalities.
• Robert Plomin found that common
rearing, or shared environment,
accounts for little of the variation in
children’s personality or interests.
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Shared Environmental
Experiences
• Children’s common experiences:
– parents’ personalities and intellectual
orientation
– family’s social class
– neighborhood in which they live
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Nonshared Environmental
Experiences
• Children’s unique experiences, both within
the family and outside the family, that are
not shared with another sibling.
• Experiences occurring within the family can
be part of the “nonshared environment.”
• Parents often interact differently with each
sibling, and siblings interact differently with
parents.
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Conclusions about HeredityEnvironment Interaction
• Both genes and environment are necessary for a
person to exist.
• Heredity and environment operate together, or
cooperate, to produce:
– intelligence
– temperament
– height
-weight
-ability to pitch a baseball
-ability to read
• The emerging view is that genes give people a
propensity for a particular developmental
trajectory that is ultimately realized through
environmental circumstances.