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Unit 3: Biological Psychology

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Title: Unit 3: Biological Psychology


1
Unit 3 Biological Psychology
  • Essential Task 3-8
  • Explain how heredity and environment work
    together to shape behavior with specific
    attention to hereditability and gene-environment
    interaction.

2
We are here
3
Essential Task 3-8
Outline
  • Explain how heredity and environment work
    together to shape behavior with specific
    attention
  • Genes 101
  • Twins and Adoption
  • Hereditability vs. Environmentability
  • Strain Studies and Selection Studies
  • Gene-environment interaction

4
Behavior Genetics Predicting Individual
Differences
Behavior Geneticists study our differences and
weigh the relative effects of heredity and
environment or NATURE vs. NURTURE
5
Genes Our Codes for Life
Chromosomes containing DNA (deoxyribonucleic
acid) are situated in the nucleus of a cell.
6
Genes Our Codes for Life
Segments within DNA consist of genes that make
proteins to determine our development.
7
Genome
Genome is the set of complete instructions for
making an organism, containing all the genes in
that organism. Thus, the human genome makes us
human, and the genome for drosophila makes it a
common house fly.
8
Genes 101
  • Dominant Gene Member of a gene pair that
    controls the appearance of a certain trait.
  • Recessive Gene - Member of a gene pair that
    controls the appearance of a certain trait only
    if it is with another recessive gene.

9
Genes 101 contd
  • Polygenic Inheritance Process by which several
    genes interact to produce a certain trait
    responsible for our most important traits.

10
Twin Biology
Studying the effects of heredity and environment
on two sets of twins, identical and fraternal,
has come in handy.
11
Mz vs. Dz Twins
  • The odds of having identical twins is about 3 in
    1,000, whereas the birthrate for all twins is
    about 32.2 in 1,000.
  • Most (6070) monozygotic twins share the same
    placenta but have separate amniotic sacs.
  • A small number (1-2) of monozygotic twins share
    the same placenta and amniotic sac.
  • Fraternal twins each have their own placenta and
    own amniotic sac.

12
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13
Separated Twins
A number of studies compared identical twins
raised separately from birth, or close
thereafter, and found numerous similarities.
Separated Twins
Personality, Intelligence
Abilities, Attitudes
Interests, Fears
Brain Waves, Heart Rate
14
Jim Lewis
  • Middle Class
  • Wife named Betty left her love notes
  • Son named James Alan
  • Dog named Toy
  • Woodworking hobby
  • Circular white bench around a tree in his yard.
  • Chain Smoker
  • Bit his fingernails
  • Drove a Chevy, watched stock car racing, and
    drank Miller-Lite
  • Suffered from High Blood Pressure and Migraines

15
Jim Springer
  • Calls his 37 year separated twin in February 1980
  • Everything down to the dogs name is the same
    (except sons James Allan vs. James Alan)
  • When played their voices, they would mistake
    themselves for their twin
  • They are the first in Thomas Bouchards twin
    study
  • Studied 80 pairs of identical twins reared apart

16
Separated Twins
Critics of separated twin studies note that such
similarities can be found between strangers. Let
us see if they might be correct but
Researchers point out that differences between
fraternal twins are greater than identical twins.
17
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18
Adoption Studies
Adoption studies, as opposed to twin studies,
suggest that adoptees (who are biologically
unrelated) tend to be more different from their
adoptive parents and siblings than their
biological parents.
19
Where is the environment?
  • Adoptees bear more resemblance in their
    outgoingness and agreeableness to their
    biological parents then to their adopted parents
  • Two adopted children in the same home bear no
    more resemblance to each other than kids from two
    separate families.

20
Adoptive Studies
Adoptive studies strongly point to the simple
fact that biologically related children turn out
to be different in a family. So investigators ask
Why are children in the same family so different?
Do siblings have VASTLY differing experiences?
Do siblings, despite sharing half of their genes,
have different combinations of the other half of
their genes?
Ultimate question Does parenting have an effect?
21
Parenting
Parenting does have an effect on biologically
related and unrelated children.
Parenting Influences childrens
Attitudes, Values
Manners, Beliefs
Faith, Politics
Mom may be holding a full house while Dad has a
straight flush, yet when junior gets a random
half of each of their cards his poker hand may be
a loser. David Lykken (2001)
22
Heritability
Heritability refers to the extent to which the
differences among people are attributable to
genes.
What percentage of the difference among peoples
height can be attributed to their genes?
90
23
Heritability
  • Because heritability is a proportion, its
    numerical value will range from 0.0 (genes do not
    contribute at all to phenotypic individual
    differences) to 1.0 (genes are the only reason
    for individual differences).
  • For human behavior, almost all estimates of
    heritability are in the moderate range of .30 to
    .60.

24
Environmentability is the opposite
  • It is the extent to which the differences among
    people are attributable to the environment.
  • If the heritability of most human behaviors is in
    the range of .30 to .60, then the
    environmentability of most human behaviors will
    be in the range of .40 to .70.

25
What can you say?
  • Heritability and environmentability are
    population concepts. They tell us nothing about
    an individual
  • A heritability of .40 informs us that, on
    average, about 40 of the individual differences
    that we observe in, say, shyness may in some way
    be attributable to genetic individual difference.
  • It does NOT mean that 40 of any person's shyness
    is due to his/her genes and the other 60 is due
    to his/her environment.

26
Animal behavior genetic studies include
  • Strain studies
  • Intense inbreeding over the course of many
    generations creates a genetically similar strain.
  • Two or more strains are raised at once to
    determine the extent to which the differences
    among the two groups are attributable to genes
    (hereditability)

Compare the differences
27
Animal behavior genetic studies include
  • Selection Studies
  • If a trait is closely regulated by genes then if
    animals with trait are interbred with those that
    dont, more of their offspring should have the
    trait then in a normal population

28
Nature and Nurture
Some human traits are fixed, such as having two
eyes. However, most psychological traits are
liable to change with environmental experience.
Genes provide choices for the organism to change
its form or traits when environmental variables
change. Therefore, genes are pliable.
29
Gene-Environment Interaction
Genes can influence traits which affect
responses, and environment can affect gene
activity.
A genetic predisposition that makes a child
restless and hyperactive evokes an angry response
from his parents. A stressful environment can
trigger genes to manufacture neurotransmitters
leading to depression.
30
Gene-Environment Interaction
Genes and environment affect our traits
individually, but more important are their
interactive effects.
Rex Features
People respond differently to Rowan Atkinson (Mr.
Bean) than Orlando bloom.
31
Not Nature vs. Nurture
  • Gene-Environment Interaction is Nature AND Nurture

32
Gene-environment correlation
  • Passive - Bio-Parents directly pass on genes to
    their kids. But Bio-Parents also pass on home
    environments that are influenced by their
    own heritable characteristics.
  • Evocative (or reactive) gene-environment
    correlation happens when an individual's genetic
    makeup evokes an environmental response.
  • Active gene-environment correlation occurs when
    an individual possesses a heritable propensity to
    select environmental exposure. For example,
    individuals who are extroverted may seek out very
    different social environments than those who are
    shy and withdrawn.
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