The Psychology of the Person Chapter 10 Biological Research

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The Psychology of the PersonChapter 10
Biological Research

• Naomi Wagner, Ph.D
• Lecture Outlines
• Based on Burger, 8th edition

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Heritability of personality traitsHuman traits
are Polygenic

• More and more evidence is accumulating in support
  of the heritability of our traits and our
  aptitudes. How do we separate environmental from
  genetic effects?
• The twin study method. Identical (monozygotic)
  twins (MZ) share 100 of their genes. They are
  compared to fraternal (dizygotic) twins (DZ), who
  share Apr. 50 of their genes. When given a
  variety of personality tests, MZ twins scores
  are much more similar to each other than DZ
  twins scores.

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Identical twins share 100 of their genes

• They are formed when a fertilized egg (zygote) is
  split , forming two identical zygotes

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Fraternal twins share about 50 of their genes

• They are formed when two different eggs are
  fertilized by two different sperm cells

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Other Methods to Study Heritability

• Please note that the heritability of many
  psychiatric disorders has been established
• Human characteristics are polygenetic, establish
  by more than one gene, a fact which affects the
  study of heritability
• Other procedures compare adopted children to
  their biological parents and adoptive parents,
  finding more similarities between the adopted
  children and their biological parents.

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Heritability (cont-d)

• Also, studies comparing MZ twins raised together
  vs. MZ twins raised apart find that the identical
  twins raised apart are quite similar to each
  other, as much as identical twins raised
  together, suggesting a strong genetic influence
  on personality.
• In response, some critics suggest that identical
  twins may experience more shared environment
  than fraternal twins, but this type of argument
  is rather weak.

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Introverts are NOT Shy

• They try to control their level of arousal

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The study of extraversion-introversion

• The genetic basis for this dimension has been
  supported by large-scale twin studies in Sweden
  and Finland.
• Physiologically, introversion has been
  associated with high sensitivity to stimulation
• A study in libraries found that introverted
  people preferred scheduled area to study in,
  while extraverted preferred open, noisy areas.
• This study supported the hypothesis of
  sensitivity to stimulation.

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Who is Happier?

• Are extraverted people happier than introverted?
  Extraverted people experience higher levels of
  positive affect than introverted.
• Maybe because they have more friends, and also
  they may be more sensitive than introverts to
  information about rewards.

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(cont-d)

• Regarding happiness, researchers look at
  happiness in terms of subjective well being,
  which can be divided into positive and negative
  affect.
• Happiness is obtained by increasing positive
  affect and decreasing negative affect.
• Though extraverts experience more positive affect
  than introverts, they are also more impulsive, a
  factor that may get them into trouble. They may
  experience more mood swings than introverted.

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Evolutionary Theory and Mate selection

• Evolutionary psychology is interested in
  understanding the biological basis for human
  behavior.
• Current human traits and attributes are seen as
  evolving in us because they were useful for our
  survival in our prehistoric past.
• The purpose of life is seen as the survival of
  the species, the transmission of our genes to the
  next generation.

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Parental Investment

• Because of biological differences (the cheap
  sperm and precious egg), men and women have
  different parental investments in the
  transmission of their genes to their offspring,
  and that is why they have evolved differently in
  terms of mate selection.
• Note lonely hearts studies. How do men and
  women market themselves in order to attract a
  mate, and what are theyre looking for in a
  potential partner?

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Gender Differences in Mate Selection

• Men prefer youth and beauty, because these
  indirectly mean health and fertility.
• Women prefer ambition, resources in a man.
• Since their parental investment is larger than
  the mans, they contribute their precious egg,
  women need to guarantee (not in the personal
  sense, but in the sense of the species) that
  their relatively few offspring will be protected
  while they gestate, give birth, and nurse.
• Note cross-cultural studies showing that men in
  different cultures all over the world prefer
  youth and beauty in a mate.

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He wants youth and beauty she wants resources

• She has youth and beauty he has money