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					The Nature and Nurture
     of Behaviour

       Myers in Modules, Module 5
           Module 5
Genetic Influences on Behavior

          Myers in Modules, Module 5
What makes you…
There are shared factors within the human race:
i.      Preference for sweets and fatty foods
ii.     Similar physical traits
iii.    Similar behavioural traits
iv.     Divide colour spectrum the same way
v.      Attracted by behaviours that protect offspring
vi.     Attracted by female youth and vigor features
vii.    Fear strangers by age 8 years
viii. We socialize; conform; organize; punish;
affiliate; dance; love; procreate; sing; worship, etc,

                    Myers in Modules, Module 5
What makes you…
There are individual factors which are unique to you:
i.    Intelligence
ii.   Happy and content
iii.  Aggressive or tolerant
iv.   Gay or straight
v.    Artistic or logistically inclined
vi.   Thin or thick
vii.  Conceal or repress anger
viii. Independent or conformist
ix.   Academic or practically inclined, etc.

                    Myers in Modules, Module 5
Genes: Our Biological Blueprint

           Myers in Modules, Module 5
Chromosomes: 23 pairs (one set from mother ; one
from father.) Total = 46

DNA molecule (deoxyribonucleic acid) form double
spiral structures

Genes: Our biological blueprint made of segments
of DNA which control protein formation.

Nucleotides: four proteins, in two pairs: (A-T)
Adenosine - Tyrosine, and (C-G) Cytosine –

Gene Complexes: Genetic information which are
determined by the sequence of several pairs of
nucleotides. This sequence directs the cell to
produce selected proteins. Module 5
                  Myers in Modules,
Genes: Their Location and Composition

             Myers in Modules, Module 5
 Evolutionary Psychology: Explaining
         Universal Behaviors
Selective breeding:
  i. Dmitry Belyaev, Russian Academy of
      Sciences took wild foxes, bred them
      and selected 5% of males and 20% of
      females for docility.
  ii. 40 years and 45,00 foxes later, new
      strain of completely domesticated
  iii.Indicates the powerful method which
      Nature uses to select for adaptive and
      useful traits.

                Myers in Modules, Module 5
Natural Selection
• Nature selects traits based on survival and ability to reproduce.
• Organisms with inferior traits to both less well and over time these
  traits are decreased in frequency in the population
• Examples: Moose antlers, A-B resistant bacteria, peppered moth
  in Britain

Differences in humans:
   6% are differences among races
   8% are differences among groups within a race (West Indians vs.
   85% are differences (genetic variation within the groups)

• Genetic differences (variation) between two Kenyans or two
  Icelanders, is greater than the average difference between their
  respective groups. Result: If only one race survived a global
  catastrophe, an insignificant loss of genetic diversity would occur.

                        Myers in Modules, Module 5
Evolutionary Psychologists deal with questions
    such as :
   Why do infants fear strangers, at the same time they
    become mobile?
   Why are biological fathers less likely to abuse their
    children than un-related boyfriends living in the same
   Why are parents so devoted to their children?
   Why are there more phobias about spiders and
    snakes than guns and airplanes?
   How and Why do men differ from women?
    in perceiving friendliness as sexual interest;
    in initiating sexual relations;
    in feeling jealous rage over infidelity with their mate.

                      Myers in Modules, Module 5
– Video store customers N=2350 M= 80%; F= 20%
  (50% Ms say they watch with partner)
– College students agree with sex following short term
  friendly aquaintences N=281,064; M=55%; F= 32%
– 18-59 year olds requiring affection for partner as
  necessary prior to sex (N=3432; M=25%; F= 48%)
– Think about sex every day N=3432; M= 54%;
– Florida State U. Hit on members of opposite sex
  with suggestion to “go to bed” (Agreed: M=75%;
  F= 0%)
– Attribute friendliness as a sexual interest. Men,
  much more often than women, Helps explain greater
  assertiveness by males, and confusion on intent.
                Myers in Modules, Module 5
  An Evolutionary Explanation from our
   primitive past.

Female investment in time and effort for
 reproduction guides them to find good
 providers and protectors desirable.
Males have a little investment in time and
 effort and great ability to reproduce many
 offspring. They look for females with long-
 term reproductive potential in health, vigor,
 childbearing shape, child nursing capability.

                Myers in Modules, Module 5
      A Study of Worldwide Mating Preferences

N=10,047 , 37 countries: Men prefer women with physical attractiveness
(suggesting youth and health). Women prefer men with resources, power,
health and social status.
                           Myers in Modules, Module 5
A Critique of the Evolutionary Explanation
Other mechanisms contrary to this interpretation exist and can be accepted as adaptive:
i.     Should not children of supportive fathers more often survived to perpetuate genes?
ii.    Might not men secure greater contributions to the gene pool by monogamy to protect kids
       and to prevent other male intrusions.
iii.   Are bonobos (African monkeys) non-adaptive with their promiscuous females?

  Much of our behaviour is NOT hardwired:
  Men socialized in committed family environments may not seek sexual trysts,
  whereas females with examples of social values accepting casual sex may well
  adopt these values as well.
  Gender differences in preferred traits for mates in traditional societies with gender
  inequality (home maker mother) are not found in societies which have widespread
  gender equalities (if you can find them)

  Genetic determinism suggested by these Evolutionary Approaches to
  psychology may impede progression towards more progressive social change.

  Evolutionary Psychologists point to the rigor and power of evolutionary
  mechanisms in all living creatures and the obvious influence of genetic similarities
  in behaviour within species.

                                  Myers in Modules, Module 5
          Behavior Genetics:
    Explaining Individual Differences
Twin Studies
Identical twins (almost 100% same genes)
 Increased divorce rates in fraternal twin is 1.6X if
   other twin does
 Increased divorce rates in identical twin is 5.5X if
   other twin divorces.
Fraternal twins (different genes as other sibs)
 Surveys of 850 pairs indicated Identical twins have
   much more in common than Fraternal twins, but the
   former were often treated much more similarly… as
   one individual.
Separated twins
• Adoption Studies Myers in Modules, Module 5
Myers in Modules, Module 5
           Behavior Genetics:
     Explaining Individual Differences
Twin Studies
• Separated twins (examples: p. 106)
  i.   Striking similarities in behaviour and choices of
  spouse, careers, preferences, even name of dog.
  ii. Studies with 70,000 twin pairs; 99 separated twins;
  200 separated fraternal twins. Identical twins living
  together had more personality traits in common than
  separated twins, who were more similar than fraternal
  twins either together or separated.
• Adoption Studies (examples: p.107-108) Adoptees’
  personalities and behaviour more resemble biological
  parents rather than adopted parents.
  Adoptees do benefit from adoption. They are likely to
                       IQ in Modules, Module 5
  exceed parents on Myerstests (enriched environments?)
           Behavior Genetics:
     Explaining Individual Differences
Twin Studies
• Temperament Studies (examples: p. 109)
  i.   Infant’s temperament is reported by parents as
  having striking differences in some siblings.
  ii. “Difficult” babies are more irritable, intense,
  unpredictable; “easy” babies are more relaxed, cheerful
  and predictable in later life.
  iii. emotional reactivity, reactions to change, inhibitions
  and fearful traits in newborns and toddlers continue in
  older kids.
  iv. Physiological traits of higher BP, pulse rate and
  reactive nervous systems are known from emotional
                      Myers in Modules, Module 5
           Behavior Genetics:
     Explaining Individual Differences
Twin Studies
• Heritability (examples: p. 109)
  i.    The term refers to the extent to which genetic factors
  influence a trait or behaviour. More accurately, it is the
  proportion of the variation amongst groups of individuals,
  which can be attributed to the individual’s genes.
  ii. It is NOT the amount that this trait is influenced by
  genes in any one individual. So we can’t say “My
  intelligence is 50% genetic”
  iii. If environmental factors are kept the same, the
  differences in the traits of two individuals should be
  influenced more by the only other variable which is
  different….their genes.
                      Myers in Modules, Module 5
              Behavior Genetics:
        Explaining Individual Differences
Twin Studies
• Group Differences: (p. 110)
  i.  Although we can help explain differences in the
      behavioural traits of individuals in terms of their genetic
      make-up; the same is NOT true for groups.
  ii. Although differences in height are heritable, group
      differences in height increase in the past few decades in
      North America are due to improved nutrition.
• Nature enables Nurture
  i.  Eating disorders have a genetic influence, but social norms
      for thinner people and reduced family structure and support
      produced the emotional precursors.
  ii. Criminal and aggressive tendencies have genetic
      influences, however, social influences caused the
      explosion of juvenile violence in the 1980’s, and it’s
                      Myers in the late 90’s.
      subsequent decline inModules, Module 5
           Behavior Genetics:
     Explaining Individual Differences
Gene Environmental Interaction
• Interactivity of expression (examples: p. 111)
  i.   Genes and environment don’t independently
       contribute to personality and behaviour….they
       interact to do so!
  ii. A genetically aggressive child may be yelled at and
       punished, which produces resentment &
  iii. This explains why twin separated at birth both recall
       parental warmth and support as remarkably
       similar….they generated this response with their
       similar personalities.
  iv. We are a product of a cascade of interactions
       between our genetic predispositions and the reactive
                      Myers in Modules, Module 5
           Behavior Genetics:
     Explaining Individual Differences
Molecular Genetics
• Specific gene /behaviour links (examples: p. 111-112)
  i.   There are probably a number of genes which affect
       obesity such as those for: appetite, sensation of
       fullness, metabolism, number of fat cells, level of
       activity, etc.
  ii. The role of Molecular Genetics is to determine what
       and where these genes are on the chromosomes and
       how and why they are expressed in individuals.
  iii. Method includes: draw blood, sequence the DNA,
       look for differences between groups having an
       affliction or not.
  iv. These tests enable verification of genetic disorders
       such as bi-polar disorder and predicting the genetic
                       Myers in Modules, Module 5
       risk of it occurring in young from parental sampling.

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