Transcript Behavior Genetics and Evolutionary Psychology

BEHAVIOR GENETICS
AND EVOLUTIONARY
PSYCHOLOGY
Module
11
BEHAVIOR GENETICS
Behavior Geneticists: researchers who
study our differences and weigh the
effects and interplay of heredity and
environment.
Environment – every non-genetic
influence, from pre-natal nutrition to the
people and things around us
GENES: OUR CODES FOR LIFE
 46 chromosomes – 23 from each parent
 Chromosomes – threadlike structures made of DNA
molecules that contain the genes
 DNA – a complex molecule containing the genetic
information that makes up the chromosomes.
 Genes – the biochemical units of heredity that make up
the chromosomes; segments of DNA capable of
synthesizing a protein
 Can be active(expressed) or inactive
 Turned on by environmental events (stress, diet, drugs)
 When turned on – provides the code for creating protein
molecules, our biological building blocks
 Genome – the complete instructions for making an
organism, consisting of all the genetic material in the
organism’s chromosomes
TWIN AND ADOPTION STUDIES
Identical twins – (monozygotic) develop from
a single fertilized egg that splits in two,
creating two genetically identical organisms
 Placenta difference
Fraternal twins – (dizygotic) develop from
separate fertilized eggs
Identical twins have more similar traits like
outgoingness and emotional stability
Traits affect behaviors; makes them behaviorally
more similar (ex) divorce rate
TWIN AND ADOPTION STUDIES
Separated twins: (Minnesota Twin Study)
 Similar in taste, physical attributes, personality,
abilities, attitudes, interests, fears despite different
environments = strength of genetics
 Critics: share an appearance and the response it
evokes, placed in similar homes by adoption
agencies, can fine similarities even in non-biological
pairs
Adoptee studies: more similar to biological
parents in extroversion/agreeableness
Environment has no discernable impact on their
personalities
TWIN AND ADOPTIVE STUDIES
Why are children in the same family so
different?
 Gene difference?
 Unique peer influences and life events?
 Sibling relationships ricochet off each other amplifying
their differences?
 Differing genes lead to different personalities which
evoke different responses in parents?
Parental influence: attitudes, values, manners,
faith, & politics
Adoption beneficial: parents screened
TEMPERAMENT AND HEREDIT Y
Temperament – a person’s characteristic
emotional reactivity and intensity
Present at birth
Biologically rooted and environmentally
influenced
 Variable heart rates, reactive nervous systems
 (ex)Gene that regulates neurotransmitter serotonin
which predisposes child to have a fearful
temperament. Mix that with an unsupportive
caregiver = inhibited child
MOLECULAR GENETICS
Subfield in biology that studies the molecular
structure and function of genes
Goal is to find some of the many genes that
together orchestrate traits such as body weight,
sexual orientation, and extraversion.
Purpose is to predict risk factors so steps can be
taken to prevent problems before they happen
Find families with disorders across generations
and compare DNA of those within a family that
have the disorder with those that do not
Research can lead to finding potential problems
in fetuses
 Controversial - Labeling, discrimination, abortions
HERITABILIT Y
The proportion of variation among individuals
that we can attribute to genes (how much
differences among people are attributable to
genes)
As environments become more similar,
heritability increases
As environments differ, heritability decreases
GENE-ENVIRONMENT INTERACTION
NATURE VIA NURTURE
 Most important human similarity is our enormous
adaptive capacity
 Interaction – the interplay that occurs when the
effect of one factor (such as environment) depends
on another factor (such as heredity)
 Epigenetics – the study of influences on gene
expressions that occur without a DNA change
(studying the molecular mechanisms by which
environments trigger genetic expression)
 Epigenetic mark – organic methyl molecules attracted
to part of a DNA strand
 It instructs the cell to ignore any gene present in the DNA
stretch, thereby preventing the DNA from producing the
protein coded by that gene.
 Triggered by diet, drugs, stress
EVOLUTIONARY PSYCHOLOGY
Studies how natural selection has
shaped our traits and behavior
tendencies.
Variations increasing the odds of reproducing
and surviving are most likely to be passed on
Other variations arise from:
Mutations – a random error in gene
replication that leads to a change
New gene combinations at conception
EVOLUTIONARY SUCCESS HELPS EXPLAIN
SIMILARITIES
 Our behavioral and biological similarities arise
from our shared human genome
 We are more similar than we are different
 More variation within a group of people than
between a group of people
 Similarities a result of natural selection – we
have the traits that enable survival and
reproduction
 Mismatched with today’s environments
 Irrational fears – spiders, snakes, airplanes over guns
and electricity
 Explains stranger anxiety, parental protection of
children
EVOLUTIONARY EXPLANATION OF HUMAN
SEXUALIT Y
 Gender – in psychology, the biologically and socially
influenced characteristics by which people define
male and female
 Different sexual views/behaviors
 Goal to pass on genes
 Women can’t reproduce as quickly as men – must incubate
fetus
 Attracted to mature, affluent, dominant men(ability to
support and protect)
 Men can spread seed quickly
 Attracted to youthful women and with waists a third smaller
than hips (fertile)
 Women pair wisely, men pair widely
CRITICISMS OF EVOLUTIONARY THEORY
Hindsight explanation – look at effect and
assume cause
Reinforces stereotypes of each gender –
rationalizes behaviors
Ignores cultural influences and perceptions
Male/female behaviors may be result of
environment not pre-wired
Doesn’t explain the relatively quick
changes in sexual behaviors and views