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The Genetics of Behavior
Are we nature or
nurture?
Two basic views
Nativists Emphasize genes and inborn characteristics
Empiricists
Emphasize learning and experience
Evolutionary Psychology
Emphasizes
evolutionary mechanisms
that may help explain human
commonalities in;
Cognition,
development, emotion, social
practices and other behavior.
Behavioral Genetics
An
interdisciplinary field of study
concerned with the genetic basis of
behavior and personality.
An Understanding
All
scientists understand there is an
interaction between heredity and
environment.
Set point - a genetically influenced
weight control mechanism vs. obesity
in the US.
The Secrets of Genes
Genes
- are the basic units of heredity
located on chromosomes which contain
threadlike strands of DNA.
Egg and Sperm contain 23 chromosomes
each.
Creating the genome
Genome and what it means
After
conception each cell has 23
pairs of chromosomes. (46)
Most traits depend on more than one
gene pair.
How are traits studied?
Linkage
studies - look for patterns of
inheritance of genetic markers in
large families.
A genetic marker is a segment of
DNA that varies among individuals.
The Genetics of Similarity
Evolution
is a change in gene
frequencies within a population over
many generations. (mutation)
Natural Selection is a process in
which individuals adapt to a particular
environment and survive.
Evolutionary Psychologists
They
look to the prehistoric record
to draw inferences about behavior
that solved survival problems
Because of evolutionary history some
qualities are universal…
Evolutionary Psychologists

Universal qualities are.
1.
2.
3.
4.
5.
Reflexes
Attraction to novelty
A desire to explore and manipulate
objects
An impulse to play and fool around
Basic mental skills
Our Human Heritage

The origins of perception
1.
2.
Sensation - the detection of physical
energy emitted or reflected by
physical objects.
Perception - the process by which the
brain organizes and interprets sensory
information
Our Human Heritage
3.
4.
5.
Some abilities develop from certain
experiences at certain times.
Complex features are processed by
specialized detectors
Inborn perceptual abilities include…
1.
2.
Startle reflex
Audio location
3. Voice recognition
4. Discrimination of smells
The Face of Emotion
Some
expressions are universal and
present from birth
Universal
facial expressions function
in communication.
Sociability and Attachment
Synchrony
and sociability
Newborns are sociable from birth
They pay attention to human faces
show synchrony
Attachment
and
- the emotional tie that
children and their caregivers feel
toward each other…
Sociability and Attachment
Attachments
Contact
cont’d
comfort which is the innate
pleasure derived from close physical
contact.
Infants who do not develop secure
attachments may develop emotional and
physical problems.
The Capacity for Language
Language
is a system for combining
meaningless elements into utterances
that convey meaning.
A
child’s vocabulary increases at a rapid
rate.
Language Development
Requires
the mastering of a complex
set of rules including:
Surface
structure - the way a sentence
is actually spoken
Deep structure - the meaning inferred
by a sentence
Syntax - the rules of grammar
Language Development
Children
They
do not simply imitate adults
are able to perceive deep
structure
Noam Chomsky theorized that we have a
biologically based “language acquisition
device” that aids in language
development.
Chomsky’s Examples

Children of
different cultures
go through similar
stages of
linguistic
development


Children combine
words in ways that
adults never would
Adults do not
consistently correct
their children’s
syntax yet they learn
to speak or sign
correctly.
Chomsky’s Examples
Even
children who
are profoundly
retarded acquire
language.
Infants
as young as
7 months can
derive simple
linguistic rules
from a string of
sounds.
Does Nurture Play a Role?
Imitation
does play a role because
parents correct the child’s
ungrammatical sentence.
There appears to be a window of
opportunity to learn language.
Evolution, Courtship and Mating
Sociobiology
- an interdisciplinary field
that emphasizes evolutionary explanations
of social behavior in animals.
The view is that nature has selected
psychological traits and social customs that
promote propagation.
Evolution, Courtship, and
Mating
Sociobiologists
argue that males and
females have evolved different mating
strategies.
Males
to inseminate as many females as
possible and females be more selective.
As a result, males are thought to be more
promiscuous and drawn to sexual novelty,
females are more interested in stability.
Sociobiology vs. Evolutionary
Sociobiologists
tend to argue by analogy to
nonhuman animals. Evolutionary biologists
recognize these are simplistic and
misleading.
Critics argue that evolutionary
explanations are based on stereotype of
gender. Theories are also nonfalsifiable.
The Genetics of Difference
Heritability
- is the statistical
estimate of the proportion of the
total variance in some trait that is
attributable to genetic differences
among individuals within the group…
The Genetics of Difference
1.
2.
3.
An estimate of heritability applies only to
a particular group living in an particular
environment.
Heritability estimates do not apply to
individuals, only to variations within a
group.
Even highly heritable traits can be
modified by the environment.
Computing Heritability
Research
methods are used in an
attempt to infer heritability by
studying people whose degree of
genetic similarity is know.
Adopted
children share half their genes
but not environments with birth parents.
Computing Heritability
Identical
(monozygotic) twins develop when a
fertilized egg divides into two parts.
Fraternal (dizygotic) twins develop from two
separate eggs fertilized by different sperm.
Identical twins raised apart from each other
are of special interest because they have
identical genes but a different environment.
Heritability and Intelligence
Intelligence
quotient (IQ) - is a
measure of intelligence originally
computed by dividing a person’s
mental age by his or her chronological
age multiplied by 100
Currently it is norms based.
Genes and Individual
Differences
 IQ
scores are highly heritable with estimates
averaging around .50 in children and .60 to .80 in
adults.
 Scores of identical twins are always more highly
correlated than those of fraternal twins.
 Scores with adopted children correlate higher
with birth parents vs. adoptive parents.
The Question of Group
Difference
Race
differences are controversial
Asians
as a group score higher than
whites who score higher than African
Americans.
Some theorists have confused intragroup findings with inter-group.
The Question of Group
Difference
Minority
children tend to have access to
fewer educational and material
resources.
Well designed studies have failed to
reveal genetic differences.
Genes and Personality
Temperaments
- physiological
dispositions to respond to the
environment in certain ways; present
in infancy and are assumed to be
innate.
Heredity and Temperament
Differences
in children’s
temperaments appear early in
childhood.
Temperaments tend to remain stable
throughout childhood.
Heredity and Traits

A
trait analysis
isof
a characteristic
measures
or scores
of an
that
Clusters
Factor
- a statistical
method
are
individual,
highly correlated
describing
aare
habitual
assumed
wayto
for analyzing
the inter-correlations
of
measure
behaving,
the thinking
samemeasures
underlying
and feeling.
trait or
among
different
now
ability.
applied to traits.
Big Five Factors
Introversion
vs. extroversion
Neuroticism or negative emotionality
Agreeableness
Conscientiousness
openness
Why are genes not everything?
Not
all traits are equally heritable or
unaffected by shared environments
Some studies may underestimate the
impact of the environment
Even traits that are highly heritable are
not rigidly fixed and can be modified by
experience.