Transcript The Biological Tradition: The Nature versus Nurture

The Biological Tradition
• Examples from lecture on history:
• The 4 humors (Melancholic, Sanguine)
• Phrenology
• Body Types
The Biological Tradition
Phineas Gage (1823-1860)
Temperament
• Individual differences in general mood
or quality of emotional response that are
moderately stable, inherited, and
biologically based
Inhibited versus Uninhibited Children
(Kagan, 1994)
• Inhibited
– Reacts to unfamiliar
people and
situations with
avoidance, distress,
restraint
– Takes longer time to
relax in new
situations
– Has more fears and
phobias
– Is timid and cautious
• Uninhibited
– Reacts to unfamiliar
situations with
spontaneity and joy
– Takes shorter time to
relax in new situations
– Has fewer fears and
phobias
– Is not restrained in
new situations
Kagan, Arcus, & Snidman (1993)
• At 4-months,
– Videotaped behavior during familiar and
novel stimuli (voices, mobiles, balloons)
– Rated infants on reactivity (body movement,
crying)
• At 14-months, 21-months, 4.5 years, 8 years
– Videotaped behavior and monitored
physiology
High vs. Low Reactive Infants
(Kagan et al., 1993)
• High reactive
– Show greater fearful
behavior, heart rate
acceleration,
increased blood
pressure
– Smiled and talked
less with unfamiliar
adult
– Were shy with
unfamiliar peer
– Varied within group
• Low reactive
– Showed lesser fearful
behavior, heart rate
acceleration, increased
blood pressure
– Smiled and talked
more with unfamiliar
adult
– Were less shy with
unfamiliar peer
– Varied within group
HEMISPHERE ACTIVATION
Left Hemisphere
Right Hemisphere
• Approach-related
• Withdrawal-related
emotion
• Arousal -> happiness,
resilience in the face of
stress
• Underarousal ->
vulnerable to sadness
and depression
emotion
• Arousal -> fear, disgust,
anxiety
• Underarousal ->
relaxation
HEMISPHERE ACTIVATION
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Davidson’s Evidence from EEG
Reliable from one month to another (r = .66)
More right-sided activation and more intense
negative and less intense positive trait mood
More right-sided activation and more intense
negative affect in response to film clips meant to elicit
fear and disgust
Infants who cried when separated from their mothers
had higher right-sided activation
Inhibited toddlers had low left-sided activation
People with greater left-sided activation had more
natural killer cell activity
Behavioral Genetics
Different ways of estimating genetic influence:
• Experimental animal studies
• Twin studies
• Adoption studies
Heritability
• Twin studies:
• Compare identical twins reared together with
those reared apart
• Assume the similarity between “Together”
twins due to shared genes and environment
• Assume the similarity between “Apart” twins
due only to genes
• THEN:
• “Similarity of together” - “Similarity of Apart” =
environment, and 1- environment = genes
Heritability
• Another form of twin study:
• Compare monozygotic (MZ) together twins
with dyzygotic (DZ) together twins
• Assume similarity of MZ due to genes and
environment
• Assume similarity of DZ due to 1/2 genes and
environment
Heritability
• THEN:
Heritability =
2* (Similarity MZ - Similarity DZ) =
2*((genes + environment) - (1/2 genes +
environment)) =
2* (genes +environment - 1/2 genes - environment)
=
2*(genes - 1/2 genes) = 2*1/2 genes = genes
Heritability
Heritability is an estimate of the percentage of
the variance in a particular characteristic in a
particular study that resulted from genetic
variation in that study.
Variance
0
*
* * * *
* * ** * ** *
3
5
7
Friendliness
10
Variance = ((1-5)2 + (3-5)2 + (3-5)2 + ….. (10-5)2) / N-1
“ Average deviation”
HERITABILITY
Example: Identical twins, different pairs have fairly different backgrounds
30%
Environment
Example: Identical twins, different pairs have
very similar backgrounds
Genes
60%
Environment
Example: Cloned people reared
in very different situations
Genes
0%
Environment
Why is “gene” only circle impossible??
HERITABILITY IS NOT
• The chance that an individual will have a
certain characteristic
• How much influence genes or environment
have on an individual person
• The absolute influence of a gene outside
the particular environment in which the
estimate was made
Heritability is:
an estimate of the percentage of the
variance in a particular characteristic in
a particular study that resulted from
genetic variation in that study.
HERITABILITY
Some results from the major twin studies:
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Intelligence – H = 30% - 70% (some specific cognitive abilities are more
heritable than others)
Activity level, emotional reactivity, sociability-shyness – H = 20% - 50%
Neuroticism, extraversion, impulsivity, monotony avoidance – H = 23%
- 45%
Depression – H = 13% for male relatives and 30% for female relatives
Vocational interests – H =0.43
Religiosity – H =0.49
Traditionalism – H =0.53
Attitudes toward drinking alcohol – H = 51%
Radicalism and toughmindedness – H > 50%
Aggressive, antisocial, criminal behavior – H about 50%
Schizophrenia and Heritability
• Twin studies:
• 0% concordance in identical twins and 6% concordance in
fraternal twins
• Adoption Studies:
Adopted Family
Not S
S
Biological
Family
Not S
1%
3%
S
9%
17%
THE “NATURE-NURTURE” DEBATE
A devil, a born devil, on whose nature
Nurture can never stick; on whom my pains
Humanely taken, all, all lost, quite lost
-The Tempest
NATURE AND NURTURE INTERACTIONS
A Central Theme in Personality and Social
Psychology
The dynamic interaction between the person
and the situation. People come into the
world with some predispositions. They act in
accordance with these predispositions and
get reactions and feedback from the
environment. These reactions and feedback,
in turn, inform, drive, and even determine
their behavior in the future. The cycle
continues.
NATURE AND NURTURE INTERACTIONS
Diathesis-Stress Model
Stress Level
Patient Becomes Ill
Critical Point
Time
Examples
Schizophrenia (genetic diathesis)
Phobias (environmental diathesis)
Alcoholism (possible genetic/environmental)
Depression (possible genetic/environmental)
NATURE AND NURTURE INTERACTIONS
Continuity of Behavior: Two Hypotheses
(Caspi, Bem, & Elder, 1987)
The data on children who tantrum:
Men: downward occupational mobility, erratic
work lives, more likely to divorce
Women: married men with lower
occupational status, more likely to divorce,
ill-tempered mothers
NATURE AND NURTURE INTERACTIONS
Continuity of Behavior: Two Hypotheses
• Cumulative continuity
– We make certain choices, deliberate or not deliberate,
that determine what direction our life goes
• Interactional continuity
– Early temperament forms an interactional style that
evokes reciprocal, maintaining responses from others.
The person acts, the environment reacts, and the
person reacts back.
MAIN POINTS
• Personality comes from a complex dynamic interaction of
nature and nurture
• Nature contributes to personality through genetics, as well as
basic processes such as brain activation, temperment,
neuroanatomy, and biochemistry.
• Nurture contributes to personality through influences such as
parental relationship, sibling competition, environmental
stimulation, and culture.
• Nature and nurture interact from the fetus throughout the life
span. Diathesis, cumulative continuity, and interactional
continuity are some of the mechanisms through which these
interactions occur.