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BIOLOGICAL PSYCHOLOGY
NATURE VS. NURTURE
Gordon Allport
Founder of the Trait Theory◦Predispositions to respond, in a same or similar manner, to different stimuli
◦After meeting Freud, Allport felt there was too much emphasis on inner drives
Trait Theories of Personality
Personalities described by main characteristics (traits)
Traits (honesty, laziness, ambition, outgoing) thought to be stable throughout life
Key Ideas of Trait Theory
We are psychophysical beings Mind and body function together
Personality develops from both mental and biological influence
Each person is unique Everything is a characteristic of us and no one else
Heredity (genetics) provides “raw materials” Environment shapes, expands, or limits heredity
(raw materials)
Key Ideas of Trait Theory
In other words: individual combination of genes (except for identical twins) + the environment = personality
Two personalities Childhood (more biological) Adulthood (more environmental) Childhood personality does not determine adult
personality!
Other Trait Theorists
Hans Eyesenck
Dimensions of personality
1. Extraversion vs. introversion (E)
2. Neuroticisms vs. emotional stability (N)
3. Psychoticism vs. impulse control (P)
Predisposed to eachCollectively makes up
personality
Hans Eyesenck
Extraversion vs. introversion (E)
Extraverts◦Lower level of cortical
(brain) arousal◦Seeks stimulation
Introverts◦Higher level of cortical
arousal◦Shies away from stimuli
Hans Eyesenck
Neurotic vs. emotional stability (N)
Neurotic ◦Greater brain activity in
sympathetic branch of autonomic nervous system
◦Alarm system – “fight, flight, or freeze”
◦Overreacts to even mild stress
Emotional stability◦More subdued responses◦More “level headed”
Hans Eyesenck
Psychoticism vs. Impulse control (P)
Psychoticism◦ Aggressive◦ Anti-social◦ Tough minded◦ Cold◦ Ego-centric◦ Cruel, hostile, insensitive◦ Men tend to score higher
(hormonal)Impulse control
◦ Can channel aggression into appropriate activity
Hans Eyesenck
Heredity plays greater role than environment
Descriptors of E◦Sociable, lively, active,
assertive, sensation seeking, carefree, dominant, venturesome
Descriptors of N◦Anxious, depressed,
guilt feelings, low self-esteem, tense, irrational, shy, moody
Descriptors of P◦Aggressive, cold,
egocentric, impersonal, impulsive, anti-social, creative, tough-minded
Robert McCrae and Paul Costa
“Big Five” factors of personality
StabilityExtraversionOpennessAgreeablenessConscientiousness
The Big Five
Stability (calm or anxious, secure or insecure, self-satisfied or self-pitying)
Extraversion (sociable or retiring, fun-loving or sober, affectionate or reserved)
Openness (imaginative or practical, variety or routine, independent or conforming)
Agreeableness (soft-hearted or ruthless, trusting or suspicious, helpful or uncooperative)
Conscientiousness (organized or disorganized, careful or careless, disciplined or impulsive)
The Big Five
According to Big Five trait theory:
Traits are stable over time
Can be attributed to genetics
Describes personality equally across different cultures
Predicts other attributes
Correlations with the Big Five:Which behaviors correlate?
Protested injustice- Emotionally stable, open
Fell in love at first sight- Extraverted
Have not been in therapy- Emotionally stable
Been in therapy- Open
Thrown a large party- Extraverted
Kept a diary- Open
Listen to music by self in dark- Open
Correlations with the Big Five:Which behaviors correlate?
Read fewer than 12 books per year- Extraverted
Never cheated on a test- Conscientious
Never pulled all-nighter to finish assignment
- ConscientiousNot likely to become addicted to
Internet-Extraverted
Dated a person of a different race- Open
Written a poem spontaneously- Open
Arnold Buss and Robert Plomin
Temperament◦Building blocks of
personality◦Everyone has levels
of all three◦Primarily biological;
can be adapted by environment
Arnold Buss and Robert Plomin
First TemperamentEmotionality
◦Level of excitability for unpleasant feelings
Sensitive to unemotionalany emotion
Arnold Buss and Robert Plomin
Second TemperamentActivity
◦Physical energy and vigor
Constant unmoving
movement
Arnold Buss and Robert Plomin
Third TemperamentSociability
◦Preference for contact/interaction with others
Want to be Don’t like to be
around others around others
Assessing Our Traits
Reflection: Looking at the Big Five and Three Temperaments, which ones do you see having the greatest impact on your life?
Untangling Nature and Nurture
Behavior Genetics: the study of the interaction of genes and environment on behavior
Nature vs. Nurture
“Nature” = role genes have on a trait
“Nurture” = role life experience has on trait
Eysneck, McCrae and Costa, and Buss and Plomin all used twin studies in research
Biological Theories of Personality
What % of the variation in a population is attributable to genes? - heritability
Not sure; BUT temperaments do seem to be stable from infants to old age.
Heritability
Percentage of trait variation in a group that can be attributed to genetic differences (can be inherited)
In other words, what role do genetics play?◦0% means genes play no role◦100% means genes play entire role
Depends on the population
Heritability
Sara is very outgoing and agreeable
Suzy is timid and non-conforming
If this pair of IDENTICAL twins is my population, what percent of the personality differences is attributable to genetic differences between them?
The heritability is 0%.
Heritability
Joe and Hank are not related. At birth, both were placed in identical environments that were maintained identical until they were 10 years old.
At 10, Joe is outgoing and friendly.
At 10, Hank is withdrawn and shy.
In this (very small) population, what is the heritability of their personality traits? In other words, what percentage of the difference is attributable to genes?
100%
How heritable is that trait?
Trait Population HeritabilityCreativity adolescents 25%Extraversion adults 30-50%Autism general 90-95%Depression general 40-55%Sleep quality general 35%TV viewing 3-5 year olds 10-45%Religious beliefs general 0%Religious conservatism women 40%Divorce general 55%Height women 92%
http://www.peele.net/lib/genes.html The Stanton Peele Addiction Website
Identical Twins vs. Fraternal TwinsSame genes, Different genes,Same environment Same environment
Therefore, greater differences between the two groups indicate greater heritability (“Nature”). The trait might appear to have a large genetic component.
Twin Studies
Twin Studies
Criticism: 1) Do fraternal twins really have equally similar environments to identical twins? Differences in looks or inborn temperament may cause people to treat you differently.
2) Identical twins may share a placenta but fraternal twins do not. Thus, we can’t eliminate prenatal environments as the cause of the differences between the two groups.
Increased risk of schizophrenia if twin develops disease
0%
10%
20%
30%
40%
50%
60%
Fraternal twins Identical twins
% in
cre
ase
Twin StudiesIdentical Twins Reared Together v. Identical Twins Reared Apart
Same genes, Same genes,Same environment Different environment
Greater difference between these two groups indicates greater role of the environment (“nurture”).
Twin Studies
Criticisms: 1) Adoption
agencies try to place twins in similar families so the variation in environment may be small, and
2) There is a very limited sample.
Similarity of IQ Test Scores in Twins
0.5
0.6
0.7
0.8
0.9
Identical twins rearedtogether
Identical twins rearedapart
Co
rrela
tio
n
Adoption Studies
Is child more like adoptive parents…
…or biological parents?
Adoptive Parents - Nurture Biological Parents - Nature
Adoption Studies
Note: Two related siblings that grow up in the same family are strikingly different in personality (as I’m sure many of you can attest to).
Similarity of Values Between Adopted Children and their Parents
0
0.1
0.2
0.3
0.4
0.5
Biological parents Adoptive parents
Co
rrela
tio
n C
oeff
icie
nt
Similarity of Temperament Between Adopted Children and their Parents
0
0.1
0.2
0.3
0.4
0.5
0.6
Biological parents Adoptive parents
Cor
rela
tion
Coe
ffici
ent
Examples of theories?
Nature?Nurture?Both?Twins?Genetic engineering?Genetic engineering?
Reflection
What is your opinion of the nature vs. nurture theory of psychology? In other words, do you believe nature is dominant, nurture is dominant, or it’s a combination of both?
Please explain your answer!