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!
Dimensions of personality • Extraversion vs. introversion (E) • Neuroticisms vs. emotional stability (N) • Psychoticism vs. impulse control (P) • Predisposed to each • Collectively 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 Hans Eyesenck
Robert McCrae and Paul Costa • “Big Five” factors of personality • Stability • Extraversion • Openness • Agreeableness • Conscientiousness
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 The Big Five
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 - Conscientious Not 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
First Temperament • Emotionality • Level of excitability for unpleasant feelings Sensitive to unemotional any emotion Arnold Buss and Robert Plomin
Second Temperament • Activity • Physical energy and vigor Constant unmoving movement Arnold Buss and Robert Plomin
Third Temperament • Sociability • Preference for contact/interaction with others Want to be Don’t like to be around others around others Arnold Buss and Robert Plomin
Reflection: Looking at the Big Five and Three Temperaments, which ones do you see having the greatest impact on your life? Assessing Our Traits
Untangling Nature and Nurture Behavior Genetics: the study of the interaction of genes and environment on behavior
“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 Nature vs. Nurture
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.
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
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%.
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, Hank is withdrawn and shy. At 10, Joe is outgoing and friendly. 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? Heritability 100%
Trait Population Heritability Creativity 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% How heritable is that trait? http://www.peele.net/lib/genes.html The Stanton Peele Addiction Website
Twin Studies Identical Twins vs. Fraternal Twins Same 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 Criticism: • Do fraternal twins really have equally similar environments to identical twins? Differences in looks or inborn temperament may cause people to treat you differently. • 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.
Twin Studies Identical 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: • Adoption agencies try to place twins in similar families so the variation in environment may be small, and • There is a very limited sample.
Is child more like adoptive parents… …or biological parents? Adoption Studies 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).
Nature? • Nurture? • Both? • Twins? • Genetic engineering? • Genetic engineering? Examples of theories?
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! Reflection