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The Biological Tradition

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1 The Biological Tradition
Examples from lecture on history: The 4 humors (Melancholic, Sanguine) Phrenology Body Types • what other examples do they recall?

2 The Biological Tradition
Phineas Gage ( )

3 Temperament Individual differences in general mood or quality of emotional response that are moderately stable, inherited, and biologically based

4 Inhibited versus Uninhibited Children (Kagan, 1994)
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

5 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

6 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 • high reactive defined as high movement + high crying at time 1 • according to Kagan, about 15% of extremely reactive babies remain fearful and the rest become normal. None become fearless or extraverted • study of 31 fetuses -- monitored on multiple occasions -- high fetal activity levels associated with increased difficulties, unadaptability, and unpredictability after birth

Left Hemisphere Approach-related emotion Arousal -> happiness, resilience in the face of stress Underarousal -> vulnerable to sadness and depression Right Hemisphere Withdrawal-related emotion Arousal -> fear, disgust, anxiety Underarousal -> relaxation

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

9 Different ways of estimating genetic influence:
Behavioral Genetics Different ways of estimating genetic influence: Experimental animal studies Twin studies Adoption studies • show the giggle twins • animal studies -- how characteristics hold up over generations (e.g.: breeding fruit flies) -- what traits can you breed in? • twin and adoption studies attempt to compare the variations between people with varying degrees of genetic relatedness • both are attempts to “account for observed variance” by partitioning into genetic and environmental contributions

10 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 • What’s wrong with this over-simplified logic? • adoptive studies use similar logic -- are adopted children more like their biological or their adoptive parents? If similar to biological we assume big genetic contribution, if similar to adoptive we assume big environmental

11 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

12 Heritability Heritability = 2* (Similarity MZ - Similarity DZ) =
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

13 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.

14 Variance * * * * * * * * • when we explain variance we are explaining why everyone in our sample did NOT get the same score 7 3 5 10 Friendliness Variance = ((1-5)2 + (3-5)2 + (3-5)2 + ….. (10-5)2) / N-1 “ Average deviation”

15 HERITABILITY 30% 60% 0% Why is “gene” only circle impossible??
Example: Identical twins, different pairs have fairly different backgrounds 30% Environment Genes Example: Identical twins, different pairs have very similar backgrounds 60% Genes Environment Example: Cloned people reared in very different situations • explain that the circles in diagram represent variance between people as a group - NOT between individuals - and that it is variance in a particular variable (eg: trait) • note that heritability estimates depend on how much variance in genes or environment that there is to be explained in that population - dividing up variance, therefore all the components must add up to one. Sometimes only genes and environment considered, sometimes their interactions as well • note that it doesn’t matter whether it’s twins or not, since the variance will be across the entire sample (twins become like a single data point and it is there difference from other twins that matters) • Note that typical twin studies are like the second situation, therefore heretibility estimates large. If they were more like first circle, ie reared in very different social situations, then heretibility estimates would be smaller. * Why is a gene only circle impossible? - No such thing as identical environments across the lifespan. 0% Environment Why is “gene” only circle impossible??

16 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

17 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.

18 HERITABILITY Some results from the major twin studies:
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%

19 Schizophrenia and Heritability
Twin studies: 0% concordance in identical twins and 6% concordance in fraternal twins Adoption Studies: 1% 3% 9% 17% Not S S Adopted Family Biological Family • cell entries are percentage of children who develop schizophrenia • population average is 1% • Note that this is a perfect example of the idea of “interaction effects”

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 • The debate is not new…. • What does the quote mean?

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. • remind them of our personality versus situation discussion earlier • this can be mapped onto the nature (personality) versus nurture (situation) debate

Diathesis-Stress Model Examples Schizophrenia (genetic diathesis) Phobias (environmental diathesis) Alcoholism (possible genetic/environmental) Depression (possible genetic/environmental) Stress Level Time Critical Point Patient Becomes Ill

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

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.

25 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. • follow this with case-study exercise in building interactional models

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