Lecture 8: Biological Perspective on Personality Psychology

Definitions: Emotional and behavioral styles present from birth.
New York Longitudinal Study (1977):
- Easy Temperament: Adaptable and less reactive.
- Difficult Temperament: More reactive, may have challenges in adaptability.
- Slow-to-Warm-Up Temperament: Requires time to adjust to new situations.
- affect later-life adjustments
Buss and Plomin’s EASI Model (1984):
- Four temperament dimensions: Emotionality, Activity, Sociability, Impulsivity.
- Identical twin quite high correlation in temperament (genetics play a role)

Kagan's Approach (1994): trace babies up to 4 yo
- When faced with an ugly doll, high inhibition: high avoidance+ reactivity 好大反應
- Low inhibition: low reactivity, does not avoid much 嘗試慢慢approach
- There are inborn differences in temperaments

Parenting Styles and Effortful Control

Effortful Control: Ability to regulate behavior predicts later temptation resistance. Eg. delayed gratification
Parenting styles impact effortful control and moral conscience:

Authoritarian parenting is linked with lower effortful control (because parents get to decide all), and higher sense of moral conscience

Higher effortful control is linked with lower authoritarian parenting, which promotes moral conscience

Goodness-of-Fit Model: environment (eg. parenting) affects more than genes
David’s case: easy temperament in childhood, but parents always spoil him, later develop behavioural disorder
Proves that temperament is not determinalistic, but environments (parenting) plays a more important role

Gene Selection: Adaptive traits facilitate survival and reproduction. Natural selection+ Sociocultural selection

→ eg. Big Five: Why Conscientiousness, Extroversion are seen as good traits? not necessarily good, just we think they are good

Women's conservative strategy:, focusing on finding reliable partners due to heavy investments during pregnancy.
Men’s liberal strategies lean towards maximizing reproductive opportunities and genetic spread due to lower parental investment.

Gender differences in agreeableness found to be smaller in more gender-equal societies.

Cultural Evolutionary Psychology:
- Apart from natural selection, cultural input plays an important role: we develop traits that the society require us to >(more than) genetics
- observational learning → acquire “cognitive gadgets” (abilities, eg. female learn how to cook, male know how to fix things at home)
- cultural carriers: books, word of mouth

Behavioral Genetics: Studies of how genetics and environment influence behaviour
Classic Research Models of adopted twins
- Use of identical twins, raised in two different environments to investigate heritability (how similar they are because of genes)
- Problem of this model: rare subjects, high uncertainties
- strong genetic contributions to intelligence
A more general model of twin pairs (fraternal/identical) raised in the same family

calculate the influence of shared environment and heritability on their based on the correlation(how similar they are) of monozygotic and dizygotic twins raised together
Assume identical twins heritability=1, fraternal twin heritability =0.5
*this assumption is not entirely accurate, cuz this is only population statistics, -> will lead to ecological fallacy if it is applied on individuals (???)
Assume shared environment is the same, but in fact they can have slightly different experiences at home and school
Results: found that shared environment influence is small, unshared environment and genetic influence is much greater.

Reciprocal determinism: People of different genetic dispositions create their environments to reinforce their dispositions
Epigenetics: environment affect gene expression

Findings from Weaver, Meaney, and Szyf (2006):
- Rodent study showing inadequate maternal care → increased fearfulness