PSYC10004 Lecture Notes - Lecture 21: Twin Study, Behavioural Genetics, Reductionism
Biological Approaches to Personality
Skim this: more detail here than you need to know
1. To say biological differences underlie personality is not to imply that social and cultural
differences are unimportant
2. Possible to investigate biological bases of personality without claiming they determine
persoalit ariatio deteriis or that persoalit a e redued to the
redutiois
3. Division between biological and sociocultural influences and explanations is to some extent
a false one. Social influences affect our biology as biological influences affect our social
behaviour
Three main vantage points biology provides:
1. We can ask whether personality traits are subject to genetic influences; partially inherited
2. Whether personality characteristics are reflected in distinct patterns of brain activity
3. Can ask how individual differences in personality might make sense in light of evolution
The Genetics of Personality
• 99.9% of base pairs identical for all people
• Remaining 3 million base pairs take two or more alternative forms as a result of genetic
utatios ad ko as polorphiss
• Behavioural genetics attempts to understand the influence that these inherited genetic
differences have on psychological characteristics such as cognitive abilities, mental disorders
and personality traits
• Behavioural geneticists have three main methods for studying: family studies, twin studies,
adoption studies
Behavioural Genetic Research Methods
Family Studies: assess resemblance of family members on characteristic of interest
Twin Studies: alternative means of testing and estimating genetic contributions to a characteristics
Monozygotic/Identical Twins are genetically identical, Dizygotic/Non-identical twins are
genetically no more similar than typical siblings
Adoption Studies: examines and compares resemblance of adopted children to biological and
adoptive parents
Limitations:
• Family studies – fail to disentangle genetic and environmental influence; closer relatives are
more similar genetically and environmentally
• Twin studies – vulnerable to violations of equal environments assumption and that twins are
unrepresentative of general population
• Adoption studies – vulnerable to same representativeness problem as twin studies, and
biological and adoptive parents might systematically resemble another, biological also
parents contribute genes and pre-natal environment
Genetic Influences and Heritability
Heritability: proportion of observed variation in characteristic of interest that can be accounted for
by variation in the two kinds of influences
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Document Summary
Social influences affect our biology as biological influences affect our social behaviour. Family studies: assess resemblance of family members on characteristic of interest. Twin studies: alternative means of testing and estimating genetic contributions to a characteristics. Monozygotic/identical twins are genetically identical, dizygotic/non-identical twins are genetically no more similar than typical siblings. Adoption studies: examines and compares resemblance of adopted children to biological and adoptive parents. Eg. susceptibility to accidents and divorce are partially heritable, pro(cid:271)a(cid:271)l(cid:455) as the(cid:455)(cid:859)re asso(cid:272)iated (cid:449)ith herita(cid:271)le personality traits: similarly, we actively expose ourselves to environments that match genetic dispositions, genes influence how we experience life events. Specific personality-related genes: research shows genetic differences are major source of personality variation, research incomplete: indicates some genes influence personality, not which ones and how, next step is to locate specific genes that contribute to personality variation. Emotional states: hypothesised neuroticism is underpinned by variation in reactivity of visceral brain, highly reactive = prone to emotional instability.
