personality nature and nurture

Twin and family studies

40% for mz. Lower in family/adoption studies where the resemblance between parent/biological child.

Does not seem to vary by sex

Candidate gene approach

Late 1990s/early 2000s. Hypothesis driven. Constrained by prior knowledge. Allows systematic scanning

CGA and E

Dopamine. People with at least one 7-repeat allele have higher E

CGA and N

Serotonin. Short allele associated with decreased serotonergic function. 3-4% of total variation

Problem of non-replication

Effects are small, only few % explained, which may vary with sex/ethnicity. So need thousands of ppts

Genome wide association studies

Instead of candidate gene, set markers across whole genome. Should find all variants associated with phenotype of interest.

Hypothesis free, exploratory, lower power. Large number of variants

GWAS problem of missing heritability

Explains <1% of variance in personality, usually not replicated across studies

Epigenome

Secondary layer of biochemical info that modify or mark genome so alters instructions given by DNA.

Influence which genes are turned on and off

Can be altered by environment, and can be passed down

Belsky et al hypothesis

Individuals differ in sex and relationship behaviours. Unsupportive care from caregivers in first 5-7 years of life.

This is predicted to stimulate early pubertal maturation, short term and unstable pair bonds, limited parental investment

Nettle childhood experience and age of first pregnancy

3000 women, measures of stability in first 7 years. Breastfed, longest separation from mam, dads role, residential moves

Puzzle of causality

Candidate genes are complete genes, SNPs are part of genes, markers, modifiers. But basic mechanism of organismal biology requires genes

RBFOX1: linked to Alzheimer’s, autism, bipolar, Tourette’s

Eco Devo biology

Have about 20,000 genes that code for proteins, but between 100,000 and 1,000,000 unique types of protein

Development systems theory

All biological processes operate by continually assembling new structures. Each structure transcends the structures that it made.

We are each developmental systems, genetic effects are impossible to interpret outside the developmental system. So genetics are inseparable from environment

SNPs clusters

G*G interactions. Found 42 SNP that identified 727 gene loci and were significantly associated with one or more character profiles

These appeared consistent across cultures and environments. 50-58%

Big 5 mechanisms - extraversion

Responsiveness of midbrain reward systems

Big 5 mechanisms - neuroticism

Responses of negative affect/distress systems

Big 5 mechanisms - openness

Reduced latent inhibition

Big 5 mechanisms - conscientiousness

Functioning of goal priority network

Big 5 mechanisms - agreeableness

ToM, empathy