Suppose you buy the idea popular in psychology that there are stable personality types largely formed in childhood and that the population has relatively stable proportions of these personality types. The Big5 personality types are agreeableness, extraversion, neuroticism, conscientiousness and openness. Often added to this list is Locus of Control. Other traits like analytical ability, empathy, and shyness are also often mentioned in the many lists of personality doing the rounds.
There is some indication that personality is heritable and partially genetic. Genes for shyness have been claimed, as for neuroticism and risk-taking (although there are of course lots of caveats and uncertainties about any claim). The prevalence of those genes differ by region.
If you buy this idea, then the question arises how the distribution of personality types came to be and what sustains it or changes it? What could the forces be that lead to an equilibrium of personality types?
- Perhaps some types are more likely to get killed in certain wars and others are more likely to survive, for instance shy and anxious people. Wars would then lead to increases in the proportions of the personalities that favour survival, whilst in inter-war periods other pressures might prevail that select against shyness.
- Social selection for breeding. Perhaps some types have more children or make more popular breeding partners.
- Social pressures and opportunities that favour proportions of types. One can here think of group types wherein there are ‘slots’ for different personality types in fairly constant proportions. Leaders, followers, creative thinkers, jokers, motivators, etc.
Options 1 and 2 would lead you to believe personality distributions change only slowly outside of catastrophic occasions, and are mainly genetically transmitted. Option 3 fits a more fluid view in which personality is not fixed at birth but more a kind of deep strategy picked up early on but particular to the environment. The possibility that personalities that are at the moment associated with low levels of happiness might be useful in various future eventualities is of course consoling in that some sources of misery might be functional in the long-run. It also raises the possibility that a national personality distribution tells us something about that countries’ history.
Just a thought.