Nature versus nurture
Personality traits

Identical twins reared apart are far more similar in personality than randomly selected pairs of people. Likewise, identical twins are more similar than fraternal twins. Also, biological siblings are more similar in personality than adoptive siblings. Each observation suggests that personality is heritable to a certain extent. A supporting article had focused on the heritability of personality (which is estimated to be around 50% for subjective well-being) in which a study was conducted using a representative sample of 973 twin pairs to test the heritable differences in subjective well-being which were found to be fully accounted for by the genetic model of the Five-Factor Model's personality domains. However, these same study designs allow for the examination of environment as well as genes.
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