title: The Glass is Half FullandHalf Empty: A population-representative twin study testing if Optimism and Pessimism are distinct systems.
abstract: Optimism and pessimism are associated with important outcomes including health and depression. Yet it is unclear if these apparent polar opposites form a single dimension or reflect two distinct systems. The extent to which personality accounts for differences in optimism/pessimism is also controversial. Here, we addressed these questions in a genetically informative sample of 852 pairs of twins. Distinct genetic influences on optimism and pessimism were found. Significant family-level environment effects also emerged, accounting for much of the negative relationship between optimism and pessimism, as well as a link to neuroticism. A general positive genetics factor exerted significant links among both personality and life-orientation traits. Both optimism bias and pessimism also showed genetic variance distinct from all effects of personality, and from each other.
authors.affiliation: University of Edinburgh, 7 George Square, EH8 9JZ, Edinburgh, UK, +44 131 651 1945.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Bates
keywords: Big Five; Optimism; Pessimism; behavior genetics; personality; twins