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, 10 (6), 533-542

The Glass Is Half Full and Half Empty: A Population-Representative Twin Study Testing if Optimism and Pessimism Are Distinct Systems

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The Glass Is Half Full and Half Empty: A Population-Representative Twin Study Testing if Optimism and Pessimism Are Distinct Systems

Timothy C Bates. J Posit Psychol.

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.

Keywords: Big Five; Optimism; Pessimism; behavior genetics; personality; twins.

Figures

Figure 1
Figure 1
Cholesky (A) and Independent Pathway (B) models. Note: In the Cholesky model, each latent variable can load on all variables to beneath or to its right. This allows a saturated baseline model against which hypotheses can be tested. In the Independent Pathways model, general factors (1 in this case) loading on all variables are posited for each of A, C, and E. In addition, each measured variable is allowed to have unique variance components. For clarity only the genetic paths are shown, but this model is duplicated for each of shared environment (C) and unique environment (E). The model is also duplicated for each twin, and in two groups: one for MZ and one for DZ twins.
Figure 2
Figure 2. Independent Pathway model of personality, optimism, and pessimism
Note: Path estimates followed by 95% CIs in square brackets (decimal places omitted for clarity). “A genetic” is a general genetic factor. “as” latent variables are traits-specific additive genetic effects. “C family env” represents a latent shared-environment effect on Neuroticism, optimism, and pessimism.

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