Doctoral defence: Kadri Arumäe “Personality traits and body weight: from accurate descriptions to tests of causation”

On 30 August at 14:15 Kadri Arumäe will defend her doctoral thesis “Personality traits and body weight: from accurate descriptions to tests of causation” for obtaining the degree of Doctor of Philosophy (in Psychology).

Supervisors:
Uku Vainik, University of Tartu, McGill University (Canada)
Rene Mõttus, University of Tartu, University of Edinburg (UK)

Opponent:
Yannick Stephan, University of Montpellier (France)

Summary
Motivated by the objective to identify modifiable causes of excess weight, several decades of research has explored psychological correlates of body weight. For instance, body weight is commonly believed to be influenced by personality traits: if some trait-related behaviours affect energy intake or expenditure, their effects on weight should accumulate as they are repeated. However, tests of causality between them have been scarce and inconclusive. One of the two objectives of the dissertation was to test causality in personality trait–body weight associations. Across two studies, molecular genetic, twin, and longitudinal data were employed. Contrary to widespread beliefs, no robust effects from personality traits to body weight were found, although this does not preclude deliberate trait change affecting body weight—a question left for future studies. Instead, both studies indicated that causality may predominantly flow from body weight to personality traits. While the two genetic analyses suggested that body weight may influence numerous narrow traits, longitudinal analyses identified influences on agreeableness, conscientiousness, and several finer-grained traits. Several mechanisms could plausibly account for these links, including social feedback, physical limitations, and physiological processes like inflammation. The other objective of the dissertation was to provide more accurate descriptions of trait–body weight correlations, which could also provide input for novel (causal) hypothesis and further empirical investigations. The two studies devoted to this objective replicated several well-known associations (with traits like activity, organization, and anger), but also identified novel associations (with traits including altruism, obedience, conventionality, and preference for the familiar), besides indicating that the oft-reported link between BMI and assertiveness is more likely driven by lean mass than fat mass.