A test of the facultative calibration/reactive heritability model of extraversion.

A model proposed by Lukaszewski and Roney (2011) suggests that each individual's level of extraversion is calibrated to other traits that predict the success of an extraverted behavioural strategy. Under 'facultative calibration', extraversion is not directly heritable, but rather exhibits heritability through its calibration to directly heritable traits ("reactive heritability"). The current study uses biometrical modelling of 1659 identical and non-identical twins and their siblings to assess whether the genetic variation in extraversion is calibrated to variation in facial attractiveness, intelligence, height in men and body mass index (BMI) in women. Extraversion was significantly positively correlated with facial attractiveness in both males (r=.11) and females (r=.18), but correlations between extraversion and the other variables were not consistent with predictions. Further, twin modelling revealed that the genetic variation in facial attractiveness did not account for a substantial proportion of the variation in extraversion in either males (2.4%) or females (0.5%).