Widespread evidence for non-additive genetic variation in Cloninger's and Eysenck's personality dimensions using a twin plus sibling design

Studies using the classical twin design often conclude that most genetic variation underlying personality is additive in nature. However, studies analyzing only twins are very limited in their ability to detect non-additive genetic variation and are unable to detect sources of variation unique to twins, which can mask non-additive genetic variation. The current study assessed 9672 MZ and DZ twin individuals and 3241 of their siblings to investigate the environmental and genetic architecture underlying eight dimensions of personality: four from Eysenck's Personality Questionnaire and four from Cloninger's Temperament and Character Inventory. Broad-sense heritability estimates from best-fitting models were two to three times greater than the narrow-sense heritability estimates for Harm Avoidance, Novelty Seeking, Reward Dependence, Persistence, Extraversion, and Neuroticism. This genetic non-additivity could be due to dominance, additive-by-additive epistasis, or to additive genetic effects combined with higher-order epistasis. Environmental effects unique to twins were detected for both Lie and Psychoticism but accounted for little overall variation. Our results illustrate the increased sensitivity afforded by extending the classical twin design to include siblings, and may provide clues to the evolutionary origins of genetic variation underlying personality

The clinical and social construction of the Paichais of Macau

The aim of the present study was to understand the clinical and social construction of pathological gamblers in Macau. In Macau, they are called Paichai (扒仔), which literally means “to grab money from others.” This article is a qualitative enquiry into Paichais who gamble in the casinos daily, often for a prolonged period of time. Some Paichais are “resident” gamblers in the casinos who live on the complimentary food and drinks that the casinos provide and sleep on the couches inside the casino premises. To finance their gambling, they hustle and sometimes beg for money. Fifteen participants, ranging in age from 24 to 53 years, were recruited from the casinos in Macau who were repeatedly observed and interviewed. The emphasis of the interviews were to explore the participants’ accounts of how their gambling problem had developed and how gambling influenced their lives and their significant others. The Canadian Problem Gambling Index Problem Gambling Severity Index (PGSI) (Ferris & Wynne, 2001) was used to assess their gambling status. Clinical assessment of the participants was based on the results of clinical interviews, observation notes and the scores on the PGSI. It was found that the majority of the participants could be classified as belonging to the antisocial-impulsive type according to the Blaszczynski and Nower (2002) pathways model of problem and pathological gambling. Paichais can be described as manipulative, cunning, impulsive, reckless and lacking the ability to reflect on their actions. The current study attempts to understand these individuals from the particular social and cultural perspectives of Maca