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Browsing by Subject "twins"

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  • Cloningerin psykobiologisen teorian temperamenttipiirteiden yhteys alkoholinkäyttöön nuorilla aikuisilla 
    Tapola, Lauri (2008)
    The temperamental traits of Cloninger's personality theory (novelty seeking, harm avoidance, reward dependence and persistence) reflect independent systems of central nervous system deciding responses toward new, rewarding and aversive stimuli. Thus, certain temperamental traits and their combinations may predispose to heavy drinking and alcohol dependence. Hence, the aim of the present study was to investigate associations between temperamental traits and the amount of alcohol consumption, frequency of heavy drinking and the maximum number of drinks per occasion. In this study, we investigated also whether these associations are only confounded by between-family differences in genetic and environmental factors. Furthermore the associations between temperamental trait combinations that reflect Cloninger's typology of alcoholism and alcohol use were studied. The subjects (n=401) in the current study were a group of FinnTwin16 study participators, Finnish twins born in 1974-79. Temperament was measured with TCI-R (Temperament and Character Inventory-Revised) a self-report form. The amount of alcohol consumption was asked by Semi-structured interview (Semi-Structured Assessment of Genetics of Alcoholism = SSAGA). The frequency of heavy drinking and maximum number of drinks per occasion were asked by mail form. In accordance with previous studies, novelty seeking had a positive relationship with the amount of alcohol consumption, frequency of heavy drinking and the maximum number of drinks per occasion in both genders. In this study, the association was proven independent of between-family differences in genetic and environmental factors that are associated to both novelty seeking and alcohol use. Surprisingly, reward dependence was negatively related to the maximum number of drinks per occasion in both genders. Persistence had a weak positive relationship with maximum number of drinks per occasion in men. The temperamental trait combinations that reflect Cloninger's typology of alcoholism did not differ from the other combinations in regard to alcohol use as hypothesized. The results confirm the previous finding about the relationship between novelty seeking and alcohol use. Support for Cloninger's typology of alcoholism in regard to combinations of temperamental trait was not achieved in this study.
  • Sex differences in cognitive functions : a study of same-sex and opposite-sex twin pairs 
    Vuoksimaa, Eero (2004)
    Studies concerning cognitive sex differences have indicated that, on average, females outperform males in some verbal abilities, whereas males outperform females in some visual-spatial abilities. Prenatal hormones play important role in sexual differentiation. Presence of androgens is believed to cause male brain differentiation. According to animal studies prenatal exposure to testosterone in females can result in masculinized behaviour or physiological traits. Human studies of possible masculinization of females from opposite-sex twin pairs are controversial. Some studies have indicated that female members of opposite-sex twins may be masculinized in some traits, while other studies show no evidence of masculinization. Hence the aim of the present study is to investigate sex differences and possible masculinization of cognitive functions in young adult twins. Subjects (N=336) were recruited from the ongoing longitudinal FinnTwin16 study of Finnish twins born in 1974-1979. Results indicate female superiority in verbal and executive functions and male superiority in visual and working memory functions. Further, in female members of opposite-sex twin pairs the visual abilities were enhanced to the male level. However, they still outperformed males in verbal and executive functions. In male members of opposite-sex twin pairs there were no signs of better performance in functions that favored females. Nor there were evidence of reduced performance in functions that favored males. This study suggests that there occurs masculinization of cognitive functions in females who have a male co-twin. In contrast, males with female co-twins are not feminized in their cognitive functions. These results indicate some benefits of twinship in female members of opposite-sex twin pairs in cognitive abilities. Whether the masculinization is a result of organizational effects of prenatal testosterone or postnatal environmental influences could not be resolved. Future research, with control over environmental influences, is needed to determine the origin of masculinization of cognitive abilities.

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