بررسی ژنتیکی رفتاری از سبک های طنز و همبستگی آنها با ابعاد پنج عامل بزرگ شخصیتی

Four hundred and fifty six pairs of adult twins completed the Humor Styles Questionnaire – which measures two positive and two negative styles of humor – and the NEO-PI-R, which measures the Big-5 personality traits. Univariate behavioral genetic model-fitting revealed that individual differences in the two positive humor styles (affiliative and self-enhancing) and all five of the Big-5 traits were largely attributable to genetic and nonshared environmental factors, whereas individual differences in the two negative humor styles (self-defeating and aggressive) were largely attributable to shared and nonshared environmental factors. Several significant phenotypic correlations were found between each of the four humor styles and the Big-5, and multivariate behavior genetic analyses revealed that these observed correlations were themselves entirely attributable to genetic and nonshared environmental factors.

To what extent are individual differences in sense of humor caused by genetic or environmental factors? Previous behavioral genetic (BG) investigations addressing this question have been quite limited and have yielded different results depending on how the sense of humor construct is conceptualized and measured. One approach taken by past researchers is to conceptualize sense of humor in terms of humor appreciation, which is typically assessed by having participants rate the perceived funniness of a series of jokes or cartoons. Correlational research has shown that appreciation ratings of various types of humor stimuli are associated with such traits as tolerance for ambiguity, sensation-seeking, and conservatism (Ruch, 1992), but are generally unrelated to individuals’ tendencies to produce or engage in humor and laughter in their daily lives (Köhler & Ruch, 1996). By comparing the relative similarity of monozygotic (MZ) and dizygotic (DZ) twins, BG studies attribute individual differences in traits as being due to genetic differences between people and/or to one of two types of environmental influences: referred to as shared or nonshared. Shared environmental factors are those aspects of the environment that twins have in common – factors such as being raised by the same parents in the same home – these factors contribute to similarity between twins. Nonshared environmental factors refer to things that one twin experiences and that his or her co-twin does not experience – twins, for example, might develop friendships with different groups of people – these factors contribute to differences between twins. In an early BG study, Nias and Wilson (1977) found moderate correlations between 100 pairs of MZ and DZ twins on funniness ratings of four categories of cartoons, but the MZ and DZ correlations did not differ in magnitude, suggesting a lack of genetic influence. Subsequent model-fitting analyses of the same data (Wilson, Rust, & Kasriel, 1977) indicated that individual differences in funniness ratings of nonsense, satirical, and sexual cartoons were entirely attributable to shared and nonshared environmental factors (referred to as a CE model), whereas differences in the appreciation of aggressive cartoons were attributable to additive genetic and nonshared environmental factors (an AE model). More recently, Cherkas and colleagues (2000) similarly found evidence of a CE model in a study of 127 pairs of female MZ and DZ twins who rated the funniness of five Gary Larson Far Side cartoons. In summary, the limited research conducted to date suggests that, when sense of humor is defined in terms of the appreciation of particular types of jokes and cartoons, individual differences are primarily due to differences in the shared and nonshared environment and not to genetics. Thus, people’s tendency to enjoy these types of humorous stimuli seems to develop largely as a consequence of learning experiences both within and outside the family environment, rather than being innate. As an alternative to the humor appreciation approach, most recent research on individual differences in sense of humor has made use of self-report scales to assess the degree to which individuals laugh and smile frequently, notice and enjoy humor, use humor to cope with stress, and maintain a cheerful and playful outlook (e.g., Martin, 1996). These types of measures tend to be associated with extraversion, and have been found to predict individuals’ humor creation abilities, peer ratings of sense of humor, and tendency to produce humor in daily life (for reviews, see Martin, 2007 and Ruch, 1998). Importantly, these self-report humor tests tend to be uncorrelated with measures of humor appreciation (Köhler & Ruch, 1996), indicating that these two measurement approaches assess quite different aspects of sense of humor. Although the existing research is again very limited, previous BG investigations using self-report measures of humor generally suggest that variance in these traits is primarily due to both genetics and the nonshared environment (an AE model). In an early study involving more than 1000 MZ and DZ adolescent twin pairs, Loehlin and Nichols (1976) included a single item asking participants to rate the degree to which they felt they had a “good sense of humor”. A significantly larger correlation was found between the MZ as compared to the DZ twin pairs, suggesting a genetic contribution to individual differences in self-rated sense of humor. Similarly, in a study of 98 pairs of adolescent siblings who were either nonadopted (sharing 50% of their genes) or adopted at birth (sharing none of their genes), Manke (1998) found evidence that individual differences in the self-reported tendency to engage in humorous interactions with family members (mother and siblings) were due to genetic and nonshared environmental influences (an AE model), whereas differences in humorous interactions with friends were due to the shared and nonshared environment and not to genetics (a CE model), perhaps because these latter relationships are of shorter duration and have therefore had less time to stabilize. In contrast to most other self-report humor scales, which focus on socially desirable aspects of humor, Martin and colleagues (2003) have developed a measure that distinguishes between potentially beneficial and potentially detrimental uses of humor. The Humor Styles Questionnaire (HSQ) assesses four styles of humor, two of which are hypothesized to be potentially beneficial to psychosocial well-being (affiliative and self-enhancing) and two potentially detrimental (self-defeating and aggressive). Affiliative humor refers to the tendency to tell jokes, humorous anecdotes, and witticisms as a means of amusing others and facilitating relationships. Self-enhancing humor refers to the tendency to maintain a humorous outlook on life even during times of stress, and to use humor as a coping strategy. In contrast, aggressive humor refers to the use of sarcasm, teasing, and ridicule, as a means of enhancing the self at the expense of one’s relationships with others. Finally, self-defeating humor involves excessively self-disparaging humor, attempts to amuse others by doing or saying funny things at one’s own expense, and laughing along with others when being ridiculed or disparaged. Studies using the HSQ have found that the two positive humor styles tend to be significantly correlated with previous self-report humor measures, whereas the two negative styles are generally unrelated to these measures, indicating that they assess different components of humor (Martin, Puhlik-Doris, Larsen, Gray, & Weir, 2003). Like other self-report humor tests, the HSQ scales are also generally uncorrelated with scores on measures of humor appreciation. Validational support for the HSQ includes differential and theoretically-relevant patterns of correlations between the four scales and a range of measures, including peer ratings of humor styles, positive and negative moods, psychological well-being, self-esteem, optimism, hostility, competitiveness, loneliness, shyness, intimacy, social competence, and emotional intelligence (for reviews, see Martin, 2007 and Martin et al., 2003). One major goal of the present study was to investigate genetic and environmental contributions to individual differences in the four styles of humor assessed by the HSQ using a large sample of MZ and DZ twins. In view of previous BG research showing evidence of genetic and nonshared environmental contributions to individual differences in self-report humor measures, and given that the affiliative and self-enhancing humor scales tend to be correlated with other self-report humor measures, we predicted that an AE model would be found for these two positive humor styles as well. However, we were unsure about what pattern of results to expect for the two negative humor styles (aggressive and self-defeating), because these are less consistently related to other self-report humor measures. On the one hand, since they are correlated with a number of other personality traits that have previously been shown to have a sizable genetic contribution, these humor styles might also be expected to have a genetic contribution. On the other hand, they might be more similar to humor appreciation measures (although they are conceptually and empirically distinct) and show only environmental contributions. An additional goal of this study was to examine associations between the four humor styles and the Big-5 personality dimensions. In a previous study involving 152 adult participants, Martin and colleagues (2003) examined correlations between the HSQ and the Big-5 as measured by the Revised NEO Personality Inventory (NEO-PI-R; Costa & McCrae, 1992). The results revealed a different pattern of correlations for each of the four humor styles. Affiliative and self-enhancing humor were both positively correlated with extraversion and openness, with self-enhancing humor also correlating negatively with neuroticism and positively with agreeableness. In contrast, aggressive and self-defeating humor correlated positively with neuroticism and negatively with agreeableness and conscientiousness. Thus, the different styles of humor seem to represent different ways in which humor is used or expressed by individuals having different patterns of general personality traits. In the present study, we sought to determine whether this pattern of phenotypic correlations would be replicated in a larger sample of participants. In addition, by using data from MZ and DZ twins, we were able to compute genetic, shared and nonshared environmental correlations between the four humor styles and the Big-5 dimensions. In this way, we could determine the degree to which any observed associations between the humor styles and these broader personality dimensions may be due to common genetic and/or environmental factors. Given that previous research has generally supported an AE model for the Big-5 dimensions, we expected that observed correlations with humor styles would be due to both common genes and the nonshared environment.