Dario Maestripieri

National happiness is related not only to socioeconomic factors but also to biological and ecological factors. This ecological correlational study examined associations between national happiness, cat density, Toxoplasma gondii exposure, and socioeconomic indicators across 93 countries. We hypothesized that countries with higher socioeconomic indicators (e.g., GDP, health expenditure, income level) would exhibit higher happiness levels. In contrast, we predicted that higher T. gondii exposure, both acute (IgM) and chronic (IgG), would be negatively associated with national happiness. Data on happiness measures, cat density, GDP per capita, income classification, health expenditure, and T. gondii seroprevalence in pregnant women (as a proxy for broader population exposure) were obtained from publicly available sources. In line with our hypothesis, we found that national happiness was positively associated with cat density and some socioeconomic factors and negatively associated with IgM seroprevalence. In multivariate analyses, cats per 10,000 inhabitants and IgM seroprevalence remained the strongest independent predictors. Overall, these exploratory analyses suggest that biological and ecological factors are associated with socioeconomic variables in determining national well-being. Future studies of happiness at the national level should integrate both socioeconomic and biological perspectives and include longitudinal and interdisciplinary approaches to elucidate the underlying mechanisms and processes.

Testosterone plays important roles in reproductive behaviour in many species. Despite a common belief that testosterone regulates fluctuations in human sexual desire, there is little direct evidence that relates within-person changes in natural testosterone production to within-person changes in sexual desire. Here, we measured daily salivary testosterone concentrations from 41 adult men for one month, along with daily self-reports of sexual desire ( n = 759 observations for the main analyses). We analysed concurrent relationships between within-person changes in testosterone and desire, and also lagged relationships that were analysed using a continuous-time modelling framework. We found no evidence for significant, positive relationships between testosterone and desire, which argues against the notion that day-to-day changes in eugonadal men’s baseline testosterone regulates changes in their sexual desire. However, additional analyses provided preliminary evidence for a positive relationship between testosterone and self-reported courtship effort, particularly on days when single participants interacted with potential romantic partners. Our findings add original evidence regarding day-to-day associations between testosterone and desire, and suggest that testosterone above minimum threshold concentrations does not increase sexual desire. We propose that the evolved functions of testosterone in human males are more closely associated with courtship efforts than with sexual desire.

In romantic couples, there is usually an asymmetry in decisional power such that one partner is dominant and the other is subordinate. This study investigated the role of sex, ethnicity, self-assessed social status, personality traits, and power motivation (both explicit and implicit) as potential determinants or correlates of couple dominance in a mixed-sex sample of 50 college students. Through a previously validated questionnaire, participants indicated whether they were dominant or subordinate in their romantic relationship, or whether the latter was egalitarian. Major personality domains, narcissism, psychopathy, borderline, autistic-like traits, and explicit power were assessed through questionnaires. Participants also underwent a Picture Story Exercise to evaluate their implicit motives. Being dominant and having high explicit, but not implicit, power motivation were associated with some psychopathic, narcissistic, and/or borderline traits, while autistic-like traits were associated with being subordinate. Traits such as extraversion, conscientiousness, and honesty-humility had weak associations with couple dominance and/or explicit or implicit power motivation. Our findings have implications for the understanding of dominance dynamics within couples and the relationship between personality traits and power motivation.

The “challenge hypothesis” predicts higher male–male aggressive behavior along with increases in testosterone levels during times of reproductive challenges and social instability. In addition, in some primate species, higher glucocorticoid levels can be observed as well, but this is usually modulated by dominance rank. We studied rank-related aggressive behavior, mating activity, and fecal testosterone and glucocorticoid metabolites (fTm and fGCm) in male stumptail macaques (Macaca arctoides) in order to test some predictions of the “challenge hypothesis”. Over a 20-month period, we collected data on aggressive behavior and copulation, as well as fecal samples (n = 700) to quantify fTm and fGCm in seven adult stumptail males living in captivity. During periods of mating activity, male-to-male aggression increased in higher- and middle-ranking males. Neither fTm nor fGCm levels predicted male-to-male aggression. fGCm levels (but not fTm) were positively associated with male-to-female aggression; however, this association was pronounced during periods of mating activity. fGCm levels differed according to social rank, with middle-ranking males having the highest levels. Both hormones were higher during periods of mating activity, but only in higher- and middle-ranking males. Taken together, our findings partially support the challenge hypothesis in a non-seasonal primate and shed some light on the unique social and mating system of the stumptail macaque.