Adaptive Human Behavior and Physiology最新文献

Objectives

Human females may attract men and solicit their approach through different nonverbal displays and signals. In many non-human animals, a lordosis posture in a female is a reliable signal of sexual receptivity. Recently, it has been argued that this posture is linked to a similar signal between men and women. The current research across three investigations aimed to test the predictions arising from the sexual receptivity hypothesis of lordosis posture.

Methods

Using realistic 3D generated stimuli, both men and women viewed women’s arched back postures in standing, supine and quadruped poses (Studies 1 and 2) and were asked to rate them for perceived sexual receptivity. In Study 3, a male model was used.

Results

In Study 1 we tested whether the arched back posture in women is an indicator of sexual receptivity. Results showed that both men and women associated increases in the arch of the back with higher sexual receptivity in women. Study 2 predicted and confirmed that sexual receptivity is also perceived from non-standing postures, namely supine and quadruped poses. Study 3 tested the prediction that the perception of sexual receptivity is specific to the posture being adopted by women.

Conclusion

Collectively this research provides support for the sexual receptivity hypothesis of lordosis posture by showing that sexual receptivity is perceived by an increase in the arch of the back (Study 1), it is perceived as sexually receptive irrespective of the body posture (Study 2), and this is specific to women (Study 3).

Objective

A goal of behavioral neuroendocrinology is to understand how basal hormone levels relate to behavior. Studies of human participants sometimes measure self-reported personality traits, in addition to or instead of direct behavioral observation. Although personality traits often predict their respective behaviors, whether personality explains hormone-behavior relationships remains unclear.

Methods

We obtained data from eight previous studies (total N = 985) that examined baseline testosterone and cortisol as predictors of status-relevant behavior (competitiveness, dominance, risk-taking, aggression, affiliation, and social status). We tested whether the previously reported hormone-behavior relationships are mediated by self-reported personality traits (e.g., trait dominance, prestige, extraversion). As a secondary research question, we also tested whether trait dominance moderated the testosterone-behavior relationships.

Results

As expected, self-reported personality traits often predicted status-relevant behaviors, but there was little evidence that traits also correlated with basal testosterone or the testosterone × cortisol interaction. Across all eight studies, personality traits did not significantly mediate hormone-behavior relationships. Indeed, the effect sizes of the hormone-behavior relationships were robust to the inclusion of personality traits as covariates. Further, we did not find strong or consistent evidence that trait dominance moderates the testosterone-behavior association.

Conclusion

Results suggest that basal testosterone and cortisol predict status-related behavior independent of self-reported personality. We discuss how these results may have broader implications for the physiological mechanisms by which testosterone and cortisol influence behavior, a process that could be unconscious and automatic. We also discuss alternative explanations, limitations, and future directions.

Disgust is an emotion that regulates disease avoidance and reduces the likelihood of pathogenic infections. Existing research suggests a bidirectional relationship between disgust and mating, where disgust inhibits sexual behavior and sexual behavior inhibits disgust. In the current study, we investigated the role of individual differences and mating motivations on visual attention to pathogenic cues. Participants (N = 103) were randomly assigned to a mating prime or control condition, and they were asked to view images of pathogenic cues (i.e., rotten food, exposed cuts, bodily fluids) paired with their non-pathogenic counterparts. The findings showed no effect of mating prime on visual attention to pathogenic stimuli; however, dispositional mating strategies (SOI-R) were associated with attention to pathogenic stimuli. Individuals with unrestricted sociosexual orientations viewed pathogenic stimuli longer. The findings demonstrate that dispositional mating orientation is associated with greater attention to disgusting images, a link between pathogens and mating orientation that warrants further exploration.

Immunocompetence can influence an organism’s reproductive fitness, and thus presumably their desirability as a mate (i.e., mate value). In humans, the link between immunocompetence and mate value has found circumstantial support by way of both expressed mate preferences for healthy partners, and via preferences for attractive phenotypes that are ostensibly linked to immune functioning. We examined whether a biological marker of immunocompetence, salivary immunoglobulin A (sIgA), along with self-reported frequency and severity of symptoms of poor health predicted individuals’ reported mate value and mating behavior in a sample of 691 young adults. Our measures of immunocompetence (sIgA and symptoms of poor health) correlated significantly with one another, suggesting sIgA is a viable marker of general immune function in young adults. We then examined the independent contributions of these variables to mate value, controlling for age, sex, and body mass index (BMI). Results showed that sIgA (positively) and poor health (negatively) predicted mate value, but not lifetime number of sex partners or current romantic relationship status. These findings suggest that those with better health and immune function report being more desirable as mating partners but support past research showing null links to reported mating behavior. Together, these findings suggest that more comprehensive work on links between immunocompetence and mating is required.

Objective

Gendered Fitness Interests (GFI) Theory posits that the sex of one’s close kin is a source of variation in socio-political attitudes, especially those concerning sex roles. Drawing on the evolutionary theory of inclusive fitness gained through relatives, it suggests that individuals with greater expected future fitness returns from females will hold more liberal attitudes than those expecting greater future fitness returns from males.

Methods

We examine the effects of various GFI metrics on 11 sex role attitudes across respondents from 42 countries. GFI metrics were the number of kin of each sex, with these same effects discounted by relatedness, residual reproductive value, and both relatedness and residual reproductive value combined. We also examine differences in attitude prediction when examining effects among descendant-only versus all kin, and accounting for emotional closeness and proximity between kin.

Results

Accounting for relatedness and residual reproductive value improved attitude prediction more so than just number of kin. In direct contrast to previous work, individuals with female-biased future fitness interests demonstrated more conservative sex role attitudes. Attitudes did not correlate with an individual’s relative balance of fitness interests from males versus females. Effects were stronger when limiting kin to descendants only (but still not supportive of GFI Theory). Discounting by emotional closeness and proximity did not substantially alter the results, and there was little evidence of effect variation among world regions.

Conclusion

Overall, GFI Theory did not receive convincing support from our findings. We recommend more extensive modelling and empirical testing of GFI theory in order to understand the disparities in support for GFI between studies.

Objective

The Compensatory Prophylaxis Hypothesis proposes that women will show increased pathogen disgust at points in the menstrual cycle when progesterone is high, compensating for the immunosuppressive effects of progesterone. However, evidence for the Compensatory Prophylaxis Hypothesis from studies that used longitudinal designs to investigate whether pathogen disgust tracks changes in progesterone is mixed. It was recently proposed that longitudinal designs may be poorly suited to testing the Compensatory Prophylaxis Hypothesis because carry-over effects when women are tested repeatedly in within-subject designs might obscure the effects of progesterone and pathogen disgust. Consequently, we used a between-subjects design to test for a positive relationship between scores on the pathogen disgust subscale of the Three Domain Disgust Scale and progesterone levels imputed from menstrual cycle data using actuarial tables.

Methods

We employed a between-subject design on N = 1346 women using the Three Domains of Disgust Scale (TDDS).

Results

We found no evidence for a positive effect of progesterone on pathogen disgust, suggesting that null results for the hypothesized relationship between progesterone and pathogen disgust are not limited to studies using designs that may be subject to carry-over effects caused by repeated testing.

Conclusion

Our results add to a growing body of research that does not support the Compensatory Prophylaxis Hypothesis.

Objectives

Despite the aversion to inequality in humans, social hierarchies are a fundamental feature of their social life. Several mechanisms help explain the prevalence of hierarchies over egalitarianism. Recent work has suggested that while people tend to reduce resource inequalities when given the opportunity, they are reluctant to do so when it results in a reversal of social ranks (Xie et al., 2017). In this study, we explore how the way in which hierarchies are established influences this mechanism. We propose that aversion to rank reversal depends on whether rank asymmetry is fair or unfair.

Methods

In an online study, participants read 12 vignettes depicting six hypothetical hierarchies that varied in fairness. In each vignette, one individual was endowed with more resources than another individual, and participants could reduce that inequality by transferring resources from the higher-ranked individual to the lower-ranked one. In half of the vignettes, reducing the inequality led to a reversal of ranks, while in the other half it did not.

Results

We observed that participants were more likely to reverse ranks and reduce inequality when the hierarchy was perceived as unfair.

Conclusion

Overall, our results suggest that considerations of fairness guide participants’ in their decision to reverse ranks.