Adaptive Human Behavior and Physiology最新文献

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.

Facial sexual dimorphism affects observers’ physical dominance ratings. Here, we test whether such perceived dominance influences selective attention. To minimize demand characteristics, we examined whether task-irrelevant masculinized men’s faces would show an attentional bias in several experimental paradigms. Experiment 1 employed a Posner Cueing Paradigm in which participants classified shapes after a masculinized or feminized man’s face was presented. We could not find a difference in participants’ classification speeds when either feminized or masculinized face cued target position. Experiment 2 employed a Flanker Task in which participants judged letter orientation, while ignoring flanking faces. There was no observed difference in participants’ reaction time (RT) when masculinized faces flanked the target. Experiment 3 employed a Dot Probe Task, where participants were presented with a masculinized face and a feminized face to the left and right of center screen, and a target shape was presented in the location of one face. Participants’ task was to classify shape orientation. We observe a small effect of facial sexual dimorphism on participants’ classification speed. In Experiment 4, we primed participants with images meant to induce fear or arousal before each trial of a Dot Probe Task. Following the presentation of a fear inducing picture, participants RT to classify shapes when a masculinized face cued target position did not differ from when a feminized face cued target position. The two different presentation times did not create different patterns of results, indicating that masculinized faces did not induce either a cueing or inhibitory affect. Overall, we failed to support the hypothesis that people selectively attend to masculinized faces when they are presented as irrelevant information.

Objective

Extra-pair mating has potentially severe costs, which favor the evolution of mechanisms that would enable people to reduce them by detecting their partners’ infidelity. Such a mechanism is romantic jealousy, and the current research attempted to examine the interplay between romantic jealousy, personality and the probability of detecting infidelity.

Method

We employed quantitative research methods on a sample of 916 Greek-speaking participants.

Results

we found that higher scorers in romantic jealousy were more likely to detect infidelity than lower scorers. The effect was independent of one’s own infidelity, sex and age. We also found that neuroticism and openness predicted the probability to detect infidelity indirectly through jealousy. More specifically, high scorers in neuroticism experienced stronger jealousy, which in turn, was associated with increased probability to detect infidelity. On the other hand, high scorers in openness experienced lower jealousy that was associated with a decreased probability of detecting infidelity.

Conclusions

Our results were consistent with the hypothesis that the jealousy mechanism has evolved to enable individuals to detect infidelity.

Objective

Organizational hormone effects on the human brain and behavior are often retrospectively assessed via morphological markers of prenatal (e.g., 2D:4D digit ratio) or pubertal (e.g., facial width-to-height ratio, fWHR) hormone exposure. It has been argued that markers should relate to circulating hormones particularly in challenging, dominance/status-relevant situations. However, meta-analytic research indicates that fWHR, a frequently used pubertal marker, is neither reliably sex-dimorphic nor related to steroid hormones. This casts doubt on fWHR’s validity for reflecting hormone levels. Ulna-to-fibula ratio (UFR), an alternative, long-bone-length-based pubertal marker, is sex-dimorphic and associated with dominance motivation. However, its hormonal associations were never tested before. We therefore explored UFR’s relationships to baseline and reactive hormone levels.

Methods

We measured ulna and fibula length as well as shoulder/waist/hip circumference of 81 participants (49 women; after exclusions) via anthropometry. Salivary hormone levels (estradiol, testosterone) at baseline and after a gross-motor one-on-one balancing contest were measured via radioimmunoassay.

Results

We replicated UFR’s dimorphism, unrelatedness to height, and correlations to other putative markers of organizational hormone effects. On an exploratory basis, we found UFR to be related to overall baseline testosterone and to competition-induced reactive surges in steroid hormones (estradiol, testosterone) overall and in women.

Conclusions

Our results hint at UFR’s relationship to baseline testosterone and may indicate functional connections between outcomes of pubertal organizational hormone effects and contest-induced steroid reactivity. Pubertal organizational hormone effects may prepare the endocrine system for dominance and status contests. However, the small sample and the exploratory nature of our research demands replication.

Objective

Social status has been extensively linked to stress and health outcomes. However, two routes by which status can be earned – dominance and prestige – may not uniformly relate to lower stress and better health because of inherent behavioral and stress-exposure differences in these two routes.

Methods

In one exploratory and two preregistered studies, participants (total N = 978) self-reported their trait dominance and prestige and self-reported several stress and health outcomes.

Results

The meta-effects evident across the three studies indicate that higher trait dominance was associated with worse outcomes – higher stress, poorer physical and mental health, poorer behavioral health, poorer life satisfaction, higher negative affect (range of absolute values of non-zero correlations, |r| = [0.074, 0.315], ps < 0.021) – and higher trait prestige was associated with better outcomes – lower stress, better physical and mental health, better behavioral health, better life satisfaction, higher positive and lower negative mood (|r| = [0.134, 0.478], ps < 0.001). These effects remained evident (with few exceptions) after controlling for socioeconomic status, other status-relevant traits, or self-enhancing motives; associations with behavior relevant to the COVID19 pandemic generally were not robust.

Conclusions

This work indicates that evolved traits related to the preferred route by which status is earned likely impact self-reported stress and health outcomes. Future research is necessary to examine physiological and other objective indicators of stress and health in more diverse populations.

Objective

Though it injures the body in many ways, tattooing may also prepare it for later dermal stress through psychoneuroimmunological means.

Methods

To test this, we examined salivary endocrine (cortisol), immune (secretory immunoglobulin A), and inflammatory (C-reactive protein) responses to receiving a new tattoo relative to previous tattoo experience among 48 adults attending a tattoo festival.

Results

We found no effect of previous tattoo experience on pre-posttest cortisol but a significant main effect of extent of previous tattoo experience on pre-posttest cortisol and secretory immunoglobulin A and significant extent of body-by-hour tattooed interaction effect on C-reactive protein.

Conclusions

These findings suggest that the positive psychological evaluation of tattooing as eustress may contribute to biochemical adaptation through tattooing.

Objective

A burgeoning literature inspired by life history theory suggests that psychological and behavioral processes become adaptively calibrated to the levels of harshness and unpredictability encountered in early developmental environments. The current research develops and validates brief scales intended to measure perceptions of childhood harshness (resource scarcity) and unpredictability.

Methods

Data were collected from adults in the U.S. (total N = 3252). Study 1 was used to design the measures and confirm reliability. Study 2 provided evidence of convergent and discriminant validity. Study 3 assessed associations between the perceived harshness and unpredictability scales and indicators of life history strategies.

Results

The scales showed good convergent validity (e.g., moderate-to-strong associations with adverse childhood experiences, impulsivity, and a lack of self-control) and discriminant validity (e.g., null-to-low associations with social desirability, sex, and age), as well as associations with biometric (e.g., age of menarche and sexual debut), behavioral (e.g., number of sexual partners, age of first offspring, number of offspring), and psychometric (e.g., scores on the K-SF-42 and Mini-K) indicators of life history strategies.

Conclusions

These scales provide easy-to-administer retrospective measures of perceived childhood harshness and unpredictability and facilitate research testing hypotheses related to adaptive calibration.

Objective

Findings on the associations between sex hormones and immune function are scarce and mixed, especially in women. To contribute to the understanding on how sex hormones and immune function interact, we analyzed relationships between testosterone, estradiol, and immune responses in women.

Methods

Two doses of hepatitis B vaccine were administered to a group of 55 healthy women. Venous blood samples were collected at three time points: before the first vaccination (time I), one month after the first vaccination (time II), and one month after the second vaccination (time III), to quantify sex hormone levels (i.e., testosterone and estradiol) and the production of antibodies in response to the hepatitis B vaccinations.

Results

Women’s immune response (i.e., the production of hepatitis B antibodies) was negatively associated with testosterone levels one month after the first vaccination and positively associated with estradiol levels one month after the second vaccination. A decrease in testosterone levels between time II and time III was also observed. No differences in estradiol levels over time were found.

Conclusion

Our results demonstrate negative associations between testosterone and immune responses in women as previously described for males of several animal species, including humans. There were also positive associations between estradiol and immune responses, highlighting the immunomodulatory role of sex hormones in women. Potential bidirectional effects between immune markers and sex hormones are discussed.

Biological differences between men and women mandate that women’s obligatory investment in reproduction is significantly greater than that of men. As a result, women have evolved to be the “choosier” of the two sexes and men have evolved to compete for female choice. To the degree that overconfidence is an effective tool for attracting mates and driving away competitors, greater competition among men suggests that they should express more overconfidence than women. Thus, sexual selection may be the primary reason why overconfidence is typically more pronounced in men than it is in women. Sexual selection may also be a distal, causal factor in what we describe as a cult of overconfidence pervading modern organizations and institutions. Whereas overconfidence was once regulated and constrained by features of ancestral life, levels of social mobility and accountability in contemporary society and modern organizations make it increasingly difficult to keep this gendered bias in check.

Objective

A growing body of research has begun investigating the relationship between hormones and female competitiveness. Many researchers have focused on the effect of the menstrual cycle and hormonal contraceptives. Despite many attempts at understanding hormone-behavior associations, contradictory findings have made it difficult to determine the existence of true effects. The aim of the current research was to use a robust methodological design to investigate the effect of fertility probability on four competitive orientations in naturally cycling women and hormonal contraceptive users.

Methods

Using a longitudinal diary study with over 3,900 observations from 21 countries, we explore the effect of fertility probability on four self-report competitive orientations after controlling for menstruation: self-developmental competition, hyper competitiveness, competition avoidance, and lack of interest toward competition.

Results

Using Bayesian estimation for ordinal mixed models, we found that fertility probability was associated with an increase in self-development competitiveness amongst naturally cycling women but not hormonal contraceptive users. We also found weak evidence that hormonal contraceptive users show reduced interest in competing compared to naturally cycling women. There were no other robust effects of fertility or hormonal contraceptive use.

Conclusions

These results suggest that fertility probability is associated with increased fluctuations in self-development competitive motivation and that hormonal contraceptives interfere with this effect. This research contributes to the growing body of literature suggesting that hormonal contraceptives may influence psychology and behavior by disrupting evolved hormonal mechanisms.