Human Nature-An Interdisciplinary Biosocial Perspective最新文献

The self-domestication hypothesis has made significant contributions to our thinking about hominin evolution and ecology. It has struggled, however, to find compelling and testable causes of reductions in hominin aggression and violent behavior. This paper examines variability among hominin mating systems and imbalances in operation sex ratios (OSRs) as a potential factor influencing levels of aggression resulting from male intrasexual competition, i.e., male-male competitive aggression. This paper uses multivariate generalized linear modeling (GLM) to examine data from modern hunter-gatherer societies having to do with the causes and consequences of OSR imbalances (as reflected by levels of polygamy) and male intrasexual competition. This paper focuses especially on the role of population density as a potential source of OSR variability. This paper shows that population density correlates strongly with hunter-gatherer OSRs and that this relationship remains strong when controlling for the effects of other potentially intercorrelated variables. This paper shows that, among modern hunter-gatherers, lower population densities lead to greater imbalances in terms of OSRs and therefore higher levels of male-male aggression. This implies high levels of male intrasexual competition among early hominins given likely conditions of very low population densities. The paper closes by proposing some strategies for investigating hominin demographic patterning prehistorically and predicting OSR imbalances, as well as intrasexual competition, based on that information.

In four pre-registered studies, we tested implications from a cooperation model that explains victim-blaming and victim-devaluation as the result of cooperation dilemmas, as a way for people to avoid the costs of helping victims (who seem to be unpromising cooperation partners) without paying the reputational cost of being seen as ungenerous, reluctant cooperators. An implication of this perspective is that, if a victim of misfortune is seen as imposing costs on others by requesting help (as opposed to bearing the costs), they will be seen as persons of low character, avoided as future cooperators, and deemed responsible for their misfortune (seen as negligent). The four studies presented here support these predictions. The effect is not confounded by familiar or social obligations, as it occurs in the same way when the targets, from whom help is requested, are the victim's parents, siblings, best friends or communities. Contrary to expectations, negligence attributions were not modulated by the victim's being described as poor (in need of help) or rich (not in need).

Previous work has suggested that males and females adopt different exploration styles, with females often taking a more secure, or cautious exploration approach. However, exploration behavior is multi-faceted, and previous studies often investigated only specific aspects of it. As a result, sex differences in exploration remain vaguely defined, and it currently remains unclear when differences develop. In the current study, females (n = 206) and males (n = 218) aged 7-77 years explored a 3D virtual environment. First, we computed a series of exploration measures that are commonly used in the animal literature (including roaming entropy, distance traveled, shape of exploration and exploratory efficiency). Taking a fine-grained approach, based on a hierarchical cluster analysis we identified three distinct measures of exploration: (1) Exploratory activity; (2) Exploratory efficiency; (3) Shape of exploration. We investigated whether these distinct aspects capture individual differences- between sexes and across the lifespan- in exploration behavior. Males were found to explore more than females, as evidenced by higher exploratory activity and a more complex shape of exploration. Interestingly, however, females explored more efficiently than males. No interaction between age and sex was observed, suggesting that the effect remains stable across the lifespan. These findings suggest that even though women show more caution when exploring an unknown environment, they are more efficient in charting it. Our novel fine-grained exploratory behavior analyses further suggested that older individuals had a simpler exploration shape- as defined by lower sinuosity/tortuosity in their path- than younger individuals, while other exploration measures were not affected by age. The current novel findings thus suggest that specific characteristics of exploration behavior depend on individual differences, including sex and age. Previous work has suggested that exploration behavior is affected in several neuropsychiatric disorders (e.g., in schizophrenia), and our measures of exploration could potentially be used to characterize unique aspects of these disorders, and serve as cognitive markers.

Global constructs such as the general factor of personality (GFP), trait emotional intelligence (TEI), and the K-factor have generated considerable interest as well as controversy in evolutionary psychology. Research employing exploratory structural equation modeling (ESEM) suggests higher-order factors may be attributable to the omission of cross-loadings from confirmatory factor models and scale score computation, which can upwardly bias first-order factor and scale score correlations. In the current project, we conducted two studies to determine if GFP and TEI are method artifacts using national random-digit-dialing (n = 1,805) and teacher (n = 331) samples, respectively. We also conducted a study examining the possibility that K is an artifact using a sample of college students (n = 661). Using ESEM and bifactor ESEM to allow cross-loadings, we found evidence suggesting a general factor did not subsume all the Big Five personality traits and concluded that GFP is likely an artifact of omitted cross-loading bias. Evidence of global K and TEI factors survived free estimation of cross-loadings, and findings suggest total TEI scores may be sufficient; however, model-based reliability was too low to warrant the use of total Mini-K scores. Researchers should consider using ESEM to examine the internal structures of their scales at the item level before computing total scale scores.

To gain support, children use signals to communicate their needs and wants to parents. Infant signals of need, particularly infant cries, have been extensively studied in diverse populations. However, the full range of potential child signals of need, which extend beyond cries, has rarely been investigated in a single study of children of all ages. To help fill this gap, we collected mother and other primary caregiver reports of three common types of child signaling from 131 families with 263 children on Utila, a small island off the coast of Honduras. In exploratory analyses, we found that child signaling was common in both sexes and across all ages, although it decreased with age and neighborhood quality and increased with the frequency of conflict between children and caretakers. Consistent with signaling theory, children who were sad more frequently were perceived as needier within the household and were more likely to receive investment. Caregivers were less likely to respond positively in situations of family conflict or child transgressions, and more likely for injuries and illness. Our results suggest that evolutionary theories of signaling can help explain patterns of child sadness, crying, and temper tantrums.

This study examines the impact of pre-moder wars on sex ratios at birth. Specifically, it investigates whether wars involving premodern weaponry and more limited destruction increased stress for pregnant women such that the resulting hormonal changes in their bodies may have led to a decrease in the ratio of live-born boys to girls. To address this question, we analyzed all baptismal records from the Basque Country during the 19th century, encompassing nearly 1.2 million individuals. Our findings confirm that the First Carlist War (1833-1840) exercised the most significant demographic impact on the region. However, all wars resulted in variations in demographic behavior, reducing in sex ratios at birth by around 1%. This effect is even more pronounced when focusing on the main conflict zones, where sieges and major battles took place, leading to an impact of 3.2%. The effect was not only immediately visible in sex ratios at birth but became particularly evident during the first three months after the events. Furthermore, prolonged battles were found to have the most substantial influence, with an average effect during the three months after the battle of almost 7% on sex ratios at birth. In conclusion, our study demonstrates that premodern wars reduced sex ratios at birth.

We review recent experimental studies relevant to assess the proposal that human infants possess a sense of fairness that relies on sociomoral knowledge. We propose that this knowledge may include a core concept of justice with four foundational aspects: impartiality, agency, obligatoriness and conflicting claims. Infants' and toddlers' looking times, manual preferences and spontaneous actions provide some evidence for the first three features. Very early-emerging sociomoral evaluations and expectations about resource distributions show that infants process morally relevant information about distributors and recipients, suggesting that they are sensitive to the agency and impartiality constraints. Early evaluations appear to be linked to third-party expressions of praise or admonishment and to the deliverance of rewards and punishment, providing initial support for the obligatoriness constraint. More work is needed to investigate the sensitivity to conflicting claims, to assess the universality of early emerging evaluation skills and to show how core concepts relate to the development of explicit judgments and beliefs about duties and rights.

Despite decades of research on the emergence of human speech capacities, an integrative account consistent with hominin evolution remains lacking. We review paleoanthropological and archaeological findings in search of a timeline for the emergence of modern human articulatory morphological features. Our synthesis shows that several behavioral innovations coincide with morphological changes to the would-be speech articulators. We find that significant reductions of the mandible and masticatory muscles and vocal tract anatomy coincide in the hominin fossil record with the incorporation of processed and (ultimately) cooked food, the appearance and development of rudimentary stone tools, increases in brain size, and likely changes to social life and organization. Many changes are likely mutually reinforcing; for example, gracilization of the hominin mandible may have been maintainable in the lineage because food processing had already been outsourced to the hands and stone tools, reducing selection pressures for robust mandibles in the process. We highlight correlates of the evolution of craniofacial and vocal tract features in the hominin lineage and outline a timeline by which our ancestors became 'pre-adapted' for the evolution of fully modern human speech.

Intimate relationships are frequently characterized by problems, which the current research aimed to identify. We first proposed an evolutionary theoretical framework to understand the nature of intimate relationship problems. Subsequently, we employed a mixed-methods approach to identify these problems. In particular, Study 1 used a combination of qualitative research methods on a sample of 258 Greek-speaking participants and identified 153 relationship problems. Study 2 used quantitative research methods on a sample of 783 Greek-speaking participants and classified them into 14 broader categories. The most common problems were a poor sex life, followed by incompatibility and neglect. Other common problems included a partner's bad character, fear of abandonment, and lack of shared fun and recreation. Lack of loyalty and respect, disagreement over family planning, and privacy invasion were the least common problems in our sample. Both sexes reported similar problems, while the length of the relationship was not significantly associated with the presence of different relationship problems. Additionally, participants' age, children, cohabitation, and relationship status were associated with some of the identified relationship problems.

Automatic behavioral matching includes Rapid Facial Mimicry (RFM) and Yawn Contagion (YC) that occur when the facial expression of an individual acts as a 'mirror social releaser' and induces the same facial expression in the observer (within 1 s for RFM, and minutes for YC). Motor replication has been linked to coordination and emotional contagion, a basic form of empathy. We investigated the presence and modulating factors of Rapid Smile Mimicry (RSM) and YC in infants/toddlers from 10 to 36 months at the nursery 'Melis' (Turin, Italy). In February-May 2022, we gathered audio and/or video of all occurrences data on affiliative behaviors, smiling during play, and yawning during everyday activities. Both RSM and YC were present, as toddlers were most likely to smile (within 1 s) or yawn (within three-min) after perceiving a smile/yawn from another toddler. Sex, age, and parents' country of origin did not influence RSM and YC occurrence, probably because gonadal maturation was long to come, the age range was skewed towards the early developmental phase, and toddlers had been in the same social group for months. RSM and YC showed social modulation, thus possibly implying more than just motor resonance. Both phenomena were inversely related to affiliation levels (a social bond proxy). Because literature reports that in adults RSM and YC may increase with familiarity, our reversed result suggests that in certain toddler cohorts the same phenomena may help increase socio-emotional coordination and that the function of motoric resonance may be experience- and context-dependent.