Sex Differences In Behavior Research Articles

Relating sex differences in aggression to three forms of empathy

Men commit violent crime at substantially higher rates than women. One proposed mediator of this relation is empathy, as men consistently score lower than women on measures of empathy and empathy deficits are thought to characterize violent crime and disorders of aggression. However, recent research suggests that traditional empathy measures are only weakly related to aggression, whereas a new form of “anti-empathy” exhibits much stronger relations. The goal of this study was to investigate the extent to which empathy and anti-empathy indirectly account for sex differences in aggression and antisocial behavior, and whether these relations differ by sex. The current study (N = 369) employed a multifaceted measure of empathy to show that sex differences in aggression were indirectly accounted for by affective empathy and anti-empathy, but not cognitive empathy. The effects of empathy deficits were equivalent for men and women. These findings provide support for empathy as an important and generalizable trait in the sex-aggression association and highlight the usefulness of a focus on specific affective forms.

Estradiol rapidly modulates excitatory synapse properties in a sex- and region-specific manner in rat nucleus accumbens core and caudate-putamen.

Estradiol acutely facilitates sex differences in striatum-dependent behaviors. However, little is understood regarding the underlying mechanism. In striatal regions in adult rodents, estrogen receptors feature exclusively extranuclear expression, suggesting that estradiol rapidly modulates striatal neurons. We tested the hypothesis that estradiol rapidly modulates excitatory synapse properties onto medium spiny neurons (MSNs) of two striatal regions, the nucleus accumbens core and caudate-putamen in adult female and male rats. We predicted there would be sex-specific differences in pre- and postsynaptic locus and sensitivity. We further analyzed whether MSN intrinsic properties are predictive of estrogen sensitivity. Estradiol exhibited sex-specific acute effects in the nucleus accumbens core: miniature excitatory postsynaptic current (mEPSC) frequency robustly decreased in response to estradiol in female MSNs, and mEPSC amplitude moderately increased in response to estradiol in both male and female MSNs. This increase in mEPSC amplitude is associated with MSNs featuring increased intrinsic excitability. No MSN intrinsic electrical property associated with changes in mEPSC frequency. Estradiol did not acutely modulate mEPSC properties in the caudate-putamen of either sex. This is the first demonstration of acute estradiol action on MSN excitatory synapse function. This demonstration of sex and striatal region-specific acute estradiol neuromodulation revises our understanding of sex hormone action on striatal physiology and resulting behaviors.NEW & NOTEWORTHY This study is the first to demonstrate rapid estradiol neuromodulation of glutamatergic signaling on medium spiny neurons (MSNs), the major output neuron of the striatum. These findings emphasize that sex is a significant biological variable both in MSN sensitivity to estradiol and in pre- and postsynaptic mechanisms of glutamatergic signaling. MSNs in different regions exhibit diverse responses to estradiol. Sex- and region-specific estradiol-induced changes to excitatory signaling on MSNs explain sex differences partially underlying striatum-mediated behaviors and diseases.

A meta-analysis of sex differences in human navigation skills.

There are inconsistent reports regarding behavioral sex differences in the human navigation literature. This meta-analysis quantifies the overall magnitude of sex differences in large-scale navigation skills in a variety of paradigms and populations, and examines potential moderators, using 694 effect sizes from 266 studies and a multilevel analytic approach. Overall, male participants outperform female participants, with a small to medium effect size (d = 0.34 to 0.38). The type of task, the type of dependent variable and the testing environment significantly contribute to variability in effect sizes, although there are only a few situations in which differences are either nonexistent or very large. Pointing and recall tasks (and the deviation scores associated with them) show larger sex differences than distance estimation tasks or learning to criterion. Studies with children younger than 13 years showed much smaller effect sizes (d = .15) than older age groups. We discuss the implications of these findings for understanding sex differences in human spatial navigation and identify avenues for future navigation research.

Prenatal and childhood exposure to chlordecone and sex-typed toy preference of 7-year-old Guadeloupean children

Chlordecone was used intensively as an insecticide in the French West Indies. Because of its high persistence, the resulting contamination of food and water has led to chronic exposure of the general population as evidenced by its presence in the blood of people of Guadeloupe, in particular in pregnant women and newborns, and in maternal breast milk. Chlordecone is recognized as a reproductive and developmental toxicant, is neurotoxic and carcinogenic in rodents, and is considered as an endocrine-disrupting compound with well-established estrogenic and progestogenic properties both in vitro and in vivo. The question arises of its potential consequences on child neurodevelopment following prenatal and childhood exposure, in particular on behavioral sexual dimorphism in childhood. We followed 116 children from the TIMOUN mother-child cohort study in Guadeloupe, who were examined at age 7. These children were invited to participate in a 7-min structured play session in which they could choose between different toys considered as feminine, masculine, or neutral. The play session was video recorded, and the percentage of the time spent playing with feminine or masculine toys was calculated. We estimated associations between playtime and prenatal exposure to chlordecone (assessed by concentration in cord blood) or childhood exposure (determined from concentrations in child blood obtained at the 7-year follow-up), taking into account confounders and co-exposures to other environmental chemicals. We used a two-group regression model to take into account sex differences in play behavior. Our results do not indicate any modification in sex-typed toy preference among 7-year-old children in relation with either prenatal or childhood exposure to chlordecone.

Effects of body size, sex, parental care and moult strategies on auk diving behaviour outside the breeding season

Information on seabird foraging behaviour outside the breeding season is currently limited. This knowledge gap is critical as this period is energetically demanding due to post‐fledging parental care, feather moult and changing environmental conditions. Based on species’ body size, post‐fledging parental strategy and primary moult schedule we tested predictions for key aspects of foraging behaviour (maximum dive depth (MDD), daily time submerged (DTS) and diurnal dive activity (DDA)) using dive depth data collected from three seabird species (common guillemot Uria aalge, razorbill Alca torda and Atlantic puffin Fratercula arctica) from the end of the breeding season (July) to mid‐winter (January). We found partial support for predictions associated with body size; guillemots had greater MDD than razorbills but MDD did not differ between razorbills and puffins, despite the former being 35% heavier. In accordance with sexual monomorphism in all three species, MDD did not differ overall between the sexes. However, in guillemots and razorbills there were sex‐specific differences, such that male guillemots made deeper dives than females, and males of both species had higher DTS. In contrast, there were no marked sex differences in dive behaviour of puffins in July and August in accordance with their lack of post‐fledging parental care and variable moult schedule. We found support for the prediction that diving effort would be greater in mid‐winter compared to the period after the breeding season. Despite reduced daylight in mid‐winter, this increase in DTS occurred predominantly during the day and only guillemots appeared to dive nocturnally to any great extent. In comparison to diving behaviour of these species recorded during the breeding season, MDD was shallower and DTS was greater during the non‐breeding period. Such differences in diving behaviour during the post‐breeding period are relevant when identifying potential energetic bottlenecks, known to be key drivers of seabird population dynamics.

Sex differences in behavior and neuropharmacology of zebrafish.

Sex is an important variable in biomedical research. The zebrafish (Danio rerio) is increasingly utilized as a powerful new model organism in translational neuroscience and pharmacology. Mounting evidence indicates important sex differences in zebrafish behavioral and neuropharmacological responses. Here, we discuss the role of sex in zebrafish central nervous system (CNS) models, their molecular mechanisms, recent findings and the existing challenges in this field. We also emphasize the growing utility of zebrafish models in translational neuropharmacological research of sex differences, fostering future CNS drug discovery and the search for novel sex-specific therapies. Finally, we highlight the interplay between sex and environment in zebrafish models of sex-environment correlations as an important strategy of CNS disease modeling using this aquatic organism.

Hybridization in human evolution: Insights from other organisms.

During the late Pleistocene, isolated lineages of hominins exchanged genes thus influencing genomic variation in humans in both the past and present. However, the dynamics of this genetic exchange and associated phenotypic consequences through time remain poorly understood. Gene exchange across divergent lineages can result in myriad outcomes arising from these dynamics and the environmental conditions under which it occurs. Here we draw from our collective research across various organisms, illustrating some of the ways in which gene exchange can structure genomic/phenotypic diversity within/among species. We present a range of examples relevant to questions about the evolution of hominins. These examples are not meant to be exhaustive, but rather illustrative of the diverse evolutionary causes/consequences of hybridization, highlighting potential drivers of human evolution in the context of hybridization including: influences on adaptive evolution, climate change, developmental systems, sex-differences in behavior, Haldane's rule and the large X-effect, and transgressive phenotypic variation.

Sex differences in depressive-like behaviour may relate to imbalance of microglia activation in the hippocampus

As is reported, the incidence and prevalence of depression are higher in women than in men, but the cause of this sex difference remains elusive. Although recent studies implicated that over-activated microglia played a crucial role in depression, whether hippocampal microglia associates with the sex difference of depressive-like behaviours is intriguing. In the present study, both male and female mice were subjected to chronic unpredictable mild stress (CUMS) for 4 weeks. Behavioural tests were performed to evaluate depressive-like phenotypes, while several microglia-related biomarkers and neurotrophic factor in hippocampi were detected to analyse sex difference. As a result, CUMS interfered with the body weight gain, sucrose preference and spontaneous activity in mice of both sexes. However, this effect tended to be more impressive in females. Generally, hippocampal microglia were activated regardless of sex, but the expressions of pro- and anti-inflammatory factors induced by CUMS were sex-specific. Chronic stress increased hippocampal iNOS and IL-1β mRNA levels only in male mice, while upregulated TNF-α mRNA just in females. Meanwhile, the expressions of hippocampal IL-10, Arg-1 and IL-1ra were all downregulated in CUMS females rather than males. In addition, though the ratios of the pro- vs. anti-inflammatory cytokines elevated after the stress paradigm in both sexes, we noticed more remarkable trends in female mice regarding TNF-α/IL-10 and iNOS/Arg-1. This discovery suggested that females were inclined to be more pro-inflammatory after stress. Afterwards, we observed that the expressions of BDNF and its receptor TrkB in hippocampus decreased greater in female compared to male mice when facing stress stimulations. Furthermore, the depressive-like behaviours were correlated to BDNF mRNA quantities in both sex mice, and there was also a sex-specific relationship between BDNF and hippocampal microglia-related inflammatory biomarkers. Collectively, our study speculated that the imbalance of microglial pro- and anti-inflammatory states as well as the BDNF-TrkB-dependent pathway in hippocampus is involved in the depressive-like behaviours. The “microglia-neuroinflammation-BDNF” interconnection may be a fundamental mechanism for sex differences in depression.

Active anti-predator behaviour of red titi monkeys (Plecturocebus cupreus).

Due to their inconspicuous behaviour and colouration, it has been assumed that titi monkeys' main anti-predator behaviour is passive crypsis and hiding. So far, active predator mobbing has been documented only for black-fronted titi monkeys, Callicebus nigrifrons. Here we report for the first time mobbing behaviour of red titi monkeys, Plecturocebus cupreus (previously Callicebus cupreus), as reaction to an ocelot (Leopardus pardalis) and a Boa constrictor. We also report other active anti-predator behaviours, such as alarm calling and approaching, as reactions to tayras (Eira barbara) and raptors. Our observations provide additional evidence for sex differences in anti-predator behaviour, possibly related to the evolution and maintenance of social monogamy.

Self-Reported Male-Female Differences in Criminal Involvement Do Not Account for Criminal Justice Processing Differences

Disparities between males and females in criminal behavior have been widely documented. Despite the extensive amount of research examining sex differences in criminal and analogous behaviors, there is no consensus on whether self-reported misbehavior accounts for the large sex differences found in all phases of the criminal justice system. The current study explores whether, and to what degree, self-reported misconduct accounts for male-female differences. To do so, data drawn from the National Longitudinal Study of Adolescent to Adult Health (Add Health) were analyzed. Consistent with prior research, the results revealed statistically significant and substantively large male-female differences in being arrested, pleading guilty, being sentenced to probation, and being incarcerated. These disparities were unaffected by self-reports of lifetime violent behavior, lifetime non-violent behavior, low self-control, IQ, parental socialization, and social support.

Signatures of sex: Sex differences in gene expression in the vertebrate brain.

Women and men differ in disease prevalence, symptoms, and progression rates for many psychiatric and neurological disorders. As more preclinical studies include both sexes in experimental design, an increasing number of sex differences in physiology and behavior have been reported. In the brain, sex-typical behaviors are thought to result from sex-specific patterns of neural activity in response to the same sensory stimulus or context. These differential firing patterns likely arise as a consequence of underlying anatomic or molecular sex differences. Accordingly, gene expression in the brains of females and males has been extensively investigated, with the goal of identifying biological pathways that specify or modulate sex differences in brain function. However, there is surprisingly little consensus on sex-biased genes across studies and only a handful of robust candidates have been pursued in the follow-up experiments. Furthermore, it is not known how or when sex-biased gene expression originates, as few studies have been performed in the developing brain. Here we integrate molecular genetic and neural circuit perspectives to provide a conceptual framework of how sex differences in gene expression can arise in the brain. We detail mechanisms of gene regulation by steroid hormones, highlight landmark studies in rodents and humans, identify emerging themes, and offer recommendations for future research. This article is categorized under: Nervous System Development > Vertebrates: General Principles Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms Gene Expression and Transcriptional Hierarchies > Sex Determination.

Does personality mediate the relationship between sex and environmentalism?

The finding that females hold more pro-environmental attitudes and engage in more conservation behavior, relative to males, is one of the most robust effects in the field of environmental psychology. Yet sparse research has attempted to understand why males are less pro-environmental than females. In three studies, the present research tested the hypothesis that sex differences in personality account for sex (Studies 1–3) and gender (Study 3) differences in both pro-environmental attitudes and behavior. Results from Study 1 demonstrated that conscientiousness mediated links between sex and attitudes towards environmental utilization, protectionism, and conservation behavior in an undergraduate sample. Results from Study 2 with a community sample demonstrated that conscientiousness, agreeableness, and neuroticism mediated the link between sex and environmental protectionism. Study 3 replicated the mediating effect of conscientiousness on sex differences in environmental behavior using the HEXACO model and extended this finding beyond biological sex to gender differences. Taken together, results suggest that core differences in personality traits explain sex and gender differences in environmentalism, offering new insight into how to potentially promote increased pro-environmental action among men.

Sexual dimorphism in the physiological response of the Apoe −/− atherosclerosis model to sleep fragmentation

Abstract Sleep fragmentation (SF) is tightly correlated with the development of chronic low grade inflammatory diseases such as, type 2 diabetes and atherosclerosis; however, the exact relationship between SF and atherogenesis is unknown. Little evidence exists regarding the origin of sex differences in sleep behavior. While the role of gender has been studied in atherosclerosis, the impact of gender in SF-associated atherogenesis is not known. Recently, we have shown that high fat diet (HFD) fed male Apolipoprotein E-deficient (Apoe−/−)mice on SF unexpectedly experienced premature death, with 80% of males not surviving past week 2 of SF, while 80% of females survived past week 8 under the same conditions. To investigate the gender effects, male and female Apoe−/− mice were fed a HFD and SF for 10 days. Following HFD and SF, male mice, but not female Apoe−/− mice had enlarged hearts and lymph nodes, as well as peritoneal bleeding. Further, SF resulted in a significantly higher amount of circulating LPS and alterations in the immune composition of bone marrow (BM), blood, and lymph nodes (LN) in male HFD fed Apoe−/− mice vs SF female Apoe−/− mice. We detected a significant decrease in myeloid cells in the BM and blood, as well as a decrease in the percentage of T and B cells in the LN of HFD fed-SF males’ vs diet matched SF females. Interestingly, when male Apoe−/− mice were administered 17b-estradiol orally, in supplement with HFD feeding and SF, they survived past the 14 day death window. Altogether, SF alters the immune response in male atherosclerotic Apoe−/− mice resulting in early death. Our data suggests that the hormonal landscape in female Apoe−/− mice protects against SF-induced premature death via estrogen-dependent mechanisms.

Gender-related differences in care-seeking behaviour for newborns: a systematic review of the evidence in South Asia

IntroductionData indicate substantial excess mortality among female neonates in South Asia compared with males. We reviewed evidence on sex and gender differences in care-seeking behaviour for neonates as a driver...

Sex differences in the expression of morphine withdrawal symptoms and associated activity in the tail of the ventral tegmental area

Recent studies, in male rodents, have begun to elucidate a role for the GABAergic neurons in the tail of the ventral tegmental area (tVTA) in morphine withdrawal. To date, the mechanisms underlying morphine withdrawal have been studied almost exclusively in male animals. As a result, there is a considerable gap in our current understanding of the processes underlying sex differences in morphine withdrawal behaviors and its effects on cellular activity in the tVTA in females. The purpose of the present study was to investigate the influence of sex on the expression and duration of spontaneous somatic morphine withdrawal syndrome, and to characterize the relationship between spontaneous somatic withdrawal symptoms and cellular activation (measured as phosphorylated CREB; pCREB), in the GABAergic tVTA in male and female rats. Morphine-dependent adult male and female Long Evans rats underwent 72 h of spontaneous withdrawal, and somatic withdrawal symptoms were assessed every 12 h. Male morphine-dependent rats expressed more severe symptoms during the early phases of withdrawal compared to females. Although, females demonstrated lower overall symptom severity, their symptoms persisted for a longer period of time, thus demonstrating higher withdrawal-symptom severity than males during late withdrawal. pCREB activity in the tVTA was elevated in morphine-withdrawn rats and was positively correlated with the severity of withdrawal symptoms. These results demonstrate sex differences in the timing of the expression of somatic withdrawal. Our data add to the growing body of evidence demonstrating a role for the tVTA in morphine withdrawal and begin to establish a sex-dependent behavioral and molecular profile within this brain region.

Sexually Dimorphic Regulation of Behavioral States by Dopamine in Caenorhabditis elegans.

Sex differences in behavior allow animals to effectively mate and reproduce. However, the mechanism by which biological sex regulates behavioral states, which underlie the regulation of sex-shared behaviors, such as locomotion, is largely unknown. In this study, we studied sex differences in the behavioral states of Caenorhabditis elegans and found that males spend less time in a low locomotor activity state than hermaphrodites and that dopamine generates this sex difference. In males, dopamine reduces the low activity state by acting in the same pathway as polycystic kidney disease-related genes that function in male-specific neurons. In hermaphrodites, dopamine increases the low activity state by suppression of octopamine signaling in the sex-shared SIA neurons, which have reduced responsiveness to octopamine in males. Furthermore, dopamine promotes exploration both inside and outside of bacterial lawn (the food source) in males and suppresses it in hermaphrodites. These results demonstrate that sexually dimorphic signaling allows the same neuromodulator to promote adaptive behavior for each sex.SIGNIFICANCE STATEMENT The mechanisms that generate sex differences in sex-shared behaviors, including locomotion, are not well understood. We show that there are sex differences in the regulation of behavioral states in the model animal Caenorhabditis elegans Dopamine promotes the high locomotor activity state in males, which must search for mates to reproduce, and suppresses it in self-fertilizing hermaphrodites through distinct molecular mechanisms. This study demonstrates that sex-specific signaling generates sex differences in the regulation of behavioral states, which in turn modulates the locomotor activity to suit reproduction for each sex.

Sex differences in pollinator behavior: Patterns across species and consequences for the mutualism.

Intraspecific variation in floral visitor behaviour and pollination efficiency has been much less studied than interspecific variation. Nevertheless, it is clear that large differences in these traits exist within species, and in particular between sexes within species. With the exception of a few well-studied interactions, however, the consequences of these differences in the pollinators and visited plants remain to be investigated. In this review, we document large and consistent differences in the foraging patterns of male and female pollinators that have been demonstrated to directly affect plant reproduction or that have clear potential to do so. Males and females differ in visitation frequency, type of flowers visited, and per-visit pollen transfer. Females gather more and different resources from flowers compared to males, and males generally tend to show more mobile foraging patterns than females. We argue that these sex-associated patterns have broad generality across pollinators, and that sex-associated differences can in some cases be larger than differences between species. We offer predictions about how these patterns will influence pollinator preference, specialization, and fidelity, as well as the cost, quality and quantity of pollination service to plants. In the face of increasing threats to plant-pollinator interactions, understanding their basic functioning and the variation inherent in their component parts is critical. We advocate for more attention to sex-based differences among pollinators in particular, and the consequences of intraspecific variation more broadly.

Sex differences in fear regulation and reward-seeking behaviors in a fear-safety-reward discrimination task

Reward availability and the potential for danger or safety potently regulate emotion. Despite women being more likely than men to develop emotion dysregulation disorders, there are comparatively few studies investigating fear, safety and reward regulation in females. Here, we show that female Long Evans rats did not suppress conditioned freezing in the presence of a safety cue, nor did they extinguish their freezing response, whereas males did both. Females were also more reward responsive during the reward cue until the first footshock exposure, at which point there were no sex differences in reward seeking to the reward cue. Darting analyses suggest females were able to regulate this behavior in response to the safety cue, suggesting they were able to discriminate between fear and safety cues but did not demonstrate this with conditioned suppression of freezing behavior. However, levels of darting in this study were too low to make any definitive conclusions. In summary, females showed a significantly different behavioral profile than males in a task that tested the ability to discriminate among fear, safety and reward cues. This paradigm offers a great opportunity to test for mechanisms that are generating these behavioral sex differences in learned safety and reward seeking.

How should we understand the absence of sex differences in the genetic and environmental origins of antisocial behavior?

Available twin-family data on sex differences in antisocial behavior (ASB) simultaneously suggest that ASB is far more prevalent in males than in females, and that its etiology (i.e. the effects of genes, environments, hormones, culture) does not differ across sex. This duality presents a conundrum: How do we make sense of mean sex differences in ASB if not via differences in genes, environments, hormones, and/or cultures? The current selective review and critique explores possible contributions to these seemingly incompatible sets of findings. We asked whether the presence of sex differences in behavior could be smaller than is typically assumed, or confined to a specific set of behaviors. We also asked whether there might be undetected differences in etiology across sex in twin-family studies. We found little evidence that bias or measurement invariance across sex account for phenotypic sex differences in ASB, but we did identify some key limitations to current twin-family approaches. These included the questionable ability of qualitative sex difference analyses to detect gender norms and prenatal exposure to testosterone, and concerns regarding specific analytic components of quantitative sex difference analyses. We conclude that the male preponderance in ASB is likely to reflect a true sex difference in observed behavior. It was less clear, however, that the genetic and environmental contributions to ASB are indeed identical across sex, as argued by prior twin-family studies. It is our hope that this review will inspire the development of new, genetically-informed methods for studying sex differences in etiology.

Sex and the Single Fly: A Perspective on the Career of Bruce S. Baker.

Bruce Baker, a preeminent Drosophila geneticist who made fundamental contributions to our understanding of the molecular genetic basis of sex differences, passed away July 1, 2018 at the age of 72. Members of Bruce's laboratory remember him as an intensely dedicated, rigorous, creative, deep-thinking, and fearless scientist. His trainees also remember his strong commitment to teaching students at every level. Bruce's career studying sex differences had three major epochs, where the laboratory was focused on: (1) sex determination and dosage compensation, (2) the development of sex-specific structures, and (3) the molecular genetic basis for sex differences in behavior. Several members of the Baker laboratory have come together to honor Bruce by highlighting some of the laboratory's major scientific contributions in these areas.