Suppression of ovarian hormones in adolescent rats has no effect on anxiety-like behaviour or c-fos activation in the amygdala.

In humans, sex differences in mood disorders emerge during adolescence, with prevalence rates being consistently higher in females than males. It has been hypothesised that exposure to endogenous ovarian hormones during adolescence enhances the susceptibility of females to mood disorders from this stage of life onwards. However, experimental evidence in favour of this hypothesis is lacking.

Gender Equality and Gender Gaps in Mathematics Performance.

In a recent analysis of mathematics performance (Eriksson et al. 2020), national gender egalitarian values were positively associated with an increase in the average mathematics scores of high-school boys relative to girls. This study highlights that progressive gender egalitarian values at a national level might not translate into equality of opportunity at an individual level.

Social experience during adolescence in female rats increases 50 kHz ultrasonic vocalizations in adulthood, without affecting anxiety-like behavior.

Adolescents are highly motivated to engage in social interactions, and researchers have hypothesized that positive social relationships during adolescence can have long term, beneficial effects on stress reactivity and mental well-being. Studies of laboratory rodents provide the opportunity to investigate the relationship between early social experiences and later behavioral and physiological responses to stressors. In this study, female Lister-hooded rats (N = 12 per group) were either (a) provided with short, daily encounters (10 min/day) with a novel partner during mid-adolescence (postnatal day 34-45; "social experience," SE, subjects) or (b) underwent the same protocol with a familiar cagemate during mid-adolescence ("control experience," CE, subjects), or (c) were left undisturbed in the home cage (non-handled "control," C, subjects).

Human mate-choice copying is domain-general social learning.

Women appear to copy other women's preferences for men's faces. This 'mate-choice copying' is often taken as evidence of psychological adaptations for processing social information related to mate choice, for which facial information is assumed to be particularly salient. No experiment, however, has directly investigated whether women preferentially copy each other's face preferences more than other preferences.

Sex differences in the use of social information emerge under conditions of risk.

Social learning provides an effective route to gaining up-to-date information, particularly when information is costly to obtain asocially. Theoretical work predicts that the willingness to switch between using asocial and social sources of information will vary between individuals according to their risk tolerance. We tested the prediction that, where there are sex differences in risk tolerance, altering the variance of the payoffs of using asocial and social information differentially influences the probability of social information use by sex.

Sex differences in confidence influence patterns of conformity.

Lack of confidence in one's own ability can increase the likelihood of relying on social information. Sex differences in confidence have been extensively investigated in cognitive tasks, but implications for conformity have not been directly tested. Here, we tested the hypothesis that, in a task that shows sex differences in confidence, an indirect effect of sex on social information use will also be evident.

Sex differences in performance on a cognitive bias task in Norway rats.

Cognitive biases, which are defined as distortions in cognitive processes that are influenced by a background emotional state, can provide information about an individual's affective state. For instance, negative cognitive biases, where individuals assess ambiguous situations as unrewarding, are commonly found in humans suffering from anxiety disorders. Cognitive biases are also increasingly used as indicators of affective state in animals.

Ultrasonic vocalizations of female Norway rats (Rattus norvegicus) in response to social partners.

In many species of animals, male vocalizations function to attract mating partners and coordinate sexual interactions. Whereas male vocalizations have been well studied in several species, the function of female vocalizations in mating contexts is not fully understood. In Norway rats (Rattus norvegicus), both males and females produce ultrasonic vocalizations (USVs) during sexual encounters with opposite sex partners.

Peri-pubertal exposure to testicular hormones organizes response to novel environments and social behaviour in adult male rats.

Previous research has shown that exposure to testicular hormones during the peri-pubertal period of life has long-term, organizational effects on adult sexual behaviour and underlying neural mechanisms in laboratory rodents. However, the organizational effects of peri-pubertal testicular hormones on other aspects of behaviour and brain function are less well understood. Here, we investigated the effects of manipulating peri-pubertal testicular hormone exposure on later behavioural responses to novel environments and on hormone receptors in various brain regions that are involved in response to novelty.

Sex differences in interpretation bias in adolescents.

Interpretation biases, in which ambiguous information is interpreted negatively, have been hypothesized to place adolescent females at greater risk of developing anxiety and mood disorders than same-aged males. We tested the hypothesis that adolescent girls interpret ambiguous scenarios more negatively, and/or less positively, than same-aged males using the Adolescent Interpretation and Belief Questionnaire (N = 67, 11-15 years old). We also tested whether adolescent girls and boys differed in judging positive or negative interpretations to be more believable and whether the scenario content (social vs.

Sex differences in sensation-seeking: a meta-analysis.

Men score higher than women on measures of sensation-seeking, defined as a willingness to engage in novel or intense activities. This sex difference has been explained in terms of evolved psychological mechanisms or culturally transmitted social norms. We investigated whether sex differences in sensation-seeking have changed over recent years by conducting a meta-analysis of studies using Zuckerman's Sensation Seeking Scale, version V (SSS-V).

Effects of suppressing gonadal hormones on response to novel objects in adolescent rats.

Human adolescents exhibit higher levels of novelty-seeking behaviour than younger or older individuals, and novelty-seeking is higher in males than females from adolescence onwards. Gonadal hormones, such as testosterone and estradiol, have been suggested to underlie age and sex difference in response to novelty; however, empirical evidence in support of this hypothesis is limited. Here, we investigated whether suppressing gonadal hormone levels during adolescence affects response to novelty in laboratory rats.

Darwin in mind: new opportunities for evolutionary psychology.

Evolutionary Psychology (EP) views the human mind as organized into many modules, each underpinned by psychological adaptations designed to solve problems faced by our Pleistocene ancestors. We argue that the key tenets of the established EP paradigm require modification in the light of recent findings from a number of disciplines, including human genetics, evolutionary biology, cognitive neuroscience, developmental psychology, and paleoecology. For instance, many human genes have been subject to recent selective sweeps; humans play an active, constructive role in co-directing their own development and evolution; and experimental evidence often favours a general process, rather than a modular account, of cognition.

Ontogeny of sex differences in response to novel objects from adolescence to adulthood in lister-hooded rats.

In humans, novelty-seeking behavior peaks in adolescence and is higher in males than females. Relatively, little information is available regarding age and sex differences in response to novelty in rodents. In this study, male and female Lister-hooded rats were tested at early adolescence (postnatal day, pnd, 28), mid-adolescence (pnd 40), or early adulthood (pnd 80) in a novel object recognition task (n = 12 males/females per age group).

Evolutionary accounts of human behavioural diversity.

Human beings persist in an extraordinary range of ecological settings, in the process exhibiting enormous behavioural diversity, both within and between populations. People vary in their social, mating and parental behaviour and have diverse and elaborate beliefs, traditions, norms and institutions. The aim of this theme issue is to ask whether, and how, evolutionary theory can help us to understand this diversity.

The ontogeny of anxiety-like behavior in rats from adolescence to adulthood.

In human beings, susceptibility to anxiety disorders can be relatively high during adolescence. Understanding the ontogeny of anxiety-like behavior in laboratory rodents has implications for developing anxiolytic drugs that are suitable for this age group. Given the dearth of information about adolescent rodents, this study examined the response of both male and female adolescent, late adolescent, young adult, and older adult rats to three tests of anxiety-like behavior: the emergence test (ET), open field (OF), and elevated plus-maze (EPM).

The ontogeny of exploratory behavior in male and female adolescent rats (Rattus norvegicus).

During adolescence, rats gain independence from their mothers and disperse from the natal burrow, with males typically dispersing further than females. We predicted that, if dispersal patterns are associated with responsiveness to novelty, exploratory behavior in novel environments would increase across adolescence, and males would explore more than females. Alternatively, females might explore more than males, if females are more motivated than males to learn about the immediate environment or if females have poorer spatial abilities than males.

Bateman's principles and human sex roles.

In 1948, Angus J. Bateman reported a stronger relationship between mating and reproductive success in male fruit flies compared with females, and concluded that selection should universally favour 'an undiscriminating eagerness in the males and a discriminating passivity in the females' to obtain mates. The conventional view of promiscuous, undiscriminating males and coy, choosy females has also been applied to our own species.

Lessons from animal teaching.

Many species are known to acquire valuable life skills and information from others, but until recently it was widely believed that animals did not actively facilitate learning in others. Teaching was regarded as a uniquely human faculty. However, recent studies suggest that teaching might be more common in animals than previously thought.

Local resource competition and local resource enhancement shape primate birth sex ratios.

Sex ratio theory provides a powerful source of testable predictions about sex allocation strategies. Although studies of invertebrates generally support predictions derived from the sex ratio theory, evidence for adaptive sex ratio biasing in vertebrates remains contentious. This may be due to the fact that most studies of vertebrates have focused on facultative adjustment in relation to maternal condition, rather than processes that might produce uniform sex biases across individuals.

The exploratory behaviour of rats in the hole-board apparatus: is head-dipping a valid measure of neophilia?

The exploratory behaviour of laboratory rodents is of interest within a number of areas of behavioural pharmacology. However, how best to measure exploratory behaviour in rodents remains a contentious issue. Many unconditioned tests, such as the open field, potentially confound general locomotor activity with exploration.

Suppression of prolactin does not reduce infant care by parentally experienced male common marmosets (Callithrix jacchus).

High levels of prolactin have been found to correlate with the expression of paternal care in a variety of taxa. However, in mammals, there is little experimental evidence that prolactin is causally involved in the stimulation or maintenance of paternal care. Here, we suppressed prolactin production in paternally experienced common marmoset fathers in their family groups during the first 2 weeks after their infants were born.

Sexual selection: copycat mating in birds.

Female zebra finches may be influenced by the choices of other females when selecting mates, challenging the view that mate-choice copying should not occur in species with biparental care.

Maternal rank and local resource competition do not predict birth sex ratios in wild baboons.

We test two models of adaptive adjustment of birth sex ratios that are expected to apply to Cercopithecine primate species. It has been predicted that when maternal investment differentially influences the reproductive success of male and female offspring, females in good condition will bias investment in favour of the sex that gains the greatest fitness returns from additional investment. This hypothesis was subsequently amended to take into account the effects of local resource competition on maternal investment strategies of primate females.

Adult-infant food transfer in common marmosets: an experimental study.

Infant marmosets and tamarins obtain solid food items from adults during and after the time of weaning. In addition to providing nutrients, food transfers may provide infants with the opportunity to learn about diet. The aim of this study was to investigate patterns of begging and food transfer in captive groups of common marmosets during tests with 1) palatable novel food, 2) unpalatable novel food, and 3) familiar food.