Effects of the menstrual cycle on looking preferences for faces in female rhesus monkeys

Fluctuations of ovarian hormones across the menstrual cycle influence a variety of social and cognitive behaviors in primates. For example, female rhesus monkeys exhibit heightened interest for males and increased agonistic interactions with other females during periods of high estrogen levels. In the present study, we hypothesized that females’ preference for males during periods of high estrogen levels is also expressed at the level of face perception. We tested four intact females on two face-tasks involving neutral portraits of male and female rhesus monkeys, chimpanzees and humans. In the visual preference task (VP), monkeys had to touch a button to view a face image. The image remained on the screen as long as the button was touched, and the duration of pressing was taken as an index of the monkey's looking time for the face stimulus. In the Face-Delayed Recognition Span Test (Face-DRST), monkeys were rewarded for touching the new face in an increasing number of serially presented faces. Monkeys were tested 5 days a week across one menstrual cycle. Blood was collected every other day for analysis of estradiol and progesterone. Two of the four females were cycling at the time of testing. We did not find an influence of the cycle on Face-DRST, likely due to a floor effect. In the VP however, the two cycling individuals looked longer at conspecific male faces than female faces during the peri-ovulatory period of the cycle. Such effects were absent for human and chimpanzee faces and for the two noncycling subjects. These data suggest that ovarian hormones may influence females’ preferences for specific faces, with heightened preference for male faces during the peri-ovulatory period of the cycle. Heightened interest for stimuli of significant reproductive relevance during periods of high conception risk may help guide social and sexual behavior in the rhesus monkey.     

Positional inference in rhesus macaques

Animal Cognition - Understanding how organisms make transitive inferences is critical to understanding their general ability to learn serial relationships. In this context, transitive inference...     

Explaining sex differences in infants' preferences for groups

Social organization of a species influences myriad facets of individuals’ behavior. Much research indicates that human social organization consists of males in large groups and females in smaller groups or interacting with individuals. This study analyzed the initial factors that produce greater preferences for groups by human male versus female infants. To this end, using a looking preference paradigm, fifty-nine 6–8-month-old infants viewed individual versus group images of actual children. On the basis of several controls, results demonstrated that male more than female infants are attracted to the complex level of stimulation provided by groups. Discussion centers on further identifying male versus female patterns of group interaction from a perceptual and cognitive standpoint.     

Intersexual aggression and male sexual activity in captive rhesus macaques

Rape has been posited to be an outgrowth of male reproductive strategies. Forced copulations may have evolved as a consequence of the low parental investment made by males in producing and raising offspring. We designed a laboratory experiment which paired rhesus macaque males with females in order to assess the influence of intersexual aggression on male sexual activity. Younger and older adult males had comparable levels of sexual behavior, but younger males were more aggressive towards females than were older males. In addition, females threatened younger males more than older males. Male attacks on females did not result in sexual intercourse. On the contrary, a negative correlation existed between male aggression towards females and male success at achieving intromissions. Female aggression towards males appeared to be an effective tactic which reduced the chances of sexual intercourse. We conclude that intersexual aggression acts either as a mechanism of dominance assertion or as a means to increase spatial distance between individuals. These data do not support the idea that rape in humans has an evolutionary foundation derived from male reproductive strategies.     

Men's strategic preferences for femininity in female faces

Several evolutionarily relevant sources of individual differences in face preference have been documented for women. Here, we examine three such sources of individual variation in men's preference for female facial femininity: term of relationship, partnership status and self‐perceived attractiveness. We show that men prefer more feminine female faces when rating for a short‐term relationship and when they have a partner (Study 1). These variables were found to interact in a follow‐up study (Study 2). Men who thought themselves attractive also preferred more feminized female faces for short‐term relationships than men who thought themselves less attractive (Study 1 and Study 2). In women, similar findings for masculine preferences in male faces have been interpreted as adaptive. In men, such preferences potentially reflect that attractive males are able to compete for high‐quality female partners in short‐term contexts. When a man has secured a mate, the potential cost of being discovered may increase his choosiness regarding short‐term partners relative to unpartnered men, who can better increase their short‐term mating success by relaxing their standards. Such potentially strategic preferences imply that men also face trade‐offs when choosing relatively masculine or feminine faced partners. In line with a trade‐off, women with feminine faces were seen as more likely to be unfaithful and more likely to pursue short‐term relationships (Study 3), suggesting that risk of cuckoldry is one factor that may limit men's preferences for femininity in women and could additionally lead to preferences for femininity in short‐term mates.     

Visual orientation preferences in the rat

An experiment was performed which demonstrated a preference in hooded rats for vertical rather than horizontal striatums. It was demonstrated that experience in discriminating between horizontal and vertical striations facilitates subsequent discrimination between squares and circles, regardless of which type of striation was positive in initial training. This finding has implications for theories of shape recognition, which are discussed.     

Correlated male preferences for femininity in female faces and voices

Sexually dimorphic physical traits are important for mate choice and mate preference in many species, including humans. Several previous studies have observed that women's preferences for physical cues of male masculinity in different domains (e.g., visual and vocal) are correlated. These correlations demonstrate systematic, rather than arbitrary, variation in women's preferences for masculine men and are consistent with the proposal that sexually dimorphic cues in different domains reflect a common underlying aspect of male quality. Here we present evidence for a similar correlation between men's preferences for different cues of femininity in women; although men generally preferred feminized to masculinized versions of both women's faces and voices, the strength of men's preferences for feminized versions of female faces was positively and significantly correlated with the strength of their preferences for feminized versions of women's voices. In a second study, this correlation occurred when men judged women's attractiveness as long-term, but not short-term, mates, which is consistent with previous research. Collectively, these findings (1) present novel evidence for systematic variation in men's preferences for feminine women, (2) present converging evidence for concordant preferences for sexually dimorphic traits in different domains, and (3) complement findings of correlations between women's facial and vocal femininity.     

Hypoglycemia-induced suppression of luteinizing hormone (LH) secretion in intact female rhesus macaques: role of vasopressin and endogenous opioids

The first objective of this study was to determine whether insulin-induced hypoglycemia (IIH) inhibits LH secretion in unrestrained female macaques during the follicular phase of the menstrual cycle. There was a consistent inhibitory effect of hypoglycemia on LH secretion within 3 h in these females. This inhibition was likely an indirect effect since low glucose levels did not inhibit GnRH secretion from GT1-1 neurones in vitro. We next investigated whether administration of a vasopressin antagonist (AVPa) either alone, or with naloxone could reverse the IIH-induced inhibition of LH release. Females were studied in the follicular phase during 10 h periods with blood samples collected every 10 min. Experimental groups were IIH (n=6), IIH+AVPa (n=5) and IIH+AVPa+naloxone (n=4). The first 5 h of each study served as a control and hypoglycemia was then induced with insulin. The AVPa was given as a bolus (180 microg) just before the insulin and was followed by a continuous infusion (180 microg/h) for 5 h. Naloxone (5 mg/kg) was given with the AVPa and followed by a continuous infusion (5 mg/kg/h) for 5 h. In the IIH group, LH reached its lowest value 3-4 h after insulin. Neither AVPa nor AVPa+naloxone infusion reversed the inhibitory action of hypoglycemia on LH release. These data suggest that if there are inhibitory actions of vasopressin and endogenous opioids on GnRH release induced by hypoglycemia, they are not sufficient to explain the suppression of GnRH/LH release in intact female primates.     

Affiliative vocalizations in infant rhesus macaques (Macaca mulatta).

In Experiment 1, infant rhesus monkeys (Macaca mulatta) were separated and then reunited with mothers, united with a male, or placed in an empty cage. Infants girned more when with mothers or the male than when alone. Girns declined over time when infants were united with the male. Coo rates were high when the infant was alone or with the male. Shrieks, barks, and fear-related behavior were higher with the male. In Experiment 2 the vocalizations of infants were examined during separation when alone or when mothers or a male were in the same room. Infants cooed more when mothers or a male were present. Cooing increased over time, with a greater increase in the mothers' presence. Girns were given to both mothers and males, but more were given to mothers. Coos and girns are both affiliative vocalizations but are differentially modulated as infants cease cooing when they receive contact comfort.     

Seeing two faces together: preference formation in humans and rhesus macaques

Humans, great apes and old world monkeys show selective attention to faces depending on conspecificity, familiarity, and social status supporting the view that primates share similar face processing mechanisms. Although many studies have been done on face scanning strategy in monkeys and humans, the mechanisms influencing viewing preference have received little attention. To determine how face categories influence viewing preference in humans and rhesus macaques (Macaca mulatta), we performed two eye-tracking experiments using a visual preference task whereby pairs of faces from different species were presented simultaneously. The results indicated that viewing time was significantly influenced by the pairing of the face categories. Humans showed a strong bias towards an own-race face in an Asian–Caucasian condition. Rhesus macaques directed more attention towards non-human primate faces when they were paired with human faces, regardless of the species. When rhesus faces were paired with faces from Barbary macaques (Macaca sylvanus) or chimpanzees (Pan troglodytes), the novel species’ faces attracted more attention. These results indicate that monkeys’ viewing preferences, as assessed by a visual preference task, are modulated by several factors, species and dominance being the most influential.     

The evolution of intergroup bias: perceptions and attitudes in rhesus macaques

Social psychologists have learned a great deal about the nature of intergroup conflict and the attitudinal and cognitive processes that enable it. Less is known about where these processes come from in the first place. In particular, do our strategies for dealing with other groups emerge in the absence of human-specific experiences? One profitable way to answer this question has involved administering tests that are conceptual equivalents of those used with adult humans in other species, thereby exploring the continuity or discontinuity of psychological processes. We examined intergroup preferences in a nonhuman species, the rhesus macaque (Macaca mulatta). We found the first evidence that a nonhuman species automatically distinguishes the faces of members of its own social group from those in other groups and displays greater vigilance toward outgroup members (Experiments 1-3). In addition, we observed that macaques spontaneously associate novel objects with specific social groups and display greater vigilance to objects associated with outgroup members (Experiments 4-5). Finally, we developed a looking time procedure-the Looking Time Implicit Association Test, which resembles the Implicit Association Test (Greenwald & Banaji, 1995)-and we discovered that macaques, like humans, automatically evaluate ingroup members positively and outgroup members negatively (Experiments 6-7). These field studies represent the first controlled experiments to examine the presence of intergroup attitudes in a nonhuman species. As such, these studies suggest that the architecture of the mind that enables the formation of these biases may be rooted in phylogenetically ancient mechanisms.     

Retrospective and prospective metacognitive judgments in rhesus macaques (Macaca mulatta)

A growing body of research suggests that some non-human animals are capable of making accurate metacognitive judgments. In previous studies, non-human animals have made either retrospective or prospective judgments (about how they did on a test or how they will do on a test, respectively). These two types of judgments are dissociable in humans. The current study tested the abilities of two rhesus macaque monkeys to make both retrospective and prospective judgments about their performance on the same memory task. Both monkeys had been trained previously to make retrospective confidence judgments. Both monkeys successfully demonstrated transfer of retrospective metacognitive judgments to the new memory task. Furthermore, both monkeys transferred their retrospective judgments to the prospective task (one, immediately, and one, following the elimination of a response bias). This study is the first to demonstrate both retrospective and prospective monitoring abilities in the same monkeys and on the same task, suggesting a greater level of flexibility in animals’ metacognitive monitoring abilities than has been reported previously.     

Self-control in rhesus macaques (Macaca mulatta): controlling for differential stimulus exposure

Previous research on self-control using macaques (Macaca fascicularis) showed these animals have a strong bias for a delayed, larger reinforcer (Self-control) over an immediate, smaller reinforcer (Impulsive). Typical studies of self-control have used a discrete trials methodology with a secondary discriminative stimulus during the delay periods. This results in a greater exposure to the stimulus representing the self-controlled option and may account for some of the early exclusive preference for self-control observed. The present experiment examined self-control bias in three rhesus macaques (Macaca mulatta) while controlling for differential durations of stimulus exposure. Subjects were presented stimuli via a computer monitor and made choices by touching the stimulus at which point both stimuli were removed for the delay periods. All three subjects displayed a nearly exclusive bias for the delayed, larger reinforcer self-control). These results are consistent with previous studies, despite the variations in methodology and species.     

Parental preferences regarding sex education topics for sixth graders

The purpose of this study was to ascertain which sex education topics parents of preadolescents regarded as appropriate for their children. The sample was comprised of 146 respondents randomly selected from a class list of sixth graders in a suburban school district. A mailed, self-administered questionnaire listing 48 possible topics was used to elicit parental response. Pretesting found the questionnaire to be highly reliable (Cronbach's alpha = .95). Overall, parents strongly supported the inclusion of a broad range of sex education topics regardless of parental age, sex, marital status, income, education, or child's sex. Moreover, parents were largely in agreement with the inclusion of sensitive topics in addition to those which were more physiological or behavioral. Catholics more often than Protestants agreed with the inclusion of birth control, abortion, and sterilization even after controlling for income and education. Thus, the findings suggest that parents of sixth graders find a broad sex education program in the school appropriate. To this end, school officials and sex educators should not overlook the needs of preadolescents for sex education solely on the basis of perceived parental opposition.     

Sex differences in the preferences for specific female body shapes

The purpose of this study was to examine the somatic preferences of males and females for detailed anatomical drawings of female stimulus figures to examine their ability to predict the preferences for members of the opposite sex. The figures were systematically varied on three dimensions (bust, waist, and hips), with three sizes of each (small, medium, and large). The 12 figures were rated by 100 male and female subjects on a 7-point bipolar construct scale, ranging from extremely attractive to extremely unattractive. This was done both for the subjects' personal perceptions and for their predicted ratings of the opposite sex. Multivariate and univariate analyses yielded several sex, rating-perceptive (self vs. other), figure shape differences and interactions. Male subjects displayed a preference for large busts and hourglass shapes, which are accurately predicted by the females. Males predicted that females would rate slimmer figure highly, and females predicted that males would rate larger figures highly. The results are considered in light of related research in this area.     

A cage-based training,cognitive testing and enrichment system optimized for rhesus macaques in neuroscience research

In neurophysiological studies with awake non-human primates (NHP), it is typically necessary to train the animals over a prolonged period of time on a behavioral paradigm before the actual data collection takes place. Rhesus monkeys (Macaca mulatta) are the most widely used primate animal models in system neuroscience. Inspired by existing joystick- or touch-screen-based systems designed for a variety of monkey species, we built and successfully employed a stand-alone cage-based training and testing system for rhesus monkeys (eXperimental Behavioral Intrument, XBI). The XBI is mobile and easy to handle by both experts and non-experts; animals can work with only minimal physical restraints, yet the ergonomic design successfully encourages stereotypical postures with a consistent positioning of the head relative to the screen. The XBI allows computer-controlled training of the monkeys with a large variety of behavioral tasks and reward protocols typically used in systems and cognitive neuroscience research.     

Partner preferences across sexual orientations and biological sex

This study examined how partner preferences differ across interpersonal contexts (romantic attachment and relationship expectations) based on sexuality and biological sex. Participants completed measures of attachment and behavioral expectations for their romantic partners, cross‐sex friends, and same‐sex friends. The attachment anxiety results revealed an effect of sexuality: Single heterosexuals scored higher for their cross‐sex friends than same‐sex friends, single lesbian/gay individuals scored higher for same‐sex friends than cross‐sex friends, and bisexuals' attachment anxiety was equal regardless of friends' biological sex. The behavioral expectation results revealed an effect of biological sex indicating that, regardless of sexuality, women are preferred over men for emotional/social needs. Finally, an interaction revealed that lesbians have higher expectations for their girlfriends/wives than straight men have for theirs.