Opposite-sex Stranger Research Articles

Empathic stress is decreased by prior stressor experience and increased in a position of power

The observation of a stressed individual can trigger a stress response in a passive observer. Little is known about the mechanisms of this so-termed empathic stress, including the observer's empathic involvement with the stressful situation. In 108 opposite-sex stranger dyads, we expected to increase the observer's empathic involvement with a stressed target performing a standardized laboratory stressor (Trier Social Stress Test, TSST; Kirschbaum et al., 1993) by exposing observers themselves to the TSST one week earlier. Conversely, we intended to decrease empathic involvement by granting observers a powerful position over the targets (by asking them to evaluate the targets' TSST performance and allegedly decide on their financial compensation). A control group without any manipulation was also included. In the preregistered data analysis, two types of empathic stress were investigated: vicarious stress, which evolves irrespective of the target's stress response, and stress resonance, which is proportional to the target's stress response. Irrespective of manipulation, observers exhibited vicarious stress in subjective and high-frequency heart rate variability (HF-HRV), and synchronized with the targets' stress reactivity in cortisol release. Prior TSST experience unexpectedly decreased observers' self-reported empathy and vicarious cortisol stress reactivity. The power manipulation, conversely, led to stronger observer vicarious stress in overall heart rate and HF-HRV reactivity. Based on Wondra and Ellsworth's (2015) appraisal theory, we propose that, due to their prior stressor exposure, observers habituated to said stressor, and consequently changed their evaluation of the target's stressful situation. In contrast, observers in the powerful position may have felt responsible for the targets, triggering a stronger vicarious stressful experience.

Effects of pairing on color change and central gene expression in lined seahorses.

Social monogamy is a reproductive strategy characterized by pair living and defense of a common territory. Pair bonding, sometimes displayed by monogamous species, is an affective construct that includes preference for a specific partner, distress upon separation, and the ability of the partner to buffer against stress. Many seahorse species show a monogamous social structure in the wild, but their pair bond has not been well studied. We examined the gene expression of lined seahorses (Hippocampus erectus) during and after the process of pairing in the laboratory as well as color change (luminance), a potential form of social communication and behavioral synchrony between pair mates. When a seahorse of either sex was interacting with its pair mate, their changes in luminance ("brightness") were correlated and larger than when interacting with an opposite-sex stranger. At the conclusion of testing, subjects were euthanized, RNA was extracted from whole brains and analyzed via RNA sequencing. Changes in gene expression in paired males versus those that were unpaired included processes governing metabolic activity, hormones and cilia. Perhaps most interesting is the overlap in gene expression change induced by pairing in both male seahorses and male prairie voles, including components of hormone systems regulating reproduction. Because of our limited sample size, we consider our results and interpretations to be preliminary, and prompts for further exploration. Future studies will expand upon these findings and investigate the neuroendocrine and genetic basis of these behaviors.

The Importance of Intact Senses in Mating and Social Assessments Made by Deaf Individuals

Social perception is a multimodal process involving vision and audition as central input sources for human social cognitive processes. However, it remains unclear how profoundly deaf people assess others in the context of mating and social interaction. The current study explored the relative importance of different sensory modalities (vision, smell, and touch) in assessments of opposite- and same-sex strangers. We focused on potential sensory compensation processes in mate selection (i.e., increased importance of the intact senses in forming impressions of an opposite-sex stranger as a potential partner). A total of 74 deaf individuals and 100 normally hearing controls were included in the study sample. We found diminished importance of vision and smell in deaf participants compared with controls for opposite- and same-sex strangers, and increased importance of touch for the assessment of same-sex strangers. The results suggested that deaf people rely less on visual and olfactory cues in mating and social assessments, highlighting a possible role of sign language in shaping interpersonal tactile experience in non-romantic relationships.

A randomized placebo-controlled intranasal oxytocin study on first impressions and reactions to social rejection

Oxytocin is central to pair-bonding in non-human animals. We assessed effects of intranasal oxytocin on bond formation between two opposite-sex strangers. In a double-blind placebo-controlled design, 50 pairs of one man and one woman received oxytocin or placebo spray intranasally. After treatment, they played a social interaction game, followed by tasks designed to measure first impressions of the opposite-sex co-participant, and a virtual ball-tossing game (cyberball), designed to measure reactions to rejection by the co-participant. We found no evidence that intranasal oxytocin can improve first impressions of an opposite-sex stranger, and some Bayesian support against this hypothesis. For rejection sensitivity, we observed a sex-and-context-dependent drug effect on post-ostracism mood ratings, consistent with recent studies indicating that interindividual variation and social context can interact with intranasal oxytocin effects. Further research is needed to determine the generalisability of these findings, i.e. if oxytocin can improve first impressions in humans under different conditions.

Effect of periodic social interaction and odour presentation of same and opposite-sex conspecifics on free-running mice

ABSTRACT Social interaction, a non-photic cue, plays a role in the synchronization of circadian rhythm under constant environmental conditions. However, little is known about the effect of sex-specific interaction and sex-specific odor on the free-running circadian clock of mice. Hence, in the present study, we investigated the effect of social interaction and odor presentation of same and opposite-sex conspecifics on the free-running rhythm of mice. In this investigation, stranger and dummy mice (saturated with either male- or female-associated odor) were separately exposed to the same and opposite-sex conspecifics of male and female runners and receivers, respectively for 30 min at CT15 for 10–12 d. The results showed that the daily exposure of runners with same and opposite-sex strangers entrained the free-running locomotor activity rhythm in a gender-specific manner. However, daily exposure of same and opposite-sex conspecific odors masked the circadian rhythm of receiver animals by increasing the activity. Further, social interaction and odor presentation caused lengthened and shortened period length, respectively. These results suggest that periodic social interactions can produce entrainment and conspecific odor can produce only masking on free-running circadian locomotor activity rhythm in mice.

Relationship tenure differentially influences pair-bond behavior in male and female socially monogamous titi monkeys (Callicebus cupreus).

Pair-bonded primates have uniquely enduring relationships and partners engage in a suite of behaviors to maintain these close bonds. In titi monkeys, pair bond formation has been extensively studied, but changes across relationship tenure remain unstudied. We evaluated differences in behavioral indicators of pair bonding in newly formed (~6 months paired, n = 9) compared to well-established pairs (average 3 years paired, n = 8) of titi monkeys (Callicebus cupreus) as well as sex differences within the pairs. We hypothesized that overall males would contribute more to maintenance than females, but that the pattern of maintenance behaviors would differ between newly formed and well-established pairs. Each titi monkey (N = 34) participated in a partner preference test (PPT), where the subject was placed in a middle test cage with grated windows separating the subject from the partner on one side and an opposite-sex stranger on the other side. During this 150-min behavioral test, we quantified four key behaviors: time in proximity to the partner or stranger as well as aggressive displays toward the partner or stranger. Overall, we found different behavioral profiles representing newly formed and well-established pair-bond relationships in titi monkeys and male-biased relationship maintenance. Males spent ∼40% of their time in the PPT maintaining proximity to the female partner, regardless of relationship tenure. Males from well-established bonds spent less time (14%) near the female stranger compared to males from newly formed bonds (21%) at the trend level. In contrast, females from well-established bonds spent less (23%) time near the male partner in the PPT compared to females from newly formed bonds (47%). Aggressive displays were more frequent in newly formed bonds compared to well-established bonds, especially for females. Scan sampling for homecage affiliation showed that newly formed pairs were more likely to be found tail twining than well-established pairs.

Making the right first impression: Sexual priming encourages attitude change and self-presentation lies during encounters with potential partners

Recent studies have shown that activation of the sexual system encourages enactment of relationship-initiating behaviors (Birnbaum et al., 2017). In four studies, we expand on this work to explore whether people are more inclined to lie to impress a potential partner following sexual priming. In all studies, participants were exposed to sexual stimuli (versus non-sexual stimuli) and then interacted with an opposite-sex stranger. In Study 1, unacquainted participants resolved a dilemma while each represented opposing positions. In Study 2, participants rated their preferences, and after viewing a confederate's preferences, re-rated them in a profile shown to the confederate. In Studies 3 and 4, participants reported their number of lifetime sexual partners in anonymous questionnaires and during a chat (Study 3) or while completing an online profile (Study 4). Results indicated that following sexual priming, participants were more likely to conform to the stranger's views (Studies 1 and 2) and reported fewer sexual partners during actual and potential online interactions than in the questionnaires (Study 3). Although the results of Study 4 did not replicate the findings of Study 3, they were directionally consistent with them. Overall, the findings suggest that sexual priming motivates impression management even when it involves lying.

Evaluating the stability of individual variation in social and nonsocial behavioural types using prairie voles (Microtus ochrogaster)

Prairie voles (Microtus ochrogaster) exhibit remarkable individual variation in social behaviour, suggesting differences in behavioural types. To date, however, there has been little assessment of whether these behavioural types are stable across test sessions, nor to what extent internal states and external contexts (domains) drive individual differences. Here we examined the individual consistency of social (huddling) and non-social (distance moved) behaviour across repeated, long-duration tests, in same-sex cagemate (SS-CM), same-sex stranger (SS-S), opposite-sex stranger (OS-S), and standard partner preference test (PPT) contexts. The SS-CM and SS-S tests were repeated multiple times (SS-CM 1–2; SS-S 1–5) to assess state-dependent variation. A second cohort was used to determine the replicability of findings. Overall, there was a general lack of stability in huddling behavior. It was inconsistent across repeated sessions of the same test type and between types of tests, suggesting a strong contribution of state-dependent variation. Non-social behaviour was more consistent and appeared more domain-dependent and less state-dependent than huddling. Translational and comparative studies of individual variation would likely benefit from testing across multiple contexts and employing repetitive testing paradigms to account for state-dependent variation.

Oxytocin structure and function in New World monkeys: from pharmacology to behavior.

Oxytocin (OT) is a hypothalamic nonapeptide that mediates a host of physiological and behavioral processes including reproductive physiology and social attachments. While the OT sequence structure is highly conserved among mammals, New World monkeys (NWMs) represent an unusual "hot spot" in OT structure variability among mammals. At least 6 distinct OT ligand variants among NWMs exist, yet it is currently unclear whether these evolved structural changes result in meaningful functional consequences. NWMs offer a new area to explore how these modifications to OT and its canonical G-protein coupled OT receptor (OTR) may mediate specific cellular, physiological and behavioral outcomes. In this review, we highlight relationships between OT ligand and OTR structural variability, specifically examining coevolution between OT ligands, OTRs, and physiological and behavioral phenotypes across NWMs. We consider whether these evolved modifications to the OT structure alter pharmacological profiles at human and marmoset OTRs, including changes to receptor binding, intracellular signaling and receptor internalization. Finally, we evaluate whether exogenous manipulation using OT variants in marmoset monkeys differentially enhance or impair behavioral processes involved in social relationships between pairmates, opposite-sex strangers, and parents and their offspring. Overall, it appears that changes to OT ligands in NWMs result in important changes ranging from cellular signaling to broad measures of social behavior.

Interpersonal Touch Buffers Pain Sensitivity in Romantic Relationships but Heightens Sensitivity between Strangers and Friends

A variety of evidence suggests that interpersonal behaviors such as touch can have pain-alleviating effects on recipients. Less well understood is how touch affects sensitivity to pain in the first place, and whether its effects depend on the nature of the relationship in which it occurs. In the present experiment, 55 adults who had not been diagnosed with a pain disorder were exposed to a cold pressor pain induction with an opposite-sex stranger, platonic friend, or romantic partner who either touched their shoulders, was present in the room without touching them, or was absent during the cold pressor. The outcome variable was the self-reported level of pain induced by the stimulus at the moment when the stimulus became painful (i.e., pain sensitivity). Compared to presence or absence, touch dampened pain sensitivity for romantic partners, allowing them to tolerate more intensity before the stimulus became painful. Touch had the opposite effect for friends and strangers, heightening their sensitivity to pain.

Dopamine Modulation of Reunion Behavior in Short and Long Term Marmoset Pairs

One major neurobiological substrate regulating social processes is dopamine (DA). DA is implicated in social behavior in species as diverse as fish and birds, and has an established role in regulating relationships between mates in socially monogamous rodents. Marmoset monkeys display traits associated with social monogamy including high rates of affiliation, biparental care, distress upon separation, and aggression toward strangers; several of these behavioral patterns change throughout the development of relationships. This temporal change may represent changing demands, as pairs are likely to jointly face new experiences (e.g., parenthood) throughout pairing. We investigated the role of DA and pairing length on social behavior during reunion after separation from the partner. Marmosets were removed from their home environment and treated with agonists and antagonists for the D1 and D2 receptor subtypes. They were exposed to a novel environment containing an opposite-sex stranger and the pair mate, and then reunited with their mate in the home enclosure. Marmosets in long term pairs exhibited higher levels of food sharing during reunion than marmosets in short term pairs, with females in long term pairs sharing food more than males; no sex difference were observed in short term pairs. Subjects in short term pairs spent more time grooming their mate than receiving grooming during reunion, while marmosets in long term pairs displayed similar amounts of both initiated and received grooming. DA treatment altered pair-level behavior. When females received either a D2 agonist or antagonist, short term pairs spent less time in proximity, compared to when males received the same treatments. In long term pairs, treatment of females with either a D1 agonist or antagonist resulted in pairs spending less time in social proximity than when males were treated. These findings suggest that the function of the DA system in mate behavior may be similar between rodents and primates, with the D1 system modulating the expression of behavior in long term pairs and the D2 system regulating behavior in short term pairs. Furthermore, these results supplement a large body of work suggestive of deep evolutionary roots of the DA system in regulating social behavior.

Oxytocin regulates reunion affiliation with a pairmate following social separation in marmosets.

While separation from significant social partners produces a host of neurobiological and behavioral perturbations, including behavioral distress and increased glucocorticoid production, positive social interactions upon reunion are critical for the reestablishment of normative relationship dynamics and the attenuation of the biobehavioral stress response. The hormone oxytocin has critical and pervasive roles in reproductive and behavioral processes across the lifespan, and plays a particularly prominent role in social bonding. In this study, we examined the extent that oxytocin modulates interactions with a pairmate following separation challenges that varied in both social context (isolation; separation) and duration (long; short), in marmosets. We demonstrated that the impact of pharmacological manipulations of the oxytocin system on the expression of affiliation upon reunion depended on both the context and duration of the separation challenge. Specifically, marmosets treated with an oxytocin antagonist spent less time in proximity with their pairmate upon reunion following a long-separation challenge. During the short-separation challenge, marmosets engaged in more social gaze when separated with an opposite-sex stranger, but not when separated with their mate. Furthermore, marmosets that received the most social gaze from opposite-sex strangers spent the most time in proximity with their long-term mate upon reunion. We also showed that marmosets treated with an OT agonist received increased levels of gaze from opposite-sex strangers, but not from their mate. Overall, these results suggest that marmosets are sensitive to the nature of the social interactions during separation, and subsequently alter their expression of affiliation upon reunion with their long-term mate. These findings further implicate oxytocin as a bond-enhancing molecule that regulates the reestablishment of normative levels of affiliation with a mate following separation, and add to the emerging literature that suggests the OT system underlies critical behavioral processes that contribute to the preservation of long-lasting social bonds.

A Compensatory Effect on Mate Selection? Importance of Auditory, Olfactory, and Tactile Cues in Partner Choice among Blind and Sighted Individuals

Human attractiveness is a potent social variable, and people assess their potential partners based on input from a range of sensory modalities. Among all sensory cues, visual signals are typically considered to be the most important and most salient source of information. However, it remains unclear how people without sight assess others. In the current study, we explored the relative importance of sensory modalities other than vision (smell, touch, and audition) in the assessment of same- and opposite-sex strangers. We specifically focused on possible sensory compensation in mate selection, defined as enhanced importance of modalities other than vision among blind individuals in their choice of potential partners. Data were obtained from a total of 119 participants, of whom 78 were blind people aged between 16 and 65 years (M = 42.4, SD = 12.6; 38 females) and a control sample of 41 sighted people aged between 20 and 64. As hypothesized, we observed a compensatory effect of blindness on auditory perception. Our data indicate that visual impairment increases the importance of audition in different types of social assessments for both sexes and in mate choice for blind men.

Pre- and Postinteraction Physical Attractiveness Ratings and Experience-Based Impressions

This study examines the perceptions of an interaction partner’s physical attractiveness and traits in relation to whether and how partners were evaluated prior to interacting. Sixty-five pairs of heterosexual strangers were randomly assigned to one of three conditions (i.e., prerate photos of opposite-sex strangers including conversation partner, prerate photos excluding partner, no prerate photos). Participants then had a 10-minute interaction, reported impressions of partner, and rated photos again including the partner. Compared to no preinteraction rating, rating conversation partners’ attractiveness reduced impressions of partners’ social attractiveness, fun/funniness, and charisma. Partner impressions were more strongly associated with postinteraction attractiveness ratings than preinteraction ratings. Impressions of social attractiveness and fun/funniness moderated attractiveness rating change, wherein less attractive partners showed more positive change than attractive partners.

Sex Unleashes Your Tongue: Sexual Priming Motivates Self-Disclosure to a New Acquaintance and Interest in Future Interactions.

Research has demonstrated the contribution of sexual activity to the quality of ongoing relationships. Nevertheless, less attention has been given to how activation of the sexual system affects relationship-initiation processes. Three studies used complementary methodologies to examine the effect of sexual priming on self-disclosure, a relationship-promoting behavior. In Study 1, participants were subliminally exposed to sexual stimuli (vs. neutral stimuli), and then disclosed over Instant Messenger a personal event to an opposite-sex stranger. Results showed that merely thinking about sex, even without being aware of it, encouraged self-disclosure. Study 2 replicated these findings in relatively naturalistic conditions (live face-to-face interactions following supraliminal video priming). Study 3 extended these findings, indicating that sexual priming facilitated self-disclosure, which, in turn, increased interest in future interactions with the stranger. Together, these findings suggest that activation of the sexual system encourages the use of strategies that allow people to become closer to potential partners.

Inequity aversion strategies between marmosets are influenced by partner familiarity and sex but not by oxytocin

Cooperation among individuals depends, in large part, on a sense of fairness. Many cooperating non-human primates (NHPs) show inequity aversion, (i.e., negative responses to unequal outcomes), and these responses toward inequity likely evolved as a means to preserve the advantages of cooperative relationships. However, marmosets (Callithrix spp.) tend to show little or no inequity aversion, despite the high occurrence of prosociality and cooperative-breeding in callitrichid monkeys. Oxytocin [OXT] has been implicated in a wide variety of social processes, but little is known about whether OXT modulates inequity aversion toward others. We used a tray pulling task to evaluate whether marmosets would donate superior rewards to their long-term pairmate or an opposite-sex stranger following OXT, OXT antagonist, and saline treatments. We found that marmosets show inequity aversion, and this inequity aversion is socially- and sex-specific. Male marmosets show inequity aversion toward their pairmates but not strangers, and female marmosets do not show inequity aversion. OXT treatments did not significantly influence inequity aversion in marmosets. While OXT may modulate prosocial preferences, the motivations underlying cooperative relationships, such as inequity aversion, are multifaceted. More research is needed to evaluate the evolutionary origins, biological processes, and social contexts that influence complex phenotypes like inequity aversion. Inequity aversion can differ within species in important and distinct ways including between individuals who do and do not share a cooperative relationship. Overall, these findings support the view that inequity aversion is an important behavioural strategy for the maintenance of cooperative relationships.

Sexual Selection and Humor in Courtship : A Case for Warmth and Extroversion.

This investigation examines a sexual selection-based argument regarding humor's role in courtship (i.e., humor production signals intelligence/creativity). Lens model (n =100) analyses suggest that humor production on Facebook profiles were self-reported and perceived to be associated with extroversion, not intelligence. Study 2 (n = 289) found that extroversion was associated humor production, but high school and college grade point average and American College Test (ACT) scores were not. In Study 3, pairs of opposite-sex strangers (n = 102) interacted for 10-12 min. Males' humor production and females' responsive laughter were both associated with females' dating interest. Both partners' dating interest was associated with simultaneous laughter. Without support for the sexual selection argument, three alternative explanations of humor's role in courtship are discussed.

Development of a partner preference test that differentiates between established pair bonds and other relationships in socially monogamous titi monkeys (Callicebus cupreus).

Partner preference, or the selective social preference for a pair mate, is a key behavioral indicator of social monogamy. Standardized partner preference testing has been used extensively in rodents but a single test has not been standardized for primates. The goal of this study was to develop a partner preference test with socially monogamous titi monkeys (Callicebus cupreus) adapted from the widely used rodent test. In Experiment 1, we evaluated the test with pairs of titi monkeys (N = 12) in a three-chambered apparatus for 3 hr. The subject was placed in the middle chamber, with grated windows separating it from its partner on one side and an opposite sex stranger on the other side. Subjects spent a greater proportion of time in proximity to their partners' windows than the strangers', indicating a consistent preference for the partner over the stranger. Touching either window did not differ between partners and strangers, suggesting it was not a reliable measure of partner preference. Subjects chose their partner more than the stranger during catch and release sessions at the end of the test. In Experiment 2, we compared responses of females with current partners (N = 12) in the preference test with other relationship types representing former attachment bonds (N = 13) and no attachment bond (N = 8). Only females from established pair bonds spent significantly more time near their partner's window compared to the stranger's indicating that this measure of preference was unique to current partners. Other measures of preference did not differentiate behavior toward a current partner and other relationship types. This test reproduces behavioral patterns found in previous studies in titi monkeys highlighting the accuracy of this new partner preference test. This test can be used as a standardized measure of partner preference in titi monkeys to quantitatively study pair bonding and evaluate factors influencing partner preference.

Do marmosets care to share? Oxytocin treatment reduces prosocial behavior toward strangers

Cooperatively-breeding and socially-monogamous primates, like marmosets and humans, exhibit high levels of social tolerance and prosociality toward others. Oxytocin (OXT) generally facilitates prosocial behavior, but there is growing recognition that OXT modulation of prosocial behavior is shaped by the context of social interactions and by other motivational states such as arousal or anxiety. To determine whether prosociality varies based on social context, we evaluated whether marmoset donors (Callithrix penicillata) preferentially rewarded pairmates versus opposite-sex strangers in a prosocial food-sharing task. To examine potential links among OXT, stress systems, and prosociality, we evaluated whether pretrial cortisol levels in marmosets altered the impact of OXT on prosocial responses. Marmosets exhibited spontaneous prosociality toward others, but they did so preferentially toward strangers compared to their pairmates. When donor marmosets were treated with marmoset-specific Pro8-OXT, they exhibited reduced prosociality toward strangers compared to marmosets treated with saline or consensus-mammalian Leu8-OXT. When pretrial cortisol levels were lower, marmosets exhibited higher prosociality toward strangers. These findings demonstrate that while marmosets show spontaneous prosocial responses toward others, they do so preferentially toward opposite-sex strangers. Cooperative breeding may be associated with the expression of prosociality, but the existence of a pair-bond between marmoset partners appears to be neither necessary nor sufficient for the expression of spontaneous prosocial responses. Furthermore, high prosociality toward strangers is significantly reduced in marmosets treated with Pro8-OXT, suggesting that OXT does not universally enhance prosociality, but, rather OXT modulation of prosocial behavior varies depending on social context.

Why do men prefer nice women? Gender typicality mediates the effect of responsiveness on perceived attractiveness in initial acquaintanceships.

Responsiveness may signal to a potential partner that one is concerned with her or his welfare, and may therefore increase sexual interest in this person. Research shows, however, that this proposition holds true for men, but not for women. In three studies, one observational and two experimental, we explored a potential mechanism that explains why men and women diverge in their sexual reactions to a responsive opposite-sex stranger. Studies 1 and 2 showed that men, but not women, perceived a responsive stranger as more gender typical (masculine/feminine) and, in turn, as more attractive. Study 3 revealed that responsiveness increased men's perception of partner's femininity. This, in turn, was associated with higher sexual arousal, which was, in turn, linked to greater partner attractiveness and greater desire for a long-term relationship. These findings suggest that whether responsiveness affects perceptions of partner attractiveness varies in individuals, depending on the contextually based meaning of responsiveness.