Fueled by desire: Sexual activation facilitates the enactment of relationship-initiating behaviors

Abstract

Sexual desire has long been theorized to serve a relationship-initiation function by bringing partners together. Four studies addressed this possibility, examining whether activation of the sexual system encouraged the enactment of nonsexual behaviors that signal warmth and contact readiness. In Study 1, participants mimed together with an opposite-sex confederate to prerecorded music. Participant’s desire for the confederate was associated with coded immediacy behaviors toward the confederate (e.g., proximity seeking, synchronization). Study 2 extended these findings, showing that participants, who slow danced with a confederate perceived to be more desirable, were more synchronized with the confederate. Synchronization, in turn, was associated with greater interest in future interactions with the confederate. Studies 3 and 4 established a causal connection between sexual activation and engagement in relationship-promoting behaviors (provision of responsiveness and help, respectively). These findings suggest that intense desire, which attracts new partners to each other, elicits behaviors that support the attachment-bonding process.

Keywords

Attraction dating relationship initiation responsiveness sexual desire sexuality synchrony

Evolutionary and attachment scholars have long theorized that sexual desire serves as a powerful motivational force that brings potential romantic partners together initially (Berscheid & Reis, 1998; Birnbaum & Gillath, 2006) and thereby helps to facilitate reproductive acts (Birnbaum, Mikulincer, Szepsenwol, Shaver, & Mizrahi, 2014). As such, sexual desire is not necessarily connected to attachment processes (Diamond, 2013). And yet, scholars have argued that sexual desire plays a major role not only in attracting potential partners to each other but also in encouraging the formation of an attachment between them (Birnbaum, 2014; Hazan & Zeifman, 1994). These claims notwithstanding, at present there is no direct evidence demonstrating whether sexual desire motivates the attachment-bonding process in initial encounters or, as an alternative, whether emotional bonding develops independent of desire.

Few studies have addressed the possibility that activation of the sexual system has systematic effects on the motivation to engage in nonsexual but relationship-promoting behaviors (e.g., self-disclosure, sacrificing for the partner; Birnbaum et al., 2017; Gillath, Mikulincer, Birnbaum, & Shaver, 2008). A limitation is that these studies relied mainly on either hypothetical beliefs about dyadic interactions or online interactions. The present research used ecologically valid designs with face-to-face interactions to demonstrate that activation of the sexual system encourages the enactment of nonsexual behaviors that signal warmth and contact readiness (i.e., nonverbal behaviors, such as close physical proximity and frequent eye contact, which indicate interest in further contact) and thereby foster relationship initiation.

The relationship-promoting function of sex

Evolutionary theorizing argues that the sexual behavioral system evolved to facilitate reproduction; one way it does so is by generating sexual desire that manifests itself in approaching desirable partners and enticing them to engage in sexual activity (Birnbaum et al., 2014; Buss & Kenrick, 1998). As such, the basic functioning of the sexual system is not dependent on attachment processes (i.e., people can mate without bonding; Diamond, 2013). Nevertheless, the prolonged helplessness of human offspring promoted the development of mechanisms that keep sexual partners bonded to each other so that they can jointly care for their offspring and thereby improve their survival chances (Diamond, 1998; Fletcher, Simpson, Campbell, & Overall, 2015).

Several characteristics of human sexuality suggest that behavioral manifestations of the sexual system may act as such a mechanism, cultivating protracted intimate contact and enduring attachment between sexual partners (Birnbaum, 2018; Birnbaum & Finkel, 2015; Hazan & Zeifman, 1994). Humans, for example, typically have sex privately; prefer the “missionary position,” which enables face-to-face contact; and cuddle and sleep together after sex (Ford & Beach, 1951; Reinisch & Beasley, 1991). In support of this theorizing, neuroimaging research has revealed that similar brain regions (e.g., the caudate, insula, putamen) are activated during experiences of sexual desire and romantic love (Cacioppo & Cacioppo, 2013; Diamond & Dickenson, 2012). This pattern hints at a neurobiological pathway through which sexual activation (i.e., excitation of the neural processes that underlie sexual response) can influence emotional bonding. Indeed, people show greater accessibility of intimacy-related thoughts following subliminal exposure to sexual stimuli (vs. neutral stimuli; Gillath et al., 2008) and generally acknowledge that they sometimes engage in sex as a means of initiating romantic relationships with potential partners and nurturing the emotional connection within existing relationships (Birnbaum & Gillath, 2006; Birnbaum & Reis, 2006).

Beyond associating sex with attachment formation and maintenance, people also act accordingly by being more inclined to use strategies that instill a sense of intimacy with prospective sexual partners (e.g., disclosing intimate personal information) or with current sexual partners (e.g., resolving conflicts constructively) following sexual priming (Birnbaum et al., 2017; Gillath et al., 2008). Overall, as suggested by longitudinal studies, sex may operate as an attachment-facilitating process that encourages investment in current relationships. For example, heightened feelings of passion for one’s partner and gratifying sex are associated with relationship-enhancing behaviors, such as displays of intimacy and affection (Birnbaum, Reis, Mikulincer, Gillath, & Orpaz, 2006; Debrot, Meuwly, Muise, Impett, & Schoebi, 2017; Rubin & Campbell, 2012). Furthermore, sexual satisfaction tends to create an “afterglow” for as long as 48 hr following sexual activity and thereby helps to sustain emotional bonds between episodes of sexual interaction (Meltzer et al., 2017).

The present research

Relying on the theorizing that the sexual system has been coopted by evolutionary processes to promote enduring bonds between romantic partners (Birnbaum, 2018; Eastwick & Finkel, 2012), the present research sought to provide direct evidence for the hypothesis that activation of the sexual system elicits not only sexual advances and approach tendencies but also specific nonsexual behaviors that foster relationship initiation. Recent research investigating the effects of sexual priming on relationship goal pursuit has already found that people reveal more personal information to a prospective partner following activation of the sexual behavioral system (Birnbaum et al., 2017). In the present studies, we aimed to extend this research by exploring whether sexual activation during initial face-to-face encounters with a potential partner predicts the enactment of other verbal relationship-promoting behaviors as well as nonverbal behaviors that signal warmth and contact readiness. We hypothesized that sexual activation would facilitate the enactment of relationship-initiating behaviors, which, in turn, would predict heightened interest in dating this partner.

Four studies tested this hypothesis. Study 1 examined whether sexual desire for a potential partner is associated with self-reported and objectively coded immediacy behaviors. Specifically, participants mimed together with an attractive opposite-sex confederate to prerecorded music while being videotaped and then rated their desire for the confederate. Judges rated the extent to which participants enacted immediacy behaviors toward the confederates (e.g., proximity seeking, eye contact) and were behaviorally synchronized with them. Study 2 sought to replicate and extend the findings of Study 1 by investigating whether desire for potential partners is associated with being synchronized with them, which in turn, would predict interest in dating them. For this purpose, participants slow danced with an opposite-sex confederate and then rated their desire for the confederate, the extent to which they were synchronized with each other, and their interest in seeing the confederate again.

Studies 3 and 4 were designed to establish a causal connection between sexual activation and nonsexual behaviors (provision of responsiveness and help, respectively) that are not only strategically employed to initiate relationships with potential partners (Bell & Daly, 1984; Birnbaum & Reis, 2012) but also play a key role in supporting long-term bonding. Indeed, synchronization and similar immediacy behaviors (e.g., mimicry), which were the focus of Studies 1 and 2, are not necessarily aimed at long-term relationship goals (van Straaten, Engels, Finkenauer, & Holland, 2008). Provision of responsiveness and help, in contrast, is the linchpin of attachment processes (Clark & Aragon, 2013; Reis & Clark, 2013) and thus is less likely to be strategically enacted for the sheer sake of engaging in sex. In both studies, participants were exposed to sexual stimuli (versus neutral stimuli) and then interacted face-to-face with an attractive opposite-sex stranger who either discussed interpersonal dilemmas with them (Study 3) or ostensibly sought their help (Study 4). Participants’ responsiveness and helping behaviors toward the confederate were recorded.

Study 1

Study 1 sought to examine whether desire for a new acquaintance would be associated with enactment of nonverbal immediacy behaviors that indicate contact readiness (e.g., synchronization, close physical proximity, frequent eye contact; Andersen, 1985; Eibl-Eibesfeldt, 1989). To do so, participants mimed together with an attractive opposite-sex confederate to prerecorded music while being videotaped and then rated their desire for the confederate. In addition, participants, confederates, and independent judges rated the extent to which the participants and confederate were synchronized with each other during this lip-sync performance. Judges also rated participants’ other overt nonverbal expressions of contact readiness.

Method

Participants

Fifty-eight students (36 women, 22 men) from a university in central Israel volunteered for the study without compensation. Sample size was determined via a priori power analysis using G*Power software package (Faul, Erdfelder, Buchner, & Lang, 2009) to ensure 80% power to detect an effect size, ρ, of 0.35 at p < .05. This hypothesized effect size was based on previous research examining the association of sexual priming with another relationship-initiation behavior (self-disclosure; Birnbaum et al., 2017). Participants ranged from 20 to 31 years of age (M = 24.03, SD = 2.11). Years of education ranged from 12 to 20 years (M = 12.43, SD = 2.52). All participants were heterosexual and not currently involved in a romantic relationship.

Measures and procedure

Participants who agreed to participate in a study of mutual activities were individually scheduled to attend a single half-hour laboratory session. Upon arrival, participants were greeted by a research assistant and told that they would be participating in a lip-sync performance in which they and another participant would mime together to prerecorded music (without actually singing) while being videotaped. All participants were assigned an attractive opposite-sex confederate who was trained to perform certain movement (e.g., waving hands, running a hand through his/her hair) at fixed times throughout the song.

The confederates’ sexual desirability was assessed prior to participating in the study to ensure that both were moderately desirable. Specifically, 10 female and 10 male judges were shown a photo of the opposite-sex confederate and asked to evaluate the confederate’s sexual desirability on five adjectives used by Birnbaum, Weisberg, and Simpson (2011): sexually desirable, sensual, “hot,” attractive, and sexually exciting (e.g., “To what extent do you think that the person in the photo is sexually desirable?”). Ratings were made on a 5-point scale ranging from not at all (1) to very much (5). The desirability average ratings were moderately high for both the female confederate (M = 3.38, SD = .27) and the male confederate (M = 3.25, SD = .35). There were no significant gender differences in desirability, t(18) = 0.93, p = .364.

The participants and the confederate were then asked to rehearse their performance for a few minutes by listening to the song “I kissed a girl,” which was recorded by the popular singer Katy Perry, and read its lyrics. Then, the research assistant instructed them to start their lip-sync performance and left the room. All performances were videotaped by two cameras mounted in the corners of the room. After 1 min, the research assistant returned and ended the performance.

Following the lip-sync performance, participants evaluated the confederate’s sexual desirability on five adjectives, which were used in the pretest described above (Birnbaum, Weisberg, & Simpson, 2011; α = .93). Participants and confederates also completed 3 items assessing their perceptions of being synchronized with each other (“To what extent were you and the other participant synchronized with each other during the lip-sync performance?”; “To what extent did you and the other participant attend to each other’s body language during the lip-sync performance?”; αs = .66 and .92 for participants and confederates, respectively). Ratings were made on a 5-point scale ranging from 1 (not at all) to 5 (very much so). Finally, participants provided demographic information (age, relationship status) and were then fully debriefed.

Coding synchronization and immediacy behaviors

The video-recorded performances were coded by two trained independent judges (psychology students) who were blind to the hypotheses. Each judge watched the performances and rated each participant’s overt nonverbal expressions of contact readiness (i.e., behaviors that signal warmth and immediacy: close physical proximity, frequent eye contact, flashing smiles; Andersen, 1985; Eibl-Eibesfeldt, 1989; Leck & Simpson, 1999) in a single overall coding of displays of immediacy behavior. Judges also coded participants’ tendency to synchronize with the confederate and mimic their body language (e.g., moving at the same rhythm, making similar dance movements). Ratings were made on a 5-point scale ranging from 1 (not at all) to 5 (very much). Intraclass correlation coefficients (ICC) for immediacy behavior and synchronization were 0.73 and 0.72, respectively. Hence, judges’ ratings were averaged for each participant.

Results and discussion

As Table 1 shows, participant’s desire for the confederate was positively associated with coded immediacy behaviors as well as with synchronization as perceived by participants, confederates, and raters. These findings suggest that sexual activation, which is naturally experienced when a desirable potential partner is met on a date, elicits nonverbal behaviors that convey contact readiness. And yet, the participants’ and judges’ perceptions of synchronization were not significantly associated, which might be due to the low reliability of the perception of synchronization measure. Future studies should use a more reliable measure of perception of synchronization, which includes more items. Importantly, gender did not interact with manifestations of sexual activation in predicting relationship initiating behaviors in any of the studies.

Table 1.

Correlation among participant’s desire for the confederate, synchronization, and immediacy behaviors (Study 1).

	2	3	4	5	Mean	SD
1. Participant’s desire for confederate	.30*	.40**	.27*	.36**	3.34	0.86
2. Participants’ perception of synchronization	—	.46***	.14	.29*	3.10	0.73
3. Confederates’ perception of synchronization		—	.58***	.60***	3.24	1.00
4. Coded synchronization			—	.77***	2.39	1.05
5. Coded immediacy behavior				—	2.77	0.93

Note. N = 58. All measures were rated on a 5-point Likert-type scale.

*p < .05; **p < .01; ***p < .001.

Study 2

Study 2 was designed to replicate the findings of Study 1 with a different methodology that requires more intimate coordination (slow dance rather than lip-sync performance) and is thus more relevant to romantic contexts. Furthermore, Study 2 sought to extend Study 1 by adding a measure of interest in future interactions with potential partners and testing the prediction that sexual desire for these partners would be associated with greater synchronization with them, which, in turn, would predict heightened interest in further interactions. Past research has already shown that mimicry is used in interpersonal contexts to cultivate affiliation and attraction (e.g., Gueguen, 2009; Lakin & Chartrand, 2003). In Study 2, we wished to demonstrate that sexual activation can facilitate this process, such that a more complete picture of the dynamics of emerging relationships involves heightened sexual desire for a potential partner that encourages the enactment of behaviors, such as synchronization, that engender interpersonal closeness. These behaviors, in turn, should further increase the desire for this person and thereby foster relationship development. Specifically, participants performed a slow dance with an opposite-sex confederate. Then, participants rated their desire for the confederate, the extent to which they were synchronized while dancing, and their desire for further interactions.

Method

Participants

Eighty students (38 women, 42 men) from a university in central Israel volunteered for the study without compensation. Following Fritz and MacKinnon’s (2007) suggestion, sample size was determined via a priori power analysis using PowMedR in R (Kenny, 2013) to ensure 80% power for testing an indirect effect in a mediation analysis if both paths a and b had medium-sized effects. Participants ranged from 18 to 34 years of age (M = 24.34, SD = 2.46). Years of education ranged from 11 to 18 years (M = 12.43, SD = 3.43). All participants were heterosexual and not currently involved in a romantic relationship.

Measures and procedure

Participants who signed up for a study of mutual activities were individually scheduled to attend a single half-hour laboratory session. Upon arrival, participants were greeted by a research assistant and told that they would be dancing with another participant. All participants were assigned an opposite-sex confederate whose attractiveness was assessed prior to participating in the study to ensure that both were moderately desirable, using the same procedure described in Study 1. The desirability average ratings were moderately high for both the female confederate (M = 3.00, SD = .22) and the male confederate (M = 3.08, SD = .23). There were no significant gender differences in desirability, t(18) = 0.79, p = .437. The participant and confederate were escorted to the same room by a research assistant, who instructed them to perform a slow dance together for a couple of minutes while listening to the song, “I don’t want to miss a thing” (recorded by the band “Aerosmith”). Then, the research assistant placed the participant and confederate in a slow-dancing position, turned on the music, and left the room. After 2 min, the research assistant returned and asked participants to end their dance and led the confederate to another room.

Following the dancing session, participants rated their desire for the confederate (α = .94) and their perceptions of being synchronized with the confederate (α = .85). Both measures were identical to those used in Study 1. Participants also completed 3 items assessing their interest in future interactions with the confederate (“To what extent would you like to date the other participant?”; α = .93). Ratings were made on a 5-point scale ranging from 1 (not at all) to 5 (very much so). Finally, participants were asked to provide demographic information and were then fully debriefed.

Results and discussion

To examine whether the effect of participant’s desire for the confederate on interest in future interactions was mediated by perception of synchronization, we used PROCESS (Hayes, 2013, model 4), in which participant’s desire for the confederate was the predictor, interest in future interactions with the confederate was the outcome measure, and perceived synchronization was the mediator. Figure 1 shows the final model. This analysis revealed a significant effect of participant’s desire for the confederate on synchronization (b = .46, SE = .09, t = 4.83, p < .001, β = .48, 95% CI [.28, .68]). The analysis further revealed a significant effect of synchronization on interest in future interactions (b = .64, SE = .10, t = 6.14, p < .001, β = .57, 95% CI [.39, .75]), such that the greater the synchronization the participants experienced with the confederates, the greater their interest in future interactions with them.

Figure 1.

Mediation model showing that perceptions of synchronization with the confederates mediated the association between participants’ desire for the confederates and interest in future interaction with them in Study 2. Note. Path coefficients are standardized. The value in parentheses is from the analysis of the effect without synchronization in the equation. ***p < .001.

Results also indicated that the 95% CI of the indirect effect for participant’s desire for the confederate as a predictor of interest in future interaction with the confederates through synchronization did not include zero and thus is considered significant (b = .13, SE = .05, t = 2.72, p = .006, β = .12, 95% CI [.04, .25], 5,000 bootstrapped samples). Finally, synchronization was uniquely associated with interest in future interactions after controlling for participant’s desire for the confederate (b = .29, SE = .08, t = 3.37, p < .001, β = .26, 95% CI [.12, .40]). Overall, the analyses supported a mediational pathway, such that desire for the confederates was associated with increased synchronization with them, which in turn, predicted greater interest to see them again. Nevertheless, because Studies 1 and 2 were correlational, we could not rule out the possibility that people who exhibit more relationship-initiating behaviors tend to perceive new potential partners as more desirable rather than the other way around. Study 3 was designed to address this limitation.

Study 3

Study 3 sought to establish a causal connection between activation of the sexual behavior system and enactment of relationship-initiating behaviors. To activate the sexual system, we used a subliminal priming technique, which bypasses conscious evaluation of sexual stimuli and is therefore less likely to evoke deliberate motivational biases when participants interact with a potential partner (Gillath, Mikulincer, Birnbaum, & Shaver, 2007; Gillath et al., 2008). Study 3 also sought to extend Studies 1 and 2 by exploring whether the predicted effect of activation of the sexual system on relationship initiation would be found in behaviors that signal not only mere proximity seeking but also caring about a partner’s well-being (Reis & Clark, 2013). Expressing caring, which is a hallmark of communal relationships (Clark & Aragon, 2013), is one important way that people signal their relationship interest to each other. Specifically, participants were subliminally exposed to sexual stimuli (versus neutral stimuli) and then discussed several interpersonal dilemmas with an opposite-sex participant whom they did not know while being videotaped. Judges rated the extent to which participants engaged in behaviors that conveyed responsiveness and caring to the confederate during the interactions.

Method

Participants

Eighty-four undergraduate students (42 women, 42 men) from a university in central Israel volunteered for the study without compensation. To determine sample size, we estimated the relative power for the planned multilevel analysis using the PinT V2.1 computer program (Bosker, Snijders, & Guldemond, 2003). Power for a random coefficient model was estimated for a sample of 42 couples, with a moderate effect size (.30 in a correlation metric). Estimation of the standard errors assuming α = .05 yielded a power of .80. All participants were heterosexual and were not currently involved in a romantic relationship. Participants ranged from 21 to 31 years of age (M = 24.05, SD = 1.82). Years of education ranged from 12 to 17 years (M = 12.62, SD = 2.04).

Measures and procedure

Participants were invited to take part in a study on preferences and attitudes. Participants who agreed to participate were randomly paired with an unfamiliar opposite-sex participant and scheduled to attend a single half-hour laboratory session. Prior to each session, participants were randomly assigned to one of two conditions: Being subliminally exposed to a sexual or a neutral prime (both participants in a session were assigned to the same condition). Upon arrival, the two participants were led into separate rooms to ensure confidentiality. Then, the session followed the subliminal activation of the sexual system computerized task, which was used by Birnbaum et al.’s (2017, Study 1).

Participants were told that they should indicate their preferences across seven categories by choosing one of two options from each category (each category was represented by three pairs of options): food (e.g., Italian, Thai), pets (e.g., cats, dogs), music (e.g., pop, rock), drinks (e.g., alcoholic, nonalcoholic), recreation (e.g., party, pub), color (e.g., red, blue), and season (e.g., summer, winter). Before each pair of options, participants were exposed to either a sexual or a neutral prime, which was presented subliminally (for 30 milliseconds [ms]). Presentation of the prime was followed by a mask presented for 500 ms (a visual “noise” pattern that erased the prime’s image on the retina), and then by the pair of two options, separated by a hyphen (e.g., pop—rock). Overall, the sexual or neutral primes appeared 21 times; once before each of the 21 pairs of options. The sexual primes, used by Gillath, Mikulincer, Birnbaum, and Shaver (2008), were erotic but not pornographic pictures (an attractive naked, reclining man shown from the groin up for female participants; an attractive, naked, kneeling woman photographed from behind for male participants). Neutral primes were landscapes.

Following this procedure, participants were reunited and invited to communicate face-to-face for 2 min to get to know each other by following a set of standard questions about their hobbies, positive traits, and future career plans. Then, participants were asked to discuss several interpersonal dilemmas (e.g., “Are you for or against playing ‘hard to get’ at the start of a relationship?”). All interactions, which lasted 5–7 min, were videotaped by two cameras mounted in the corners of the room, with one camera pointed at each interlocutor at an angle to allow for full frontal recording. After the discussion, participants provided demographic information and were then fully debriefed.

Coding of enacted responsiveness during the discussion

The video-recorded interactions were coded by two trained independent judges (psychology students) who were blind to the hypotheses and experimental condition. Before making the ratings, judges were given detailed instructions and training on the rating procedure, which was based on the coding system used by Birnbaum et al. (2016). This coding system, which was derived from Reis and Shaver’s (1988) model of responsiveness, operationalizes responsive behaviors as behaviors that signal understanding (i.e., listening, gathering information, and getting the facts right), validation (i.e., reinforcing the partner’s self-views and making the partner feel valued and respected), and caring (i.e., communicating affection for one’s partner). Each judge watched the discussions and rated the extent to which the participant employed these behaviors during the interaction, using a 5-point Likert-type scale ranging from 1 (not at all) to 5 (a great deal). Inter-rater reliability was adequate (ICC = 0.70). Judges’ ratings were averaged for each participant to create a measure of global responsive behaviors.

Results and discussion

Because participants were nested within dyads, we used multilevel analysis to examine the effect of sexual priming on enacted responsiveness while controlling for dependencies in partners’ responsiveness to each other. In line with our hypothesis, responsiveness was significantly higher in the sexual priming condition (M = 3.45, SD = .83) than in the neutral condition (M = 2.97, SD = .78; b = .48, SE = .19, t(40) = 2.50, p = .016, 95% CI [.09, .86]). These findings support our prediction of a causal connection between activation of the sexual system and engagement in relationship-initiating behaviors, as manifested in provision of responsiveness to a potential partner during face-to-face interactions.

Study 4

In Study 4, we sought to activate the sexual system in a more ecologically valid manner, investigating how sexual stimuli in real-life settings (watching videos) affect engagement in other approach behavior that may facilitate relationship initiation more actively than provision of responsiveness (Bell & Daly, 1984). Specifically, participants were supraliminally exposed to sexual stimuli (versus neutral stimuli) and then interacted with an attractive opposite-sex confederate who ostensibly sought their help. Participants’ helping behaviors toward the confederate were recorded.

Method

Participants

One hundred undergraduate students (50 women, 50 men) from a university in central Israel volunteered for the study without compensation. Sample size was determined via a priori power analysis using the G*Power software package (Faul et al., 2009) to ensure 80% power to detect an effect size, d, of 0.50 at p < .05. All participants were heterosexual and were not currently involved in a romantic relationship. Participants ranged from 18 to 29 years of age (M = 24.43, SD = 2.03). Years of education ranged from 12 to 20 years (M = 13.50, SD = 1.67).

Measures and procedure

Participants who agreed to participate in a study on the effects of watching different film genres on cognitive and interpersonal skills were individually scheduled to attend a single half-hour laboratory session. Prior to each session, participants were randomly assigned to one of two conditions: Being supraliminally exposed to a sexual or a neutral prime. Upon arrival, participants were greeted by an experimenter and were asked to watch either an erotic (but not pornographic) video or a neutral video. The erotic video depicted a scene from the movie “The boy next door,” in which the actors Jennifer Lopez and Ryan Guzman are having sexual intercourse. The neutral video depicted rainforests in South America and was chosen because it was judged to be free of sexual and emotional connotations. Each video was 3:40 min long.

After watching the video, participants completed 3 items assessing their sexual arousal (e.g., “To what extent are the videos sexually arousing?”; “To what extent are you sexually aroused now?”; “To what extent did the videos elicit sexual thoughts?”; α = .75). These items were intermixed with three fillers assessing interest in neutral activities (e.g., “To what extent would you be interested in talking to a friend now?”; “To what extent would you be interested in exercising now?”; “To what extent would you be interested in watching a documentary movie now?”) to mask the nature of this questionnaire. Ratings were made on a 5-point scale ranging from 1 (not at all) to 5 (very much so).

Then, participants were led to believe that in the next 5 min, they and another participant would complete a verbal reasoning task. In reality, all participants were assigned an attractive opposite-sex confederate who was blind to their experimental condition. The confederates’ attractiveness was assessed prior to participating in the study to ensure that both were moderately desirable, using the same procedure described in Study 1. The desirability average ratings were moderately high for both the female confederate (M = 3.19, SD = .23) and the male confederate (M = 3.33, SD = .26). There were no significant gender differences in desirability, t(18) = 1.27, p = .218. The experimenter introduced participants to the confederate, seated them next to each other, told both that they were allowed to speak with each other while completing the task, and left the room.

When the confederate ostensibly got to the third question (approximately 2 min after the experimenter had left the room), he or she turned to the participant and asked for help in solving that question, uttering, “I’m stuck with this question. Could you please help me in solving it?” Participants’ helping behaviors toward the confederate were recorded by the confederate, using the following measures: Time elapsed until participants started providing help to the confederate (in seconds) and actual time spent helping solve the needed question (in seconds), which were measured using a stopwatch hidden in the confederates’ pocket, and the quality of the given help, as assessed by 5 items, which were completed by the confederate following this session (e.g., “To what extent was the participant helpful?”; “To what extent was the help effective?”; α = .81). Ratings were made on a 5-point scale ranging from 1 (not at all) to 5 (very much so). After 5 min, the experimenter returned to the room and asked participants to stop working. Participants then provided demographic information and were fully debriefed.

Results and discussion

Manipulation check

A t-test on sexual arousal yielded the expected effect, t(98) = 2.57, p = .012, Cohen’s d = .51, 95% CI [.11, .91]: Sexual arousal was higher in the sexual priming condition (M = 2.69, SD = 1.03) than in the neutral condition (M = 2.22, SD = .75). Gender did not interact with sexual activation in predicting sexual arousal, F(1, 96) = .20, p = .652, η² = .002.

The effect of sexual activation on provision of help to an opposite-sex stranger

To determine whether differences existed between conditions in time elapsed until help was provided and duration and quality of help, a one-way multivariate analysis of variance (MANOVA) for sexual priming conditions was performed on these three measures. This MANOVA yielded a significant difference between sexual activation conditions, Hotelling’s Trace = 0.66, F(3, 96) = 21.19, p < .001, η² = .398, 95% CI [.23, .51]. Univariate analyses indicated that this effect was significant for all three measures, such that participants were quicker to help, invested more time in helping, and were perceived as more helpful in the sexual activation condition than in the control condition (see Table 2 for relevant statistics).

Table 2.

Means, standard deviations, statistics, and effect sizes of provision of help for the experimental conditions (Study 4).

	Sexual activation	Control	F(1, 98)	η²	95% CI for η²
Quality of help	3.49 (0.87)	2.17 (0.78)	62.92***	.391	[.24, .51]
Time elapsed till help was provided	1.44 (1.11)	2.02 (1.36)	5.34*	.052	[.01, .16]
Duration of help	11.73 (12.83)	6.33 (8.27)	6.24*	.060	[.01, .17]

Note. N = 100. Quality of help was rated on a 5-point Likert-type scale; time elapsed until help was provided and duration of help were measured in seconds. Standard deviations are presented in parentheses.

*p < .05; ***p < .001.

As expected, a t-test on the average of the three filler items did not yield a significant effect, t(98) = 0.72, p = .472, Cohen’s d = .14 95% CI [−.25, .54]. Interest in neutral activities was not significantly different in the sexual priming (M = 1.46, SD = .83) and neutral conditions (M = 1.34, SD = .82), suggesting that the manipulation did not affect interest in nonsexual activities. A t-test on the single filler item that assessed interest in talking to a friend was not significant either, suggesting that the approach system was not broadly activated with the sexual system. It therefore seems that sexual activation increases the desire to bond specifically with a potential sexual partner rather than with any person.

General discussion

Sexual desire is theorized to be a vital force that attracts romantic couples and unites them throughout relationship development (Birnbaum & Finkel, 2015; Birnbaum & Reis, 2019). And yet, sexual desire should be most important as a relationship promoter in earlier stages, when it is often the primary motivation for pursuing a relationship (Birnbaum, 2018; Poulsen, Holman, Burney, & Carroll, 2013). Nevertheless, thus far it has been unclear whether desire motivates merely reproductive acts, with attachment developing independently, or whether desire directly contributes to the building of an emotional bond between newly acquainted partners. Indeed, although the behavioral manifestations of the attachment and sexual mating systems may occur independently (Bowlby, 1969/1982; Diamond, 2003), evolutionary and social processes may have rendered humans particularly likely to become romantically attached to partners to whom they are sexually attracted (Diamond, 2013).

In four studies, we provided support for the latter option, demonstrating that sexual desire elicits behaviors that can facilitate the attachment-bonding process during face-to-face encounters with a new opposite-sex acquaintance. Study 1 showed that participants who interacted with a confederate perceived to be desirable exhibited more immediacy behaviors toward this confederate (synchronization, eye-contact). Study 2 extended these findings, indicating that participant’s desire for the confederates was associated with being synchronized with them, which in turn, predicted greater interest in dating them. Studies 3 and 4 established a causal connection between activation of the sexual system and engagement in relationship-promoting behaviors (provision of responsiveness and help, respectively).

Prior research has already shown that activation of the sexual system leads people to disclose personal information to prospective partners (Birnbaum et al., 2017), possibly in an attempt to become closer to them. Our studies here add to this research by demonstrating that activation of the sexual system elicits other verbal and nonverbal behaviors that not only convey contact readiness but also express caring about a partner’s well-being. By doing so, our research suggests that when two strangers meet, sexual desire experienced by one or both of them may initiate a cascade of behaviors that signal their interest in further interaction as well as their willingness to invest in a potential relationship. Such behaviors help set the stage for deepening the emotional connection between them. To be sure, whereas intense desire may attract new partners to each other (Berscheid & Reis, 1998), the behaviors it engenders are those that support long-term bonding (Reis & Clark, 2013).

Of course, relationship-promoting behaviors in this context may be motivated by short-term rather than long-term relationship goals. Indeed, although short- and long-term relationships may often seem indistinguishable in their initial phases of development (Eastwick, Keneski, Morgan, McDonald, & Huang, 2018), some people may still behave deceitfully toward potential partners while being sexually aroused in order to have sex (Ariely & Loewenstein, 2006) and thus may strategically provide responsiveness or help to obtain sexual favors (Birnbaum, Ein-Dor, Reis, & Segal, 2014; Haselton, Buss, Oubaid, & Angleitner, 2005). Unfortunately, one limitation of the present research is the failure to assess the motives behind engaging in relationship-promoting manner. Thus, it remains unclear whether being more responsive or helpful in this context is motivated by long-term or by short-term relationship goals. Future research should assess the reasons for engaging in relationship-initiating behaviors in order to examine how these reasons affect the unfolding of emerging relationships over time.

More research is also needed to examine the conditions under which heightened relationship-promoting tendencies in a sexually arousing context reflect the desire for a meaningful relationship with a prospective partner and predict greater efforts toward building an intimate relationship. For example, research should explore whether sexual attraction that is based on partner’s surface-quality traits (e.g., physical attractiveness) elicits different relationship goals (short-term vs. long-term) than sexual attraction that is based on deeper-quality traits, which tap relationship compatibility (e.g., emotional stability, sensitivity), and whether these different goals, in turn, generate distinctive constellations of relationship-initiating behaviors (e.g., immediacy behaviors in the case of both short-term and long-term goals vs. more attachment-promoting behaviors in the case of long-term goals).

Another limitation of our research is that in Studies 3 and 4, we compared sexual with neutral primes and did not control for general closeness priming. It is therefore unclear whether engagement in relationship initiating behaviors is exclusive to sexual priming. Future research should rule out the possibility that priming sexuality leads to higher levels of positive affect or to heightened feelings of engagement, which in turn, facilitate approach behavior toward a new interaction partner. Such an additional study could explore, for example, whether priming sexuality induces responsiveness to strangers of the desired sex rather than to both male and female strangers. Finally, our samples were mainly composed of young Israeli students who experienced brief interactions in an artificial lab setting. Future studies should investigate whether the findings generalize to more naturalistic settings (e.g., pickups, first dates) and will replicate with more varied samples, such as diverse ethnic groups or older individuals whose attractions may be more sensitive to deeper traits.

Notwithstanding these limitations, our research demonstrates that even a primed, nonconscious sexual stimulus can facilitate engagement in intimacy-promoting behaviors within the context of initial encounters. Prior research, which focused on influences in the reverse direction, namely from intimacy to sexual processes, has revealed that expressions of intimacy may instigate desire between new acquaintances (Birnbaum & Reis, 2012; Birnbaum et al., 2014). The present research extends these findings, suggesting that the complete dynamics of emerging relationships between previously unacquainted strangers may entail experiencing sexual desire that facilitates the enactment of behaviors that cultivate interpersonal closeness. These behaviors, in turn, may heighten the experience of desire between partners and help to build their evolving emotional bond. In this manner, sexual desire may play a causally important role in the development of relationships.

Footnotes

Authors’ note

Moran Mizrahi is now affiliated with Ariel University Center of Samaria, Israel.

Acknowledgements

The authors would like to thank Nir Klar, Noam Hadadi, Adam Lazovski, Dafi Hadas, Lior Barbi-Ilan, Reem Ilan, Coral Kratenstein, and Yarden Barbi for their assistance in the collection of the data as well as Kobi Zholtack, Mor Yaacov, Shiran Arinus, Amit Ben-Zvi, Sivan Shapiro-Got, Romy Orr, and Maayan Nagar for their assistance in conducting the research.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported by the Israel Science Foundation (grants 86/10 and 1210/16 awarded to Gurit E. Birnbaum) and by the Binational Science Foundation (grants #2011381 and #2016405 awarded to Gurit E. Birnbaum and Harry T. Reis).

ORCID iD

Gurit E. Birnbaum

Moran Mizrahi

Open research statement

This research was not preregistered. The data and materials used in the research are available upon request by emailing birnbag@gmail.com.

References

Andersen

P. A.

(1985). Nonverbal immediacy in interpersonal communication. In Siegman

A. W.

Feldstein

(Eds.), Multichannel integrations of nonverbal behavior (pp. 1–36). Hillsdale, NJ: Erlbaum.

Ariely

Loewenstein

(2006). The heat of the moment: The effect of sexual arousal on sexual decision making. Journal of Behavioral Decision Making, 19, 87–98.

Bell

R. A.

Daly

J. A.

(1984). The affinity-seeking function of communication. Communication Monographs, 51, 91–115.

Berscheid

Reis

H. T.

(1998). Attraction and close relationships. In Gilbert

D. T.

Fiske

S. T.

Lindzey

(Eds.), The handbook of social psychology (Vol. 2, pp. 193–281). New York, NY: McGraw-Hill.

Birnbaum

G. E.

(2014). Sexy building blocks: The contribution of the sexual system to attachment formation and maintenance. In Mikulincer

Shaver

P. R.

(Eds.), Mechanisms of social connection: From brain to group (pp. 315–332). Washington, DC: American Psychological Association.

Birnbaum

G. E.

(2018). The fragile spell of desire: A functional perspective on changes in sexual desire across relationship development. Personality and Social Psychology Review, 22, 101–127.

Birnbaum

G. E.

Ein-Dor

Reis

H. T.

Segal

(2014). Why do men prefer nice women over bad ones? Gender typicality mediates the effect of responsiveness on perceived attractiveness in initial acquaintanceships. Personality and Social Psychology Bulletin, 40, 1341–1353.

Birnbaum

G. E.

Finkel

E. J.

(2015). The magnetism that holds us together: Sexuality and relationship maintenance across relationship development. Current Opinion in Psychology, 1, 29–33.

Birnbaum

G. E.

Gillath

(2006). Measuring subgoals of the sexual behavioral system: What is sex good for? Journal of Social and Personal Relationships, 23, 675–701.

10.

Birnbaum

G. E.

Mikulincer

Szepsenwol

Shaver

P. R.

Mizrahi

(2014). When sex goes wrong: A behavioral systems perspective on individual differences in sexual attitudes, motives, feelings, and behaviors. Journal of Personality and Social Psychology, 106, 822–842.

11.

Birnbaum

G. E.

Mizrahi

Kaplan

Kadosh

Kariv

Tabib

… Burban

(2017). Sex unleashes your tongue: Sexual priming motivates self-disclosure to a new acquaintance and interest in future interactions. Personality and Social Psychology Bulletin, 43, 706–715.

12.

Birnbaum

G. E.

Reis

H. T.

(2006). Women’s sexual working models: An evolutionary-attachment perspective. The Journal of Sex Research, 43, 328–342.

13.

Birnbaum

G. E.

Reis

H. T.

(2012). When does responsiveness pique sexual interest? Attachment and sexual desire in initial acquaintanceships. Personality and Social Psychology Bulletin, 38, 946–958.

14.

Birnbaum

G. E.

Reis

H. T.

(2019). Evolved to be connected: The dynamics of attachment and sex over the course of romantic relationships. Current Opinion in Psychology, 25, 11–15.

15.

Birnbaum

G. E.

Reis

H. T.

Mikulincer

Gillath

Orpaz

(2006). When sex is more than just sex: Attachment orientations, sexual experience, and relationship quality. Journal of Personality and Social Psychology, 91, 929–943.

16.

Birnbaum

G. E.

Reis

H. T.

Mizrahi

Kanat-Maymon

Sass

Granovski-Milner

(2016). Intimately connected: The importance of partner responsiveness for experiencing sexual desire. Journal of Personality and Social Psychology, 111, 530–546.

17.

Birnbaum

G. E.

Weisberg

Y. J.

Simpson

J. A.

(2011). Desire under attack: Attachment orientations and the effects of relationship threat on sexual motivations. Journal of Social and Personal Relationships, 28, 448–468.

18.

Bosker

R. J.

Snijders

T. A. B.

Guldemond

(2003). PINT (Power IN Two-level designs): Estimating standard errors of regression coefficients in hierarchical linear models for power calculations (user’s manual, version 2.1). Retrieved from http://stat.gamma.rug.nl/snijders/

19.

Bowlby

(1969/1982). Attachment and loss: Vol. 1. Attachment (2nd ed.). New York, NY: Basic Books.

20.

Buss

D. M.

Kenrick

D. T.

(1998). Evolutionary social psychology. In Gilbert

D. T.

Fiske

S. T.

Lindzey

(Eds.), Handbook of social psychology (Vol. 2, pp. 982–1026). New York, NY: McGraw-Hill.

21.

Cacioppo

J. T.

(2013). Lust for life. Scientific American Mind, 24, 56–63.

22.

Clark

M. S.

Aragon

O. R.

(2013). Communal (and other) relationships: History, theory development, recent findings, and future directions. In Simpson

J. A.

Campbell

(Eds.), The Oxford handbook of close relationships (pp. 255–280). New York, NY: Oxford University Press.

23.

Debrot

Meuwly

Muise

Impett

E. A.

Schoebi

(2017). More than just sex: Affection mediates the association between sexual activity and well-being. Personality and Social Psychology Bulletin, 43, 287–299.

24.

Diamond

(1998). Why is sex fun?: The evolution of human sexuality. New York, NY: Basic Books.

25.

Diamond

L. M.

(2003). What does sexual orientation orient? A biobehavioral model distinguishing romantic love and sexual desire. Psychological Review, 110, 173–192.

26.

Diamond

L. M.

(2013). Links and distinctions between love and desire. In Hazan

Campa

(Eds.), Human bonding (pp. 226–250). New York, NY: Guilford.

27.

Diamond

L. M.

Dickenson

(2012). The neuroimaging of love and desire: Review and future directions. Clinical Neuropsychiatry, 9, 39–46.

28.

Eastwick

P. W.

Finkel

E. J.

(2012). The evolutionary armistice: Attachment bonds moderate the function of ovulatory cycle adaptations. Personality and Social Psychology Bulletin, 38, 174–184.

29.

Eastwick

P. W.

Keneski

Morgan

T. A.

McDonald

M. A.

Huang

S. A.

(2018). What do short-term and long-term relationships look like? Building the Relationship Coordination and Strategic Timing (ReCAST) Model. Journal of Experimental Psychology: General, 147, 747–781.

30.

Eibl-Eibesfeldt

(1989). Human ethology. New York, NY: de Gruyter.

31.

Faul

Erdfelder

Buchner

Lang

A. G.

(2009). Statistical power analyses using G*Power 3.1: Tests for correlation and regression analyses. Behavior Research Methods, 41, 1149–1160.

32.

Fletcher

G. J. O.

Simpson

J. A.

Campbell

Overall

N. C.

(2015). Pair-bonding, romantic love, and evolution: The curious case of Homo sapiens. Perspectives on Psychological Science, 10, 20–36.

33.

Ford

C. S.

Beach

F. A.

(1951). Patterns of sexual behavior. New York, NY: Harper & Row.

34.

Fritz

M. S.

MacKinnon

D. P.

(2007). Required sample size to detect the mediated effect. Psychological Science, 18, 233–239.

35.

Gillath

Mikulincer

Birnbaum

G. E.

Shaver

P. R.

(2007). Does subliminal exposure to sexual stimuli have the same effects on men and women? The Journal of Sex Research, 44, 111–121.

36.

Gillath

Mikulincer

Birnbaum

G. E.

Shaver

P. R.

(2008). When sex primes love: Subliminal sexual priming motivates relational goal pursuit. Personality and Social Psychology Bulletin, 34, 1057–1069.

37.

Gueguen

(2009). Mimicry and seduction: An evaluation in a courtship context. Social Influence, 4, 249–255.

38.

Haselton

Buss

D. M.

Oubaid

Angleitner

(2005). Sex, lies, and strategic interference: The psychology of deception between the sexes. Personality and Social Psychology Bulletin, 31, 3–23.

39.

Hayes

A. F.

(2013). Introduction to mediation, moderation, and conditional process analysis. New York, NY: Guilford Press.

40.

Hazan

Zeifman

(1994). Sex and the psychological tether. In Bartholomew

Perlman

(Eds.), Advances in personal relationships: Attachment processes in adulthood (Vol. 5, pp. 151–177). London, UK: Jessica Kingsley.

41.

Kenny

(2013). PowMedR. R program to compute power of joint test for continuous exposure, mediator, and outcome. Retrieved from http://davidakenny.net/progs/PowMedR.txt

42.

Lakin

J. L.

Chartrand

T. L.

(2003). Using nonconscious behavioral mimicry to create affiliation and rapport. Psychological Science, 14, 334–339.

43.

Leck

Simpson

(1999). Feigning romantic interest: The role of self-monitoring. Journal of Research in Personality, 33, 69–91.

44.

Meltzer

A. L.

Makhanova

Hicks

L. L.

French

J. E.

McNulty

J. K.

Bradbury

T. N.

(2017). Quantifying the sexual afterglow: The lingering benefits of sex and their implications for pair-bonded relationships. Psychological Science, 28, 587–598.

45.

Poulsen

F. O.

Holman

T. B.

Burney

D. M.

Carroll

J. S.

(2013). Physical attraction, attachment styles, and dating development. Journal of Social and Personal Relationships, 30, 301–319.

46.

Reinisch

J. M.

Beasley

(1991). The Kinsey Institute new report on sex. London, UK: Penguin.

47.

Reis

H. T.

Clark

M. S.

(2013). Responsiveness. In Simpson

J. A.

Campbell

(Eds.), The Oxford handbook of close relationships (pp. 400–423). New York, NY: Oxford University Press.

48.

Reis

H. T.

Shaver

P. R.

(1988). Intimacy as an interpersonal process. In Duck

(Ed.), Handbook of research in personal relationships (pp. 367–389). London, UK: Wiley.

49.

Rubin

Campbell

(2012). Day-to-day changes in intimacy predict heightened relationship passion, sexual occurrence, and sexual satisfaction: A dyadic diary analysis. Social Psychological and Personality Science, 3, 224–231.

50.

van Straaten

Engels

R. C. M. E.

Finkenauer

Holland

R. W.

(2008). Sex differences in short-term mate preferences and behavioral mimicry: A semi-naturalistic experiment. Archives of Sexual Behavior, 37, 902–911.