When it comes to the complexities of human relationships, new research suggests that our motivations for committed partnerships and casual encounters are more distinct than previously thought. A recent study published in Personality and Individual Differences challenges the long-standing idea that people’s relationship desires fall on a single spectrum, with casual sex on one end and long-term commitment on the other. Instead, the researchers found that these desires often coexist, suggesting that they are better understood as separate dimensions that independently influence our romantic behaviors and outcomes.
The motivation for this study stemmed from a growing recognition that traditional models of sociosexuality might be overly simplistic. Historically, researchers have often conceptualized sociosexuality as a single continuum, where a strong interest in casual sex (an unrestricted sociosexuality) indicates a weaker desire for committed relationships. However, this approach might be too reductive to capture the true diversity of human mating strategies.
Given the importance of long-term pair-bonded relationships in human life — contributing to happiness, health, and reproductive success — the researchers sought to explore whether a two-dimensional model could better explain how people navigate their romantic lives. They hypothesized that separating the motivations for casual sex and committed relationships into distinct dimensions could provide a clearer picture of how these motives impact relationship outcomes.
“For decades, the desire for casual sex and the desire for a long-term relationship have been treated as two ends of the same continuum. In other words, people either want to have casual sex or they want a committed relationship,” explained study author Sierra D. Peters, a doctoral candidate in social psychology at Florida State University.
“However, there are reasons to believe that greater motivation toward uncommitted sex may not necessarily reflect less motivation toward a committed relationship (and vice versa). By conflating these two important, and potentially distinct motivations, it’s possible that we are also obscuring important relationships between mating motives and people’s experiences in their relationships. Thus, we were interested in whether these two moves are associated with different relationship outcomes, and whether considering them separately helps us understand relationship outcomes better than lumping them together.”
To test their hypothesis, the researchers recruited 693 participants through Amazon’s Mechanical Turk, a popular online platform for gathering research data. After applying strict criteria to ensure that participants were paying attention and were in a romantic relationship, the final sample included 320 individuals. These participants were diverse in terms of age, gender, and race, with the majority identifying as heterosexual and being in monogamous relationships.
The researchers used two distinct tools to measure sociosexuality. The first was a traditional, one-dimensional measure, the Sociosexual Orientation Inventory, which assesses sociosexuality on a single continuum. This measure includes questions about participants’ past sexual behavior, future sexual intentions, and attitudes toward casual sex.
The second tool was a revised, two-dimensional measure, which separately assessed participants’ desire for casual sex and their desire for long-term pair bonding. This revised measure included subscales that specifically addressed each dimension.
For instance, the casual sex subscale included items that measured comfort and enjoyment in engaging in casual sex with different partners, while the pair-bonding subscale included items that measured the desire for a romantic relationship that lasts forever. These measures allowed the researchers to evaluate how each of these motivations independently influenced participants’ relationship behaviors and attitudes.
To assess the outcomes related to participants’ romantic relationships, the researchers employed the Investment Model Scale. This scale measures four key aspects of relationship quality: satisfaction, commitment, investment, and the perceived quality of alternative partners.
Satisfaction refers to the degree of positive feelings and attraction participants have toward their current relationship. Commitment reflects how strongly participants are dedicated to maintaining their relationship. Investment measures the resources, both tangible and intangible, that participants have put into their relationship, such as time and shared experiences. Finally, the perceived quality of alternatives assesses how appealing other potential partners are in comparison to the participant’s current partner.
The researchers found that when sociosexuality was measured using the two-dimensional model, it explained more variance in key relationship outcomes than when using the one-dimensional model.
For instance, people who scored high on the pair-bonding dimension reported greater satisfaction and commitment in their relationships. This suggests that a strong desire for a committed relationship correlates with more positive feelings and behaviors within the relationship. On the other hand, those who scored high on the casual sex dimension were less committed to their current partners and more interested in potential alternative partners, indicating that a strong motivation for casual sex may be linked to behaviors that could threaten the stability of long-term relationships.
Interestingly, the researchers also found that these two dimensions — casual sex and pair bonding — were only moderately inversely correlated. This means that a strong desire for casual sex does not necessarily preclude a strong desire for a committed relationship. In other words, it’s possible for individuals to simultaneously hold both desires, which challenges the traditional view that these motivations exist on opposite ends of a single spectrum.
“People frequently experience the desire for sex and the desire for a committed relationship simultaneously; such motives are not mutually exclusive. Moreover, these two motives predict relationship outcomes in different ways. Being motivated to form and maintain a long-term relationship is associated with greater satisfaction with, commitment to, and investment in one’s relationship as well as less interest in pursuing alternative partners.”
“In contrast, being motivated to pursue sex does not predict one’s satisfaction with or investment in their relationship, but it does predict less relationship commitment and greater interest in pursuing alternative partners. Importantly, these distinct relationships are only visible when you consider these mating motives separately.”
Despite its groundbreaking findings, the study is not without its limitations. One major limitation is that it relied on self-report measures, which can be influenced by social desirability bias — people may not always be truthful about their motivations for sex and relationships, especially when these motives conflict with societal norms. Additionally, the study’s cross-sectional design means that it provides only a snapshot in time, making it difficult to determine causal relationships.
The study’s focus on long-term relationship outcomes leaves open many questions about how these two dimensions of sociosexuality might influence other aspects of human mating behavior, such as initial attraction or mate selection. Researchers could also explore how these motivations interact over time.
“In the future, we are interested in examining how these two motives may interact to predict relationship outcomes. For example, given that sexual motives are associated with greater interest in alternative partners while long-term relationship (i.e., pair bonding) motives are associated with less interest in alternatives, what happens when people have both strong sexual and strong pair bonding motives? How does the interaction of these two competing motivations predict their thoughts, feelings, and behaviors toward alternative partners?”
The study, “Distinct individual differences in motivations for pair-bonding and sexual behavior: Implications for close relationships,” was authored by Jaia N. Hendrickson, Sierra D. Peters, Juliana E. French, and Jon K. Maner.
