Do you prefer casual sex or serious relationships?
Current research would have us believe that our drive for intimacy only pulls us in one of these directions. What’s more, stereotypes cast men as wanting to play the field while women pursue long-term love.
But what if these desires operate independently, allowing someone to seek commitment without ruling out short-term flings—or vice versa? And what if gender plays a less significant role than we think?
A study in Personality and Individual Differences explores whether assessing personal motivations for sex and pair-bonding separately, rather than as two ends of the same spectrum, can better predict relationship outcomes. This method could advance research toward a richer, more nuanced understanding of human relationships.
A tale of two motivations
It’s common to approach the study of casual sex and committed partnerships from a one-dimensional perspective. Yet, several theories suggest that our motivations for these types of relationships stem from two distinct systems.
In 1998, renowned love expert and biological anthropologist Helen Fisher, Ph.D., proposed there’s one system for lust and another for attachment. Lust evolved to encourage sexual encounters with any suitable partner, while attachment developed to nurture long-term pair bonding. Each system functions through fundamentally different biological and behavioral mechanisms.
A 2007 study by Jackson and Kirkpatrick was the first to emphasize that people can pursue both long-term and short-term relationships simultaneously. Specifically, a strong drive for casual sex doesn’t exclude the possibility of also wanting a committed partner. This suggests that individuals can hold different attitudes toward various types of relationships.
Unpacking sociosexuality scales
Researchers studied 320 people in long-term relationships to examine if a one- or two-dimensional scale could more accurately capture relationship dynamics.
They compared two versions of the Sociosexual Orientation Inventory (SOI): the original, developed by Simpson and Gangestad in 1991, and a multi-dimensional update by Jackson and Kirkpatrick in 2007.
The original SOI uses a single scale to measure sociosexuality, which reflects an individual’s openness to casual sex. Higher scores suggest a stronger interest in short-term flings, while lower scores indicate a preference for committed relationships.
In contrast, the revised SOI gauges these motivations with two scales: short-term mating orientation (STMO) and long-term mating orientation (LTMO).
Through surveys, researchers also assessed participants’ levels of relationship satisfaction, relationship investment, relationship commitment, and interest in attractive relationship alternatives. They hypothesized that the two-part measure would provide a more detailed understanding of these factors.
Participants had an average age of 35 and were racially diverse: 63% identified as White, 18% as Black, 12% as Asian, 4% as Latino, and 3% as American Indian or another group. The majority (76%) identified as straight, with 4% identifying as gay or lesbian and 20% as bisexual. They had an average relationship length of 7 years, and about 90% were monogamous.
Comparing measures
Two scales are better than one!
The revised SOI did a better job of explaining why people have different levels of relationship satisfaction, commitment, investment, and interest in other potential partners.
In addition, the study found that long-term mating and short-term mating orientations are only somewhat related, suggesting they are in fact different concepts.
Relationship satisfaction
The original SOI could not reliably predict relationship satisfaction, statistical analysis revealed.
Yet the revised SOI predicted 6% of scores. People with higher long-term mating orientation scores reported greater relationship satisfaction, while higher short-term mating orientation scores had no effect—even when considering sex.
Relationship commitment
While the original SOI explained only 15% of relationship commitment scores, together the LTMO and STMO explained 65%.
Sex influenced commitment in the original SOI, with women showing more commitment than men. However, it had no effect on long-term mating orientation and short-term mating orientation. Overall, people focused on long-term relationships were more committed, while those focused on short-term ones were less committed.
Relationship investment
When it came to predicting relationship investment, the STMO and LTMO scales did a much better job, explaining 27% of scores. The original SOI explained about 2%. Gender showed no significant impact.
People with higher SOI scores, indicating greater interest in casual sex, tended to be less invested in their relationships. Yet those with higher short-term mating orientation scores showed no difference in relationship investment. As for people with higher long-term mating orientation scores, they were more invested in their current relationships.
Interest in other partners
How tempted are people to stray?
In general, people focused on long-term relationships showed less interest in other partners. On the other hand, those after short-term flings were more likely to have wandering eyes.
Regarding gender, the original SOI found men were more drawn to attractive alternatives. But when it came to LTMO and STMO scores, sex made no difference.
The SOI explained 28% of people’s interest in other partners, while STMO and LTMO scores explained 54%.
Chasing both love and lust
Are we wired for both flings and long-term love?
Results suggest casual sex and committed relationships aren’t mutually exclusive. People can be driven by both, and separating these motivations—casual (STMO) and long-term (LTMO)—gave a clearer picture of relationship behaviors.
What truly drives relationship preference also appears to be less about biological sex and more about personal motivations. For instance, gender differences shown in the single-scale SOI vanished when considering both sexual and pair-bonding motives.
Notably, people who wanted casual sex showed more interest in attractive alternatives, regardless of their desire for a strong bond. If we only viewed these motivations on a continuum, we’d overlook the power of different desires to shape our feelings and actions.
Future studies could dig deeper by exploring how mating motives evolve and impact relationships over time. In addition to using implicit measures over self-reporting, research stands to benefit from unpacking the influence of hormones such as testosterone and oxytocin.
In the quest for love and lust, the depths of human desires may be a lot more nuanced than we imagined.
