Why Do People Become Infatuated With Someone Outside Their Relationship? Study Finds New Clues

A new study suggests that becoming intensely preoccupied with someone outside a committed relationship may reflect a mix of personality traits, sexual attitudes and dissatisfaction within the primary relationship. The findings indicate that both traditionally “dark” and more prosocial personality characteristics can be associated with extradyadic infatuation, although not always in expected ways.

Published in Psychological Reports, the study focused on extradyadic infatuation, defined as a cognitive, emotional and motivational preoccupation with another person while someone remains in a primary romantic relationship. Importantly, the research examined internal thoughts and feelings rather than confirmed acts of sexual or romantic infidelity.

Personality traits behind outside infatuation

The researchers examined several personality frameworks that have previously been linked to mating behavior and relationship dynamics.

The Dark Triad includes Machiavellianism, narcissism and psychopathy. These traits are generally associated with characteristics such as manipulation, entitlement, callousness and reduced empathy, although people vary considerably in how strongly they express them.

The researchers also examined the Light Triad, which includes Kantianism, humanism and faith in humanity. These traits are intended to capture more prosocial orientations, such as valuing other people as individuals, recognizing their dignity and holding generally positive beliefs about human nature.

Another factor was sociosexuality, which reflects how comfortable or willing a person is to engage in sexual relationships without strong emotional commitment. Previous research has linked unrestricted sociosexuality with greater openness to short-term or nonexclusive sexual relationships.

How the study was conducted

The study included 303 adults in Romania between the ages of 19 and 64 who were currently in romantic relationships.

To participate, individuals also had to report attraction toward or liking someone they knew in real life other than their current partner. The sample therefore did not represent all partnered adults, but rather people who were already experiencing some degree of attraction outside their relationship.

Most participants were women, and many were married or involved in long-term relationships.

Participants completed questionnaires assessing Dark Triad and Light Triad personality traits, sociosexual orientation, relationship satisfaction and the intensity of their extradyadic infatuation.

Infatuation was assessed through participants’ thoughts, emotions and motivations toward the other person. The study did not require participants to have acted on those feelings, making it important to distinguish extradyadic infatuation from behavioral infidelity.

Dark and light traits both showed associations

Initial analyses suggested relatively straightforward patterns. Stronger Light Triad characteristics were associated with lower levels of extradyadic infatuation, while Dark Triad traits, greater sociosexuality and lower relationship satisfaction were associated with stronger infatuation.

However, the pattern became more complicated when the researchers examined all variables simultaneously.

In the final statistical model, psychopathy, sociosexuality and lower satisfaction with the primary relationship remained associated with stronger extradyadic infatuation.

This suggests that people who scored higher on psychopathy-related characteristics, were more open to uncommitted sexual relationships and felt less satisfied with their current relationship tended to report stronger preoccupation with an alternative partner.

These findings are correlational, however. The study cannot determine whether these characteristics increase the likelihood of infatuation, whether becoming infatuated affects how people evaluate their relationship, or whether other factors influence both.

Faith in humanity also played a role

Lower faith in humanity was associated with greater extradyadic infatuation in the multivariable analysis.

Faith in humanity reflects a general tendency to view other people as fundamentally good and trustworthy. The finding suggests that people with a more cynical or distrustful outlook may also report stronger attraction or preoccupation outside their primary relationship.

However, the study does not establish why this association occurs. It would therefore be speculative to conclude that cynicism directly weakens commitment or causes people to invest more heavily in alternative partners.

Unexpected findings for humanism and Machiavellianism

Two results were particularly counterintuitive.

Humanism, a Light Triad trait involving valuing the dignity and worth of other people, initially appeared to be associated with lower extradyadic infatuation. But after other variables were controlled statistically, higher humanism was associated with stronger infatuation.

The researchers discussed the possibility that people higher in humanism may be especially open to emotional connection with others, which could in some circumstances make strong attachments outside a primary relationship more likely.

That explanation remains tentative. The statistical association does not demonstrate that empathy, emotional sensitivity or concern for others causes extradyadic attraction.

Machiavellianism showed the opposite reversal. Although it was initially associated with greater infatuation, it became a negative predictor after other variables were included in the model.

The authors suggested that people higher in Machiavellianism may be less inclined toward the emotional investment involved in intense infatuation and may instead approach relationships more strategically or instrumentally.

Again, this represents a possible interpretation rather than a mechanism demonstrated directly by the study.

Not all dark or prosocial traits behaved alike

Narcissism and Kantianism were not significant predictors of extradyadic infatuation once the other variables were considered.

This indicates that broad labels such as “dark” or “light” personality may conceal important differences between individual traits.

Lead author Teodora-Elena Huțanu emphasized that the findings complicate the idea that attraction outside a relationship is confined to people with obviously antisocial or selfish characteristics.

The study instead suggests that extradyadic infatuation may emerge from a combination of personality, sexual attitudes and relationship context.

At the same time, experiencing attraction or infatuation outside a relationship is not equivalent to committing infidelity. The study focused on internal experiences and did not establish whether participants crossed the boundaries of their relationships.

Important limitations of the findings

The researchers noted several limitations.

The sample was predominantly female, which may limit how well the findings apply to men or more gender-balanced populations. Because all participants were recruited in Romania, cultural expectations surrounding relationships, fidelity and attraction may also have influenced the results.

The study further relied entirely on self-reported information. Participants’ descriptions of their personality, relationship satisfaction and feelings toward another person may be influenced by memory, interpretation or social desirability.

Another limitation is that the researchers did not distinguish clearly between monogamous and consensually non-monogamous relationship arrangements.

That distinction matters because attraction to another person may have very different meanings depending on the rules and expectations established within a particular relationship. Feelings that represent a boundary concern in one relationship may be accepted or explicitly permitted in another.

The cross-sectional design also prevents conclusions about cause and effect. All measures were collected at approximately the same point in time, so the researchers could not determine whether personality traits and relationship dissatisfaction preceded infatuation.

What future research could reveal

Longitudinal research could help clarify how extradyadic attraction develops and changes over time.

Future studies could examine whether particular personality characteristics, sociosexual attitudes or relationship difficulties predict later increases in infatuation, and whether intense outside attraction subsequently affects satisfaction or commitment to the primary relationship.

Huțanu also plans to investigate whether extradyadic thoughts and emotions eventually translate into behavioral infidelity or longer-term relationships with the outside person.

Research that includes both partners, distinguishes different relationship structures and follows people over time could provide a more complete picture of how attraction outside a committed relationship develops.

For now, the findings suggest that extradyadic infatuation cannot be reduced to a simple contrast between “good” and “bad” personality traits. It appears to reflect a more complicated combination of individual differences, sexual attitudes and relationship circumstances.

Article prepared by Victoria Caldwell.