Infidelity has no single cause. In a study of 495 people who self-reported infidelity, Selterman and colleagues (2019, Journal of Sex Research) identified at least nine categories of motives: dissatisfaction with the relationship, neglect, anger at the partner, sexual desire, lack of love, low commitment, esteem (wanting to feel more popular or seen), wanting sexual variety, and situational factors. A machine-learning study of 1,295 people (Vowels et al., 2022) found the strongest predictors were relational: relationship satisfaction, love, desire and relationship length.
Does Infidelity Always Come From an Unhappy Relationship?
For a long time, the working assumption was that an affair grows out of a deficit — something missing at home. Earlier research on motives mostly recorded four: dissatisfaction, neglect, anger at the partner and sexual desire.
A 2019 internet questionnaire study by Selterman, Garcia and Tsapelas, mostly of young adults, found five further motives: “I had fallen out of love with my partner”, “I was not very committed”, “I wanted to enhance my popularity”, “I wanted a greater variety of sexual partners”, and situational reasons that had little to do with the partner.
Personality appeared in the picture too. Attachment insecurity was associated with anger, lack of love, neglect, low commitment and esteem motives — the wish to feel admired. An unrestricted sociosexual orientation, meaning comfort with sex without commitment, was associated with the sexual-variety motive.
Quotable: Infidelity is not one behaviour with one cause, but a set of behaviours driven by distinct motives, from anger and neglect to desire, esteem and situation (Selterman et al., 2019).
These findings align with a multi-factor view that later research supports: motives overlap, and one affair can carry more than one meaning. The limits are real — self-reports after the fact, cross-sectional questionnaires, mostly young online samples — and cannot be generalised to every age or culture.
Sometimes the body is in the embrace while the mind is elsewhere; research lists lack of love and low commitment among reported motives for infidelity — Image: AI-generated / Gemini 3.1 Flash via OpenRouter
Does the Reason for an Affair Change What Happens Next?
Yes, according to Selterman and colleagues (2021, Journal of Sex & Marital Therapy), who studied 495 U.S. undergraduates and internet participants. Dyadic motives — anger at the partner, lack of love — were linked with longer affairs, more public dates with the affair partner, and dissolution of the primary relationship.
Situational motives, such as feeling stressed, told a different story: shorter affairs, less satisfying sex during the affair, and lower rates of disclosure and dissolution. The reason behind an affair carried information about how it unfolded and how the couple fared afterwards.
Quotable: The motive behind an affair predicts its course: affairs rooted in the relationship ran longer, were more public, and more often ended the primary relationship, while situational affairs were shorter and less often disclosed (Selterman et al., 2021).
In practice, asking “why” is not about blame, it shows what needs repair. This fits the multi-motive picture from 2019, where motive is a signal rather than a verdict. These accounts were retrospective and self-reported, so they show associations, not causes.
Can Infidelity Be Predicted?
Vowels, Vowels and Mark (2022, Journal of Sex Research) used machine learning — random forest models interpreted with Shapley values — in two studies, one individual and one dyadic, with 1,295 participants and both in-person and online infidelity. Infidelity was, in their words, “somewhat predictable”. The most important predictors were interpersonal: relationship satisfaction, love, desire and relationship length. The authors suggest that addressing relationship difficulties early may help prevent infidelity.
“Somewhat” is the key word. These models describe group-level tendencies: they explain what raises risk across many people, not whether one person will stray. Treating a partner as a probability is neither accurate nor fair.
Quotable: Infidelity is not random, but it is not determined either; the variables that matter most — satisfaction, love, desire and relationship length — are relational (Vowels et al., 2022).
Clinicians working with Iranian couples in Tehran, Toronto and Los Angeles often observe that affairs rarely happen overnight. They tend to follow a long period of unspoken needs, unacknowledged desire and quiet emotional distance.
What Does Psychoanalysis Say About Infidelity?
Freud’s 1912 paper, “On the Universal Tendency to Debasement in the Sphere of Love”, described the affectionate and the sensual currents of love. In some people — particularly the men he wrote about — they fail to converge: where they love, they do not desire.
This speaks to the desire and sexual-variety motives. An affair does not always mean love has ended; sometimes it reveals a split between the person we love and a desire we dare not voice there. Psychoanalytic work puts that split into words rather than judging it.
For Iranian couples, at home or abroad, talking about desire is still shaped by shame, and that silence creates space for the unspoken to be sought elsewhere.
When to seek help: if a relationship is drifting toward distance or temptation, or if an affair has happened, speaking with a sexual health and couples specialist offers a safe space to understand “why” and decide “what now”.
No. In Selterman et al. (2019), lack of love was only one of nine motive categories, alongside anger, neglect, desire, esteem, low commitment, sexual variety and situational factors. In the 2021 follow-up, affairs driven by situational motives were less likely to end in a breakup.
What is the strongest predictor of infidelity?
In Vowels et al. (2022), the strongest predictors were relational: relationship satisfaction, love, desire and relationship length. The authors describe infidelity as only “somewhat predictable” — useful for understanding patterns, not for forecasting one person.
Does attachment style play a role?
Partly. Selterman et al. (2019) found that insecure attachment was associated with anger, lack of love, neglect, low commitment and esteem motives. This is correlation, not causation, and most people with an insecure attachment style never have an affair at all.
Can a relationship recover after an affair?
Many couples do repair the relationship after an affair. Motive matters: Selterman et al. (2021) found that situational motives were linked with lower rates of dissolution. Understanding why the affair happened, rather than only what happened, is usually the first step.
Conclusion
Infidelity has no single story. The reasons range from long-standing dissatisfaction to anger, desire, esteem and circumstance, and the same act can mean different things to different couples. The hopeful part is this: the strongest risk factors — satisfaction, love and desire — sit inside the couple’s own hands. Even after an affair, understanding its motive can be the beginning of a deeper, more honest relationship.
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Selterman D, Garcia JR, Tsapelas I. Motivations for Extradyadic Infidelity Revisited. J Sex Res. 2019;56(3):273-286. doi:10.1080/00224499.2017.1393494. PMID: 29244527
Selterman D, Garcia JR, Tsapelas I. What Do People Do, Say, and Feel When They Have Affairs? Associations between Extradyadic Infidelity Motives with Behavioral, Emotional, and Sexual Outcomes. J Sex Marital Ther. 2021;47(3):238-252. doi:10.1080/0092623X.2020.1856987. PMID: 33377428
Vowels LM, Vowels MJ, Mark KP. Is Infidelity Predictable? Using Explainable Machine Learning to Identify the Most Important Predictors of Infidelity. J Sex Res. 2022;59(2):224-237. doi:10.1080/00224499.2021.1967846. PMID: 34431739
Freud S. (1912). On the Universal Tendency to Debasement in the Sphere of Love (Contributions to the Psychology of Love II). In: The Standard Edition of the Complete Psychological Works of Sigmund Freud, Vol. 11, pp. 177–190. London: Hogarth Press.
Image Credits
Featured image and first in-text image: AI-generated / Gemini 3.1 Flash via OpenRouter. No real person is depicted.
