Betrayal. It’s not attraction to another person, nor is it mere dissatisfaction. What occurs most frequently is a more subtle inclination: the belief that an exception can be made for one’s own desire.
It’s nighttime. On a kitchen table, a phone screen lights up for a few seconds. An incomplete sentence appears—perhaps a name hidden behind an initial, certainly a time that would raise questions. In the next room, someone sleeps with the serenity of someone who believes they have their life figured out. The other person watches that light, deletes the message, and goes back to bed.
Perhaps the encounter hasn’t happened yet. Perhaps everything still lies in that ambiguous zone where every gesture can be downplayed: they’re just words, there’s been no contact, I can stop whenever I want. And yet the most important boundary may already have been crossed. Not at the moment of physical contact, but when one of the two decided that the shared rules could continue to apply to the couple without necessarily having to apply to themselves as well.
Science has not identified a universal profile of someone who cheats. There is no single trait capable of predicting such complex behavior with certainty, nor is there a single biological mechanism that can explain it. A systematic review published in 2019 by Arezoo Haseli and colleagues examined 82 quantitative studies, showing that infidelity is associated with a combination of individual, relational, social, and cultural factors.
Variables related to the relationship and the interaction between partners were, on the whole, more consistently associated with the phenomenon than many personal characteristics considered in isolation.
It is therefore not scientifically accurate to claim that everyone who is unfaithful possesses the same personality. However, if we examine the psychological processes that make it possible to violate a commitment, a specific disposition often emerges: a sense of entitlement, defined in Anglo-American literature as entitlement.
It is the tendency to believe that one’s own needs deserve special consideration, that frustration lessens responsibility, and that a subjective need can take precedence over the agreement established with the other person. This attitude does not necessarily coincide with narcissistic personality disorder. Labeling every unfaithful person a “narcissist” would be clinically inappropriate. A diagnosis requires specific criteria, a thorough evaluation, and problematic functioning that extends across multiple areas of life. It is, however, possible for a person—even without a pathological structure—to exhibit self-centered or self-indulgent behaviors in the emotional and sexual spheres.
In 2014, psychologists James K. McNulty and Laura Widman published two longitudinal studies conducted on a total of 123 newlywed couples. Their research examined so-called sexual narcissism, a construct comprising four components: exploitation of the partner, a grandiose perception of one’s own erotic abilities, a sense of sexual entitlement, and reduced empathy in that context.
Higher levels of the overall construct were associated with a greater likelihood of extramarital affairs, even when accounting for marital satisfaction, sexual fulfillment, and general narcissism. The authors did not claim that a single trait was present in every case; rather, they showed that the way a person conceives of their privileges in the erotic realm can be more informative than a generic personality label.
The crucial point, therefore, is not feeling attraction. It is the inner permission that allows one to transform it into secret behavior.
Before the act, a narrative often emerges that makes it tolerable: “Nothing is happening”; “After everything I’ve put up with, I deserve this”; “My partner doesn’t see me anymore”; “If they don’t find out, they won’t suffer”; “I’m entitled to something that makes me feel alive.”
These are different phrases, but they serve the same function: to reduce the conflict between the moral image the individual holds of themselves and the disloyalty of their actions. Acknowledging that we are deceiving someone who trusts us is psychologically more painful than reinterpreting the transgression as an inevitable consequence of a perceived shortcoming.
In a study published in 2018, Benjamin Warach, Lawrence Josephs, and Bernard S. Gorman used a statistical model to analyze the relationships between insecure attachment, sexual narcissism, primary psychopathy, previous experiences of betrayal, and self-exculpatory attributions.
Among the patterns that emerged, the justification of infidelity conceived as retaliation played a mediating role between certain psychological characteristics and extramarital behavior. The study does not prove that everyone follows the same trajectory, but it confirms the importance of self-justification in making acceptable what, viewed from the outside, would appear to contradict the commitments made.
Empathy, too, can remain present without being able to protect the relationship. Some fully understand that their partner would suffer; they are aware of their partner’s vulnerabilities and foresee the consequences of discovery. What is temporarily set aside is their emotional involvement in that pain.
The suffering of others is confined to an uncertain future: if their partner does not find out, it will not happen; if it does happen, it will be possible to deal with it later.
Thus, two parallel realities emerge. On one hand, there remains the home, the shared history, the habits, and the affections; on the other, a space opens up that is removed from mutuality, where different rules seem to apply. This separation makes it possible to be considerate in the morning and dishonest in the afternoon, to plan a vacation while shielding a clandestine conversation, to feel genuine affection and, at the same time, act in a deeply hurtful manner.
It is precisely this contradiction that disorients the person who discovers the deception. The most tormenting question becomes: Which of the two versions was true? The answer can be difficult to accept: in the mind of someone who had carefully divided the two worlds, both could appear sincere.
The quality of the bond matters. In 2022, Laura M. Vowels, Matthew J. Vowels, and Kristen P. Mark applied machine learning techniques to data from 1,295 participants. Among the most informative factors in predicting forms of infidelity—both online and in person—were relationship satisfaction, love, desire, and relationship duration. The results do not prove that a crisis inevitably leads to infidelity; rather, they indicate that couple dynamics carry significant weight and cannot be excluded from the analysis.
Dissatisfaction, however, does not eliminate individual responsibility. Two people may experience the same emotional distance and choose opposite paths. One confronts the conflict, asks for help, suggests therapy, sets a boundary, or ends the relationship. The other builds a hidden life. Suffering may explain vulnerability, but it does not make lying inevitable.
Those who intensely fear abandonment may seek confirmation of their own worth in the interest of a stranger. Those who feel uncomfortable with emotional dependence may use a parallel relationship to maintain a distance from deeper intimacy. In both cases, the third person risks becoming less a person encountered in their entirety and more a tool for regulation: they serve to quell the fear of not being enough, to avoid vulnerability, or to rediscover an idealized image of oneself.
Not even neuroscience justifies simplistic explanations. To say that people cheat “because of dopamine” is to reduce a complex decision to one of the systems involved in anticipation and reward. Novelty, desire, and social validation can activate motivational circuits, but such activation does not dictate behavior. Between impulse and action lie self-regulation, the ability to anticipate consequences, attention, internalized values, and the memory of the commitment made.
McNulty, Andrea Meltzer, Anastasia Makhanova, and Jon Maner followed 233 newlywed couples for about three years. Spouses who were able to shift their attention away from images of attractive alternatives more quickly were less likely to be unfaithful in the subsequent period. The authors did not describe a conscious form of repression, but rather partly automatic attentional and evaluative processes that are potentially useful for protecting the relationship.
From this perspective, fidelity does not equate to the absence of temptations: it also depends on how the mind avoids fueling them.
Then there’s the question that accompanies every precedent: If someone has cheated once, will they do it again? The scientifically correct answer is not “always,” but neither is it “it means nothing.” Kayla Knopp and her colleagues followed 484 adults through two successive relationships. Those who reported sexual involvement outside the relationship in their first relationship were about three times more likely to report it in the following one as well. This is a statistical increase in risk, not an irrevocable condemnation.
It may not only be the behavior that recurs, but also the psychological pattern that made it possible: undefined boundaries, a constant need for validation, low tolerance for frustration, a fascination with secrecy, or a habit of shifting the responsibility for one’s own decisions onto others. For this reason, genuine change is not simply a promise that it won’t happen again. It requires understanding why it happened, letting go of justifications, and learning to endure the discomfort of making a transparent choice.
For those who discover the infidelity, the experience does not merely alter their judgment of their partner. It can retroactively alter the meaning of their shared history. Trips, absences, messages, and memories are reexamined in search of what had gone unnoticed. The present hurts, but it is the past that suddenly becomes unstable.
A study by Lydia G. Roos, Victoria O’Connor, Amy Canevello, and Jeanette M. Bennett involved 73 unmarried young adults who had experienced a partner’s infidelity in the previous five years. 45.2 percent reported symptoms consistent with a probable post-traumatic condition related to the experience. The small sample size, the young average age of the participants, and the observational design do not allow this percentage to be generalized to the general population. However, the data show that, in some individuals, the discovery may be associated with clinically significant psychological consequences.
In terms of neuroimmunomodulation , it is essential to exercise the same caution. There is no specific biological marker for infidelity. Research does show, however, that relationship stress can affect endocrine, cardiovascular, and immune regulation. In a 2021 review, psychologist M. Rosie Shrout synthesized the main evidence on the psychobiological pathways through which relationship conflict can affect partners’ health.
A famous experiment by Janice Kiecolt-Glaser and colleagues, conducted on 42 married couples, compared the effects of a supportive conversation with those of a conflictual argument. After the hostile confrontation, small experimental skin lesions healed more slowly; in couples characterized by greater hostility, differences in the production of pro-inflammatory cytokines were also observed.
The study did not directly address infidelity, but it demonstrated concretely that the quality of intimate interactions can be accompanied by measurable biological changes.
The body, of course, does not react to an abstract term like “betrayal.” It responds to a loss of security, emotional hyperarousal, unpredictability, sleep disturbances, and a persistent state of alarm. Not every emotional wound leads to illness, but a relationship that has suddenly become unreliable can turn into a source of profound stress.
The most significant signs, then, are not always found on a phone.
They may appear much earlier, in the way someone conceives of reciprocity: strict rules for the other person and flexible boundaries for oneself; difficulty apologizing without adding a “but”; a constant need to be admired; a tendency to present every mistake as an inevitable reaction; a demand for absolute personal freedom accompanied by an expectation of unconditional loyalty.
The most revealing question is not whether a person might feel attracted to someone else. Attraction is part of the human experience and does not amount to a breach of the pact. The decisive question is what happens when one’s own desire conflicts with the dignity of the person who trusts you.
It is still night. The phone has been left on the table, and the screen is now dark. In the next room, someone is still sleeping. The person who deleted the message can still tell themselves that nothing happened, that silence will protect the couple, that everyone has the right to a secret part of their existence.
Yet that brief flash of light did not merely illuminate a clandestine phrase. It revealed, for an instant, the conviction from which many acts of infidelity take shape: the belief that one can demand loyalty from the other while granting oneself an exception.
