Why "Happy" People Cheat: A Look Inside the Psychology of Infidelity

Imagine if infidelity were a crime. You cheat, you get caught, and both you and your lover face a real prison sentence. One might think the fear of jail would deter even the smallest inclination towards cheating. A potential lover would think twice before getting involved with a married person, and that person would surely weigh the risk of years behind bars against a fleeting affair.

This isn't just a thought experiment. In the Philippines, a country of over 115 million people, marital infidelity is a criminal offense. The law is enforced, with penalties of up to six years in prison. And yet, what do anonymous surveys reveal? No significant decrease in the number of infidelities compared to countries without such laws. Even under the threat of prison, people still cheat.

This paradox reveals a deeper truth: our understanding of infidelity is far more complex than any law can define. In the Philippines, the law is concerned only with sexualized contact. Romantic letters, gifts of flowers, secret dates—none of these legally constitute infidelity. But we know, in the landscape of a relationship, betrayal is a much broader concept. So, what actions do we truly consider to be cheating?

The Elusive Definition of Betrayal

If you had to define infidelity, could you? There is no universal consensus. Is a woman cheating if she hugs another man and feels a spark of sexual attraction? Is a man unfaithful for wanting to send flowers to a colleague he admires? What about exchanging intimate photos with someone miles away, or grinding on a dance floor while intoxicated, only to regret it the next day? Where do we draw the line between an attempt at infidelity and the act itself?

This ambiguity creates a major problem when we try to understand human behavior. Studies often report a startling figure: in roughly 70% of marriages, at one point or another, one of the partners has been unfaithful. For men, the figure is sometimes cited as closer to 80%; for women, around 60%—though this gap may reflect societal pressures on women to underreport more than an actual difference in behavior.

But what does this 70% figure truly mean? It's a number shrouded in mystery. One person in that sample might check "yes" because they had a full-blown affair. Another might check "yes" remembering a flirtatious dance from 15 years ago. Conversely, someone who has regular, emotionless sex with a neighbor might check "no" because they don't feel it's cheating. They are all part of the same statistic, rendering the number both powerful and frustratingly vague. We know the prevalence is high, but we can't be sure what behavior it actually describes.

A Tale of Two Perspectives

To shed light on this, researchers have tried to pinpoint what people actually consider infidelity. The results often depend entirely on who you ask.

The View from Inside

A fascinating 2020 study from the University of Maryland zoomed in on a specific group: people in long-term relationships who had regularly cheated on their partners with different people over the previous five years. Let's call them "RPIs" (Regularly Practicing Infidelity). When asked what acts they considered infidelity, their answers were starkly clear.

• Kissing: Around 87% for both men and women considered this cheating.
• Mutual Masturbation: Over 60% of men and 46% of women.
• Oral & Vaginal Sex: Roughly half of the respondents engaged in and counted these acts.
• Absence of Sexual Contact: Only a tiny fraction considered non-sexual acts—like texting, emotional infatuation, or sending intimate photos—to be infidelity.

For this group, the line was drawn almost exclusively at physical, sexualized contact. What's more, a surprising 56% of them reported being in happy marriages. They weren't cheating out of revenge, unhappiness, or dissatisfaction with their partner. Their reasons were disconnected from the state of their primary relationship. This implies their spouses were either unaware or, perhaps, knew and were simply okay with it.

The View from the Outside

But what about the general population? A separate, broad survey published in March 2024 gives a much different picture. When a cross-section of society was asked what they consider infidelity, the definitions became much broader and more emotional.

• Sexual Intimacy: Nearly 100% agreed this was infidelity.
• Hugs and Kisses: About 75% considered this cheating.
• Romantic Correspondence/Sexting: About 40% saw this as a betrayal, while 60% did not.
• Sexual Attraction to Another Person: This split the crowd right down the middle—50/50.
• Going on a Romantic Date: Also a 50/50 split.
• Developing Romantic Feelings: 40% considered this infidelity.
• Flirting: Roughly 40% saw this as cheating, meaning a majority were comfortable with their partner flirting.

These two perspectives show the deep divide in our collective understanding. What one person dismisses as harmless, another sees as a profound betrayal.

Navigating Fidelity in the Real World

Given this landscape of ambiguity and high stakes, how can we approach fidelity in our own lives? As a psychologist, I see the fallout from these mismatched expectations daily. Here are a few practical considerations.

1. Acknowledge the Complexity, Not the Ideal

   The data is clear: in seven out of ten long-term relationships, some form of infidelity has likely occurred. And for the other 30%, we can't be sure what their "no" even means. It’s also been observed that as people age, their attitude toward infidelity often softens. Perhaps this isn't cynicism, but a sign of maturity—an understanding that life is messy and humans are imperfect. Idealizing your marriage as an impenetrable fortress against temptation is setting it up for a painful fall.

2. Define Your Own Terms

   If you desire a monogamous relationship, the most critical conversation you can have is not about a blanket ban on cheating, but about defining what infidelity means to you both. As the studies show, society offers no clear rules. You must create your own. Is flirting with a coworker over the line? Is watching pornography a betrayal? Is an emotional connection with an old flame considered cheating? Hash it out. An agreement on the definition is far more powerful than a simple promise to be "faithful."

3. The Burden of Confession

   This may be controversial, but never confess to infidelity. Even if you are caught, deny it. While honesty is a virtue, a confession often serves the cheater’s need to assuage guilt more than it helps the betrayed partner. It simply transfers the pain, creating a trauma that may never heal. Even in relationships where there’s a tacit understanding—"do what you want, just don't tell me"—the confirmation is still a blow. Infidelity is a personal failing that you must work through on your own. Your partner will likely sense the shift in your behavior, but the burden of a confession can shatter a relationship beyond repair. Don’t cooperate with the investigation.

Ultimately, finding harmony in a partnership is about reaching a mutual understanding on this deeply personal issue. I wish you all the best in finding that agreement.

References

• Selterman, D., Garcia, J. R., & Tsapelas, I. (2019). What constitutes cheating? An update on contemporary folk conceptualizations of infidelity-related behaviors. The Journal of Sex Research, 56(6), 685-699.

  This study directly explores the central theme of the article: the lack of a universal definition of cheating. Researchers surveyed hundreds of people on whether they considered various behaviors (from sexual acts to emotional and online activities) to be infidelity. Its findings support the idea that perceptions of betrayal exist on a spectrum, confirming the ambiguity discussed in the article.

• Glass, S. P., & Wright, T. L. (1992). Justifications for extramarital relationships: The association between attitudes, behaviors, and gender. Sex Roles, 26(5-6), 221-236.

  This classic paper provides evidence for the surprising finding that people in happy marriages still engage in infidelity. It examines how individuals justify their affairs and finds that marital dissatisfaction is not the only, or even primary, driver. This aligns with the article's discussion of the "RPI" sample, where 56% of those who regularly cheated reported being in happy relationships.

• Mark, K. P., Janssen, E., & Milhausen, R. R. (2011). Infidelity in heterosexual couples: Demographic, interpersonal, and personality-related predictors of extradyadic sex. Archives of Sexual Behavior, 40(5), 971-982.

  This research provides robust data on the prevalence of infidelity. While rates vary, the study reports that approximately 23% of men and 19% of women in their sample admitted to engaging in extradyadic sex. While lower than the 70% figure often cited in popular media, it confirms that infidelity is a significant phenomenon in a substantial portion of relationships and explores the factors that predict it.