Study on Serial Infidelity – What “Once a Cheater, Always a Cheater” Really Means

The phrase “once a cheater, always a cheater” is often used in conversations about relationships, usually as a warning after betrayal. While the statement may sound overly simplistic, psychological research suggests there may be some truth behind it. A study involving more than 400 adults found that people who cheated in one relationship were significantly more likely to repeat the behavior in future relationships.

At the same time, researchers caution against treating infidelity as an unavoidable pattern. The findings point to statistical tendencies, not guaranteed outcomes. Human relationships remain complex, shaped by communication, trust, emotional health, and personal growth.

Research

In 2017, clinical psychologists at the University of Denver conducted a study examining whether infidelity in one relationship could predict cheating in later relationships.

The research followed 484 English-speaking young adults in the United States over time. Participants completed detailed questionnaires about their romantic experiences, including cheating, suspicions of infidelity, and relationship dynamics.

The goal was to understand whether certain relationship behaviors repeated themselves across different partnerships.

The findings suggested that past relationship experiences often influence future behavior.

Findings

Researchers discovered that individuals who admitted cheating in a previous relationship were about three times more likely to cheat again in a later relationship.

The study also found that people who had previously been cheated on, or suspected a partner of cheating, were two to four times more likely to experience similar situations again.

Lead researcher Kayla Knopp explained that relationship history often shapes future romantic patterns.

“The past matters for relationships,” Knopp said while discussing the findings. According to the researchers, behaviors and experiences from earlier relationships frequently carry over into future ones.

Patterns

Psychologists often study relationships through the lens of behavioral patterns. Habits, coping mechanisms, communication styles, and attachment behaviors can become repeated over time unless individuals actively work to change them.

In the case of infidelity, repeated behavior may reflect unresolved emotional issues, impulsivity, difficulty with commitment, or unhealthy relationship dynamics.

However, the study did not suggest that people are permanently defined by their past mistakes. Instead, it highlighted that previous actions can sometimes predict future risks.

This distinction is important because statistical probability does not equal certainty.

Gender

One notable finding from the research was that infidelity rates appeared relatively equal between men and women.

The study found no major gender difference in either cheating or being cheated on. This challenges older stereotypes that often framed infidelity as more common among one gender.

Researchers also reported that approximately 40 percent of unmarried couples in the study experienced some form of infidelity.

That figure reflects how common trust-related issues can be in modern relationships, particularly among younger adults navigating long-term commitment.

Psychology

Psychologists say repeated relationship experiences can sometimes be linked to attachment styles and emotional behavior developed earlier in life.

For example, individuals with insecure attachment patterns may struggle with trust, emotional closeness, or communication. These difficulties can influence how they behave in future relationships.

Likewise, people who have experienced betrayal may become more anxious, suspicious, or emotionally guarded in later partnerships. In some cases, those fears can unintentionally contribute to unhealthy relationship dynamics.

The researchers emphasized that this does not mean victims are responsible for being cheated on. Instead, it suggests that both partners influence relationship outcomes through communication patterns, emotional responses, and personal boundaries.

Context

Although the findings attracted attention because of the phrase “once a cheater, always a cheater,” the researchers themselves presented the results carefully.

They stressed that the study identified trends rather than fixed rules. Many people who cheat once never repeat the behavior, while others learn from past mistakes and develop healthier relationships over time.

Similarly, people who have experienced betrayal are not destined to face repeated infidelity forever.

Knopp noted that many individuals successfully break these cycles through self-awareness, personal growth, and healthier relationship choices.

Relationships

Experts say recognizing relationship patterns can help people make more informed decisions.

Knowing past behaviors may encourage individuals to pay closer attention to trust, communication, emotional compatibility, and conflict resolution in future relationships.

Some therapists also recommend reflecting on recurring relationship experiences instead of viewing them as isolated incidents. Identifying repeated patterns can help people establish healthier boundaries and improve emotional awareness.

At the same time, psychologists warn against reducing people to a single label based on past behavior alone. Relationships are influenced by many factors, including maturity, environment, emotional health, and life circumstances.

Trust

Trust remains one of the most important foundations of long-term relationships. Once trust is broken, rebuilding it often requires honesty, accountability, consistency, and emotional transparency from both partners.

Research on infidelity continues to show that betrayal can have lasting emotional effects, including anxiety, insecurity, and difficulty trusting future partners. However, many couples are also able to recover through communication and professional support.

The University of Denver study ultimately reinforces a broader psychological principle: past experiences often shape future behavior, but they do not completely determine it.

Patterns may increase risk, but individuals still have the ability to change, learn, and build healthier relationships over time.

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