The psychology of infidelity: Why do we cheat?

Infidelity, an inherently selfish behavior, has been analyzed by researchers to help us understand why people cheat in relationships.

unfaithful husband looking at phone while with mistress

What are the most common reasons for cheating in a relationship?

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  • Results of a 2005 study show that there is a significant difference between cheaters and non-cheaters when it comes to the Big Five model of personality traits.
  • Poor self control, selfishness, anger, boredom, and attention-seeking are the most common reasons a person is unfaithful in their relationship.
  • However, a 2018 study suggests that even infidelity, which is inherently a selfish behavior, is more than it seems - requiring an in-depth look at both the personality traits in each person in the relationship as well as the dynamic between them.

"The Big Five" personality trait model - a brief explanation

back of woman's head catching her husband cheating on her

What personality traits make a person more (or less) likely to cheat on a spouse?

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Defining the human psyche and explaining human behaviors has been a goal of psychologists and researchers for decades.

Pioneer psychologist Gordon Allport (1897–1967) once compiled a list of 4,500 different personality traits he believed explained the human condition. Raymond Cattel (1905–1998), a British-American psychologist best known for his research into intrapersonal psychology, later explained a shorter personality model with 16 different types of personality traits.

In the 1970s, we were presented with the model we know today as the Big Five. The Big Five was created by two independent research teams who took different approached to their studies of human behavior and arrived at the exact same result.

The first team was led by Paul Costa and Robert McCrae at the National Institutes of Health. The second was led by Warren Norman of University of Michigan and Lewis Goldberg of University of Oregon.

The Big Five (acronym OCEAN):

  • Openness to experience (a willingness to try new activities)
  • Conscientiousness (an awareness of your actions and the consequences of behavior)
  • Extroversion (outgoing, socially confident behaviors)
  • Agreeableness (cooperative, friendly and likable behaviors)
  • Neuroticism (anxious, over-thinking, worrying behaviors)

In 1998, Oliver John of Berkeley Personality Lab and Veronica Benet-Martinez of UC, Davis created what is known as the "Big Five Inventory" - a 44 item questionnaire that measures a person based on the Big Five factors and then divides those factors into personality facets.

These factors are measured on a spectrum - a person may be highly extroverted or highly introverted, or somewhere in between. You can see a copy of the Big Five Inventory here.

How does our personality affect our likelihood of cheating in a relationship?

In 2005, researchers Tricia Orzeck and Esther Lung conducted a study where participants voluntarily answered a questionnaire on personality traits about themselves and their monogamous partners. A total of 45 males and 59 females rated themselves and their partners (with a total of 208 people being involved in the study).

The results of this study proved that there is a significant difference between cheaters and non-cheaters when it comes to the Big Five model of personality traits.

This was further explained by a study in 2018, where data from two separate studies looked at the personality traits and relationship dynamics of new married couples. Both studies lasted 3 years in length and examined the associations between personality and infidelity.

Results of this study showed these were the couples who were most likely to experience infidelity in their marriage:

  • Wives who had high (compared to low) extroversion traits were more likely to be unfaithful.
  • Wives who were partnered with a husband who had high (versus low) neuroticism and/or extroversion traits were more likely to be unfaithful.
  • Husbands who were partnered with a wife who had high (versus low) neuroticism and/or extroversion traits were more likely to be unfaithful.
  • Husbands who were partnered with a wife who had high (versus low) narcissism traits were more likely to be unfaithful.

The results of this study suggest that one person's personality traits aren't enough to determine their likelihood of infidelity. Instead, infidelity requires an in-depth look at both the personality traits in each person in the relationship as well as the dynamic between them.

Why do we cheat?

According to a 2013 poll of 1535 American adults, having an affair is considered "more morally wrong" than gambling, human cloning, and medical testing on animals. And yet - so many people still experience heartbreak from infidelity in their relationships.

Psychotherapist and New York Times bestselling author Esther Perel wanted to understand why people cheat in relationships.

"Why do people do this? Why do people who have often been faithful for decades one day cross a line they never thought they would cross? What's at stake? How do we make sense of this and how do we grow from that?"

In her book "The State of Affairs: Rethinking Infidelity", Perel, who has worked with couples for 33 years, takes a look at infidelity not in an evidence-based scientific way, but from a sociological, anthropological angle.

While it's very common to have fantasies about being with someone other than your partner, not everyone who does this takes the step across that line to cheat on their partner. In fact, according to a 2001 study, 98% of men and 80% of women have admitted to fantasizing about someone other than their partner at least occasionally.

This is human nature, to be curious - but what makes a person go from naturally curious to morally ambiguous and cross the line to infidelity? While personality traits and the dynamic of your relationship play key roles, there is a lot of speculation on why people cheat.

Is technology to blame for "making cheating easier"?

Many people speculate that the surge in technology (dating apps and websites such as Ashley Madison, which targets married couples) may be one of the biggest reasons infidelity happens.

However, according to research conducted by Dr. Justin Lehmiller in 2015, the prevalence of cheating isn't any higher today than it was 20 years ago before the introduction of dating websites and apps.

Instead, psychologists have narrowed down some of the most common reasons people give for cheating on their spouses, which include:

  • Poor self-control or not feeling committed to the relationship: impulsive behaviors, not thinking about the consequences of your actions and lacking commitment to your current romantic partner.
  • Selfishness or anger: putting your needs above your partner's needs, not caring if your actions hurt those around you or wanting some form of "punishment" for your partner.
  • Attention-seeking: not feeling fulfilled in a current relationship, not having emotional or physical needs met.
  • Boredom and insecurity: feeling insecure about yourself, needing validation or wanting a "thrill," even if it comes from self-destructive behaviors such as cheating.

These motives vary from how you view yourself to how you view your relationship and the context of the situation at hand. When it comes to putting a label on infidelity, there is very rarely just one factor involved. It's never just about a person's personality traits, or the dynamic in the relationship - it's a combination of personality, events, and circumstance.

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