The Science of Infidelity: Why Do People Cheat On Their Partners?

Love is undoubtedly one of the purest emotions that human being can experience; the world simply wouldn’t be as beautiful if it weren’t for love. There are many forms and manifestations of love that arise in different situations and scenarios, but in this article, we are going to talk about ‘romantic’ love, namely the loving relationships shared by partners and spouses.

Credit: Voyagerix/Shutterstock

Credit: Voyagerix/Shutterstock

Trust forms the foundation of any romantic relationship; if trust is lost, an ever-lasting relationship seems close to impossible. However, this is no secret; everyone knows this about love and trust, yet we see trust being compromised all the time in relationships. Why do some people tend to cheat on their partners and spouses, whom they claim to “love”? Is there a scientific explanation behind this?

Infidelity (AKA: Cheating)

Approximately 3% of all mammals in the world are monogamous, which is rather low in comparison to other animal groups, such as birds (roughly 90% monogamy rate). Monogamy, for those unfamiliar with the term, means staying with one partner for one’s entire life. Humans fall in this category of mammals, and this is not without its reasons. There is an evolutionary basis to monogamy.

Throughout evolutionary history, two partners staying together for their entire life meant that one partner could go out looking for food and resources, while the other could provide nourishment to their young. Despite the obvious benefits of such a loyal lifestyle, extra-pair mating, more commonly known as cheating, is fairly common.

The Role of Dopamine Receptors in Infidelity

credits: Zerbor/Shutterstock

credits: Zerbor/Shutterstock

If you would take a comprehensive scientific look at human happiness and feelings of pleasure, you would quickly come across the word ‘dopamine’, which is a powerful hormone in the body. The genetic coding of dopamine receptors plays an important role in a person’s loyalties. Dopamine, also referred to as the ‘happy hormone’, is a neurotransmitter that is released after (or during) certain pleasurable activities, including exercising, eating food, having sex etc.

It has been found that people who possess a long-alleled variant of dopamine receptor are 50% more likely to cheat on their partners than individuals with the short-alleled variant, who happen to cheat about 20% of the time. People with long-allele variant are also more likely to indulge in thrill-seeking and addictive behaviors.

Levels of Vasopressin

baby cuddle

A hormone called vasopressin also plays an important role. This hormone is pretty similar to oxytocin (sometimes referred to as the ‘cuddle hormone’), which influences feelings of trust, affection and empathy. Thus, a person with higher vasopressin levels is more likely to be more loyal.

Money Matters!

Credit: wavebreakmedia/Shutterstock

Credit: wavebreakmedia/Shutterstock

Many would not find money to be much of a scientific reason behind infidelity, but it is a very common reason behind people cheating on their partners. It has been observed that men who earn far more money than their wives are more likely to cheat. Although this is not true in every case, the chances of infidelity drop significantly when the earnings of both partners is similar.

These are not the only reasons that lead people to cheat; in practice, it would be impossible to list down all the feasible reasons of why a person cheats on their partner. Still, the reasons that surface rather commonly in cases of infidelity include issues from past relationships, excessive alcohol use (or other forms of intoxication), and unresolved emotional issues are also very common reasons behind infidelity.

cheating meme

This shows that biology does play an important role in your loyalty levels, but it doesn’t mean that you have no control over your own actions. The famous quote of Bruce Wayne from Batman sums this idea up quite nicely: ‘It’s not who you are underneath, but what you do that defines you.’


  1. Psychological & Brain Sciences UC Santa Barbara
  2. Increases Infidelity Among Men and Women – Leeds Faculty Colorado
  3. The Biology Of Cheating Spouses – Medical Daily
  4. Ideas Ted
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Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

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