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What Makes People Jealous?

Being cheated on before, insecurity, and more.

Key points

  • Jealousy occurs when one’s romantic partner is or appears to be attracted to a rival.
  • New research suggests jealousy is only 30 percent heritable. Nonshared environmental factors explain the rest of the variation in jealousy.
  • Jealousy is associated with having a lower mate value, lack of trust in one’s partner, having been cheated on, and restricted sociosexuality.
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Using a sample of 5,660 Finnish twins and their siblings, a recent study by Kupfer et al., published in the January issue of Evolution and Human Behavior, examines the genetic and environmental causes of jealousy, finding it to be a partly heritable trait.

What is romantic jealousy?

Romantic jealousy refers to thoughts, feelings, or actions that occur in response to self-esteem or relationship threats concerning a real or imaginary romantic attraction between one’s romantic partner and a potential rival.

What is the function of jealousy? Evolutionary views suggest jealousy functions to motivate mate guarding and mate retention behaviors.

Some examples of negative mate-retention behaviors are emotional manipulation, hypervigilance (e.g., needing to know where one’s romantic partner is at all times), threatening one’s romantic partner, and threatening potential rivals. (For a discussion of positive and negative mate retention behaviors, see this article).

Though jealousy is a universal experience, some people tend to experience more jealousy than others. But are such variations in jealousy due to genetic factors? Environmental ones? Or both?

Investigating romantic jealousy

Sample: 7,726 participants (5,660 twins and their siblings); 5,197 in a romantic relationship; 471 had cheated on a romantic partner, 187 had been cheated on, and 160 had experienced both. The twins’ average age was 29 years old (range of 18-45 years), while their siblings had an average age of 32 years old (range of 18-58 years).


  • Romantic jealousy: Participants reported how comfortable they would feel if their romantic partner behaved in ways that might evoke jealousy, such as touching another person while speaking with them or kissing the person on the lips.
  • Mate value discrepancy: Participants were asked, “Overall, how would you rate your level of desirability as a partner on the following scale compared to others of the same sex?” Those in a relationship also answered how they would rate their partner’s desirability.
  • Partner’s trustworthiness: Those presently in a romantic relationship were asked, “How much do you trust your partner?”
  • Sociosexual orientation: The Sociosexual Orientation Inventory assessed sociosexuality (i.e., inclination toward engaging in uncommitted sex), including sociosexual desire, behavior, and attitude (e.g., “Sex without love is okay”).
  • Cheating: Participants responded to the question, “How many times have you been cheated on in a committed, exclusive relationship?” Those currently in a romantic relationship answered additional questions about cheating. Overall, nearly a third reported having been cheated on at least once.

Genetic and environmental causes of jealousy

The results showed genetic factors explained 29 percent of the variation in jealousy. Nonshared environmental factors explain the rest. Note, nonshared environmental factors are experiences the twins did not share (e.g., going to different schools), while shared environments, like parenting, are experiences the twins had in common.

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So, what are the implications of the fact that familial or shared environments do not appear to influence jealousy? For one, the present findings are inconsistent with models based on attachment theory. These models suggest children learn from their parents what to expect in a relationship; and their expectations determine if they, as adults, respond with jealousy to relationship threats (e.g., when their partner pays attention to a person of the opposite sex).

In contrast to parental transmission accounts of jealousy just discussed, other views, such as mate-guarding accounts, explain jealousy by emphasizing nonshared environments.

Mate-guarding views of jealousy suggest jealousy is influenced by factors like the desirability of a person’s romantic partner, qualities of the rivals, trust issues, history of infidelity, mate value discrepancy (e.g., having a partner who is much more attractive than oneself), and sociosexuality.

Examining some of these factors, the present study found that “the strongest predictors of jealousy were more restricted sociosexual attitude and desire.” Why? Perhaps because sociosexually-restricted individuals (those less willing to have casual sex) have a smaller number of romantic relationships, so they are more protective of them. Of course, we cannot rule out the opposite causality: Perhaps more jealous people pursue exclusive relationships as a way to make infidelity less likely.

In general, individuals who reported higher jealousy had the following characteristics:

  • Felt their romantic partner was not trustworthy.
  • Believed they were less attractive than their romantic partner.
  • Had actually been cheated on in the present or a past romantic relationship.


The investigation found that “people differ in jealousy partly because of genetic influences, but mostly because of nonshared environmental influences.”

In short, genes and shared childhood environments and experiences (e.g., parenting) have less of an influence on jealousy compared to the unique experiences or beliefs of the individual—e.g., having been cheated on or believing one is much less attractive or desirable than their romantic partner.

Facebook image: Song_about_summer/Shutterstock

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