Is Jealousy Natural?

Psychology and neuroscience weigh in on whether jealousy is innate or cultural

In my previous article about jealousy, I showed that most violence against women in Western societies is intimate partner violence (also called domestic violence), and presented evidence that it is caused by jealousy. I further argued that jealousy is driven by false beliefs of our monogamy culture. By questioning those beliefs in real life, polyamory can help people deprogram their jealousy and reduce violence in relationships.

One of these beliefs is that jealousy is natural, that is, driven by innate biological compulsions outside our control. This has been reinforced by views about human reproductive behavior promoted by sociobiology and evolutionary psychology.

Is this belief is correct, then polyamory would be a fool’s errand, doomed to failure because having multiple romantic partners would inevitably elicit jealousy in them and lead to endless drama.

On the other hand, if jealousy is caused by culture, it would be possible to deprogram it. Not only this would make polyamory possible, but it could also lead to healthier monogamous relationships and help eliminate intimate partner violence.

My girlfriend cheated on me, and I didn’t get jealous

In 1980, I was drafted into the Spanish army and got separated from my girlfriend. After spending a month confined in the barracks, I could finally go back to Madrid and see her.

Something was off. She finally confessed that she had sex with another guy. She was torn by guilt. I sat there, waiting to feel angry, but jealousy never came. Instead, I felt vaguely glad that she had enjoyed herself. There was beauty in the story of her affair. I couldn’t satisfy her sexually while I was away, so it was natural that she sought that from someone else.

However, my girlfriend found it weird that I was so quick to forgive her. Didn’t that mean that I didn’t love her? These doubts entered my mind as well.

I didn’t come to my non-jealousy spontaneously. Although polyamory had not been invented at the time, books by Erich Fromm (The Fear of Freedom, The Art of Loving) and Aldous Huxley (Island) had planted the seed of ethical non-monogamy. I had read them and knew that overcoming jealousy was possible and healthy.

What is jealousy?

I was feeling insecure You might not love me anymore I was shivering inside I was shivering inside Oh, I didn’t mean to hurt you I’m sorry that I made you cry Oh no, I didn’t want to hurt you I’m just a jealous guy

Jealous Guy — John Lennon

We experience jealousy when somebody switches their attention and care from us to another person. Jealousy is not exclusive of romantic love. It can exist between siblings, between a parent and a child, or between friends. However, there is something that feels different about romantic jealousy — the one triggered when we suspect that our spouse or lover is attracted to another person. It arises easily and can become obsessive. It hurts a lot, to the point of damaging our self-esteem and driving us to prolonged grief. Does this mean that romantic jealousy is hard-wired in our brains?

It is not clear if jealousy is a single emotion, a mixture of emotions, or a complex response involving emotions, cognition and culture.

“Romantic jealousy is usually conceptualized as an amalgamation of various emotions: anger, frustration, insecurity, unluckiness, helplessness, sadness, grief, shame, embarrassment and humiliation” (Pichon et al., 2020).

Sexual jealousy and emotional jealousy

There are two types of romantic jealousy.

• Sexual jealousy is triggered by suspecting that our partner is having sex with another person.
• Emotional jealousy is triggered by imagining that our partner loves another person.

These two different types of jealousy establish the difference between open relationships and polyamory. Open relationships allow for sex outside the couple, but only as long as it does not include emotional attachment. In them, people overcome sexual jealousy but not emotional jealousy. Polyamory allows both sexual and emotional intimacy between more than two people. This requires that everybody is able to manage both sexual and emotional jealousy. This doesn’t mean that jealousy disappears in open or polyamorous relationships, only that people deal with it without letting it get out of control and hurt others.

‘Jealousy as a specific innate module’ hypothesis

Some evolutionary psychologists have proposed that sexual jealousy is more common in men and emotional jealousy is more common in women. They argue that this is because the two sexes follow different reproductive strategies, and that jealousy is innate.

Christine R. Harris, a scientist at the University of California, San Diego, called this hypothesis ‘Jealousy as a specific innate module’ (JSIM) (Harris, 2003):

“The specific innate modular theory of jealousy hypothesizes that natural selection shaped sexual jealousy as a mechanism to prevent cuckoldry, and emotional jealousy as a mechanism to prevent resource loss. Therefore, men should be primarily jealous over a mate’s sexual infidelity and women over a mate’s emotional infidelity.”

In other words, men want to have as many children as possible because they invest little energy in producing semen and mating. They also leave a lot of the work of raising children to women. Still, inasmuch as they devote resources to caring for children, they want to make sure that they are their own offspring and not that of other men. Therefore, men are driven to have sex with other men’s wives while preventing their wives to have sex with other men. This gives rise to sexual jealousy.

In contrast, women are always sure that the children born out of their belly carry their genes, so they do not have to feel sexual jealousy. However, they need their mate to help provide the resources to raise those children to adulthood. If the man becomes emotionally attached to another woman, he may end up helping her raise her children instead. This leads women to feel emotional jealousy.

Evidence against the innate jealousy hypothesis

The reasoning behind the JSIM hypothesis seems quite solid. It may be true in many animal species. However, its applicability to humans is in doubt.

In her paper (Harris, 2003), Christine R. Harris analyzes several lines of evidence in the scientific literature in support of the JSIM hypothesis. In them, differences between men and women in sexual and emotional jealousy were taken as evidence for JSIM.

One line of evidence was questionnaires asking what is more upsetting: a mate falling in love or having sex with someone else. Papers using this method found differences between men and women. However, participants could only choose between two options. If continuous rating scales were used instead, both men and women considered emotional infidelity more distressing. In countries other than the United States, men reported that they find emotional infidelity more upsetting. When real experiences of infidelity were examined instead of imagined infidelity, the differences between the sexes vanished again.

To avoid the problems of using questionnaires, scientists could measure changes in heart rate and skin conductance (electrodermal activity) to assess how upset people get when imagining infidelity. Initially, it was found that men had higher responses to sexual infidelity. However, responses of men to sexual images unrelated to infidelity were also stronger, suggesting that men were responding to sex in general and not to infidelity. Women responded more to emotional infidelity with electrodermal activity, but not with changes in heart rate. Moreover, women in committed relationships showed more reactivity to sexual infidelity than emotional infidelity.

Another line of evidence in favor of the JSIM hypothesis was based on statistics on domestic violence. But, as I discuss in my previous article on jealousy, intimate partner violence is driven by cultural beliefs about monogamy and infidelity.

Finally, instances of pathological jealousy have been used to support the JSIM. However, these are cases of people with underlying mental diseases and thus cannot be used to support a biological mechanism common to everybody.

Therefore, sexual and emotional jealousy seem to occur equally in men and women. This cannot be used to support a biological, innate cause for jealousy.

Harris finishes her paper by discussing alternatives hypothesis to explain jealousy:

“Social-cognitive theorists have particularly emphasized the importance of two factors that can impact the likelihood of experiencing jealousy: (a) when relationship rewards are threatened and (b) when some aspect of a person’s self-concept, self-regard, or other representations of oneself is challenged by a rival.” — (Harris, 2003)

Monogamous voles, oxytocin and vasopressin

We have a new window into monogamy based on neuroscience and studies on a field mouse called the prairie vole (Microtus ochrogaster). Prairie voles are strictly monogamous: they form lifelong bonds, nest together, groom each other, and take care of their offspring together. In comparison, the montane voles (Microtus montanus) are complete sluts: males mate with multiple females, and the female estrus is triggered by the proximity of any male. Scientists wondered how animals so closely related could have such different mating behaviors.

They tracked down these differences to the neuropeptide oxytocin and its receptors in the brain. In the blood, oxytocin is a hormone that induces uterine contractions during labor and milk production. However, in the brain its main function is to induce social and pair bonding (Young et al., 1998). The brain of the puritanical prairie voles is loaded with oxytocin receptors, particularly in the reward pathway of the nucleus accumbens, while the promiscuous montane voles have fewer receptors in this area. Oxytocin also reduces responses to distressing pictures and the activation of the amygdala, the part of the brain that generates fear and anxiety (Stein, 2009). A similar neuropeptide, vasopressin, also modulates pair bonding, as well as territoriality in males (Young and Wang, 2004).

There is ample evidence that oxytocin does the same thing in humans as in voles. For example, when men in monogamous relationships were given intranasal oxytocin (a way to get it into the brain), they keep a greater distance between them and attractive women (Scheele et al., 2012). This was not observed in single men. Hence, it seems that oxytocin promotes fidelity by making men avoid signaling romantic interest to women who are not their partner.

Oxytocin and jealousy

Therefore, whether we are monogamous or promiscuous seems to come down to the number of oxytocin and vasopressin receptors that we have in our brains. It is tempting to jump to the conclusion that there are people who are naturally monogamous — with loads of those receptors in their brains — while other people are naturally promiscuous — with brains impoverished in oxytocin and vasopressin receptors.

This seems to contradict the findings of psychologists that I mentioned earlier. If monogamous behavior is controlled by a few genes — those encoding oxytocin, vasopressin and their receptors — then jealousy should also be innate, shouldn’t it?

Not so fast! A recent double-blind, placebo-controlled study (Zheng et al., 2021) gave intranasal oxytocin to 70 couples and then measured their jealousy while they imagined partner infidelity or played a game that simulated being excluded by a rival from interacting with their partner. Surprisingly, oxytocin decreased jealousy in both men and women. The couples that received oxytocin reported feeling more positive emotions and interacted better with the rival during the game. The scientists concluded that oxytocin reduced jealousy and its emotional impact.

Another study (Preckel et al., 2015) showed that oxytocin reduced the upset produced by images of infidelity. This was tracked down to less stimulation of the anterior cingulate cortex, a part of the brain that responds to social and moral conflict.

So one of the ways oxytocin maintains the bond in monogamous relationships is by reducing jealousy and the conflict it entails.

The belief that jealousy is a proof of love has been debunked by science. It’s actually the opposite: jealousy kills love.

Take-home message

Much remains to be said about monogamy and its relationship with oxytocin and vasopressin, but I leave that for future articles.

I think that I have answered the question in the title: jealousy is not natural or innate. It is not a behavior created by evolution so that men can protect their paternity and women can ensure the cooperation of men to raise their offspring. Even though monogamous behavior seems to be controlled by certain genes, jealousy is not part of that behavior. Quite the opposite: the stronger the pair bond, the weaker the jealousy.

Jealousy appears to be a cognitive and social construct, a series of beliefs driven by religion and social norms. If jealousy has been socially programmed, that means that we can be deprogrammed not to feel it or, at least, not to be hurt by it. Given the amount of violence that jealousy produces, especially against women, that is really good news.

Copyright 2021 Hermes Solenzol