If you were living vicariously through TV love stories this Valentine’s, you may have noticed a familiar trope. From Shakespeare’s Romeo and Juliet to today’s Shane and Ilya, audiences love a forbidden romance: two people divided by family, society or circumstance, choosing each other against the world. Psychologists have a name for this idea: the Romeo and Juliet effect.

The theory was coined in 1972, when researchers surveyed 140 couples and found a positive correlation between parental interference and romantic love. They explained the finding using reactance theory, which proposes that when people feel their freedom being threatened, they are motivated to restore it; if your parents disapprove of your partner, loving them becomes an appealing act of defiance.

“From Shakespeare’s Romeo and Juliet to today’s Shane and Ilya, audiences love a forbidden romance”

In the paper, the researchers quoted novelist Edith Hamilton: “The more the flame is covered up, the hotter it burns.” Perhaps it is no surprise that such a romantic psychological theory quickly gained traction in popular culture, blogs and relationship advice columns.

However, the story doesn’t end there. When researchers in 2014 attempted to replicate the original study, they reached entirely the opposite conclusion. Instead of strengthening love, disapproval from friends and family seemed to predict lower relationship quality. In fact, in the decades since the Romeo and Juliet effect was first proposed, further studies have largely failed to support it, instead finding evidence for an alternative theory: the social network effect.

According to this theory, relationships thrive when embedded within supportive networks. Approval from friends and family is associated with greater stability and commitment. This approval can be explicit, like telling a couple they’re ‘perfect together’, or indirect, like inviting them to events as a pair, or liking their Valentine’s posts on Instagram. Social media may even enhance the effect since it makes social validation more accessible, with studies finding that greater overlap in a couple’s Facebook posts predicts stronger commitment. Interestingly, perception may matter even more than objective reality; people believing that others approved of their relationship was more strongly linked to relationship quality than the approval itself.

“This approval can be explicit, like telling a couple they’re ‘perfect together’, or indirect, like inviting them to events as a pair”

Networks shape relationships in other ways, too. They influence not only how relationships are maintained, but how they begin: in experimental studies, people are more likely to pursue potential partners endorsed by their friends. Once formed, couples with mutual friends tend to be more stable. At the same time, networks can have negative effects: there is evidence that having close friends outside the relationship can reduce emotional dependence on a partner and weaken the connection. If maintaining a large network detracts from the time and effort invested in a relationship, it is likely to suffer as well.

“For relationships facing prejudice or stigma, the social network effect becomes especially salient”

What about Heated Rivalry’s Shane and Ilya? For relationships facing prejudice or stigma, including same-sex or interracial relationships, the social network effect becomes especially salient. Research has found that reduced social support can lead to stress that erodes commitment over time. Relationship secrecy is another mechanism: being forced to conceal a relationship, whether from family or the public, has been linked to lower relationship quality.

So is the Romeo and Juliet effect entirely false? Not necessarily. In response to the failed attempts to replicate the original study’s findings, one of its authors commented that the increase in romantic love they observed in 1972 was accompanied by increases in distrust and criticism. In other words, heightened romantic feelings did not necessarily mean healthier love, which could reconcile it with the social network effect.

Meanwhile, the authors of the 2014 study revisited their data and found that people whose behaviour followed the Romeo and Juliet effect differed systematically from those who fit the social network effect. These ‘Romeos and Juliets’ reported greater support from friends, stronger individualistic values, and a more independent sense of self. Forbidden love, it seems, may flourish under certain conditions, but is far from universal.

The Romeo and Juliet effect makes for a compelling Valentine’s watch. The science, however, paints a more realistic picture: the strongest relationships are not those that burn hottest under pressure, but those supported by the world around them.