New research published in Journal of Personality Research suggests that whether one feels satisfied in a romantic relationship is highly dependent on the specific combination of how one views oneself and one’s partner. Rather than a simple rule of opposites attract or birds of a feather, this research shows that alignment on political views tends to benefit couples, while perceiving your partner as kinder than you produces the best relationship quality. These patterns provide evidence that romantic success depends on psychological rules that differ depending on the specific traits valued and the cultural background of the couple.
Marta Kowal, a researcher at the Institute of Psychology at the University of Wrocław in Poland, designed the study to address a persistent mystery in relationship science. Past studies have yielded mixed results regarding whether romantic partners need to be similar in order to be happy.
“There’s a saying that opposites attract, but scientific evidence largely suggests otherwise and that people who are more similar tend to have more satisfying relationships,” Kowal said. “At the same time, some studies have reported the opposite pattern.”
Kowal found that previous studies relied heavily on people in Western, educated, industrialized, affluent, and democratic societies – people often referred to as “queer groups.” The lack of diversity has left a gap in understanding how universal these romantic preferences are.
“Additionally, much of what we know comes from the WEIRD samples,” Kowal explained. “Thus, by utilizing a large dataset of 41,606 individuals from 74 countries, we have an excellent opportunity to consider when similarity matters, when partner idealization matters, whether these associations depend on the specific characteristics being considered, and, ultimately, whether these patterns are consistent across cultures.”
To explore these dynamics, researchers analyzed data from tens of thousands of individuals currently in romantic relationships. These participants completed an online survey translated into their local language and answered questions about their relationship status and length of partnership.
The study asked people to rate themselves and their romantic partners on nine traits. These characteristics include health, kindness, physical attractiveness, religiosity, resources, social class, education, political orientation, and age. Participants rated both themselves and their significant others using simple numbered scales, including an 11-point scale for health and attractiveness.
To measure relationship quality, this study used an established psychological questionnaire. Participants completed an abbreviated version of the Triangular Love Scale, which categorizes love into intimacy, passion, and devotion. They also completed a Relationship Satisfaction Scale to report how satisfied they were with their partnership overall.
Kowal used special statistical techniques to simultaneously compare self-ratings and partner ratings. This mathematical approach allowed the researchers to see what happens when partners are perfectly matched and when one is rated higher than the other.
The data showed that kindness and physical attractiveness were the strongest predictors of high-quality relationships. A concept known as partner idealization emerged as crucial to these socially desirable characteristics.
“The size of the effect varies greatly depending on the trait,” Kowal told SciPost. “Tenderness was the strongest predictor. Participants’ self-ratings and partner ratings of kindness together accounted for approximately 21% of the variance in relationship satisfaction, which is quite large for a single trait assessed with a single item.”
Participants reported the highest levels of love and satisfaction when they believed their partner was kinder and more attractive than them. “Physical attractiveness was just as strong,” Kowal added, but noted that values and demographic characteristics had a more modest effect overall.
“Perhaps the most intuitive conclusion is that when it comes to universally valued qualities (such as kindness and physical attractiveness), what seems most important is not that you and your partner are equal, but that you perceive your partner as very kind and attractive, ideally even more so than yourself,” Kowal explained.
Furthermore, these positive traits exhibit an additive effect, meaning that relationship quality is highest when individuals rate both themselves and their partner very highly. This means that a baseline of mutual tenderness will form a strong foundation for romance.
“Importantly, this partner idealization effect goes hand-in-hand with a strong ‘more is better’ pattern, with relationship quality being highest when both partners are perceived to be high on these traits,” Kowal said.
For value-based traits such as political orientation, the pattern appeared quite different. For political beliefs, strict similarity was the strongest predictor of happy relationships.
“However, for values-based traits (particularly political orientation), similarity matters in a more symmetrical sense. Regardless of which direction the gap falls, the more distant people perceive themselves and their partner to be, the worse their relationship quality tends to be,” Kowal said.
Political disagreements predicted lower relationship quality, no matter which partner moved to the left or right. “So ‘opposites attract’ is almost a myth, but the reason really depends on what dimension we are talking about,” Kowal pointed out.
Although the researchers expected there to be significant differences in how men and women evaluated their partners’ traits, the results showed a fairly consistent pattern across genders. These results are quite remarkable, as past evolutionary theories have often suggested that men and women prioritize very different qualities in their mates.
“I was actually quite surprised by the small gender difference,” Kowal says. “Given the long-standing debate in evolutionary psychology about sex differences in mate preference, I expected to find more pronounced asymmetries.”
Kowal predicted that men’s relationship quality would be more strongly related to their partner’s physical attractiveness than women’s. Although some small differences emerged, they were not the defining feature of the data.
“While there were some domain-specific gender differences (for example, men reported higher passion when partnered with a younger partner and higher relationship satisfaction when they perceived themselves to be more right-wing than their partner), these were the exception rather than the rule,” Kowal said. “In general, men and women were pretty much in agreement.”
Culture, on the other hand, played a big role in shaping what people value in their partners. Kowal classified countries based on several cultural indicators, including human development, gender equality, individualism, and relationship fluidity. Relational mobility refers to the degree of freedom individuals have in a society to choose or break up with romantic partners.
“Another important finding is the existence of cross-cultural differences,” Kowal noted. “Specifically, the patterns of associations across the three trait domains differed across 74 countries. Cultural characteristics (e.g., human development index (HDI), individualism, gender equality, and relationship fluidity) moderated many of the observed associations.”
In countries with high relationship fluidity and highly individualistic modernity, socially desirable traits such as kindness and attractiveness had the strongest influence on relationship well-being. In less modern countries, the rules have shifted to status and demographic characteristics. This means that congruence between social class and educational attainment is a stronger predictor of relationship stability.
Although this study features an impressive global sample, its reliance on self-reported data means that the results capture subjective perceptions rather than objective reality. Because the data include only one partner’s perspective, it measures perceived rather than actual similarity.
“The most important limitation is that this study relied on individual-level, self-reported perceptions rather than dyadic data from both partners,” Kowal explained. “This means that what we are capturing is perceived similarity and perceived partner characteristics, rather than actual similarity or objectively assessed characteristics.”
People who are deeply in love may see their partner through rose-colored glasses and think more highly of their partner simply because they feel happy. This psychological habit makes it difficult to determine exact cause and effect.
“That’s not necessarily a weakness (perceived similarity is often a better predictor of relationship quality than actual similarity), but it does mean we can’t rule out the possibility that relationship quality itself is partially driving the pattern,” Kowal said. “People in love tend to perceive their partners more favorably, which may increase the observed partner idealization effect.”
Future research should examine both members of the couple over an extended period of time. This step helps determine whether actual similarity is as important as perceived similarity. Tracking couples over the years can also help explain how these perceptions change as the relationship ages and faces new challenges.
The study, “Partner idealization and perceived partner similarity predict relationship quality in 74 countries,” was conducted by author Marta Kowal.
