Similarity in Relationships: How Shared Traits Foster Attraction

There’s a reason you tend to click with people who share your sense of humor, political views, or favorite weekend activities. The pull toward people who are like us isn’t coincidence – it’s one of the most well-documented patterns in social psychology. Researchers have studied this phenomenon for decades, and the findings consistently point to the same conclusion: similarity is one of the most powerful drivers of interpersonal attraction. Understanding why – and how – this works can shed real light on how our friendships and romantic relationships form, deepen, and endure.

The similarity-attraction effect: what the research says 🔗

Similarity-attraction theory holds that people are more drawn to others who resemble them across a range of characteristics – attitudes, values, personality traits, and even demographic backgrounds. This idea is so consistently supported in the research literature that one scholar famously referred to it as a “law” of human social behavior. The effect has been observed across friendships, romantic relationships, and even workplace dynamics.

One of the foundational studies in this area was conducted by Theodore Newcomb in 1961. Newcomb randomly assigned male undergraduates to live together as roommates without prior acquaintance and tracked how friendships formed over time. His findings showed that demographic similarity and attitude similarity were powerful predictors of who would become friends . Students who shared similar values, political views, and academic backgrounds were far more likely to form close bonds than those who differed on these dimensions. This study laid much of the groundwork for what would become a robust body of research on similarity and attraction.

What kinds of similarity matter? 🔗

Similarity isn’t a single thing – it spans multiple dimensions, and research has identified several that are particularly relevant to attraction.

Attitudes and values 🔗

Attitude similarity is the most extensively studied form of similarity in the attraction literature. Donn Byrne and his colleagues, using a “bogus stranger” methodology in which they varied the degree of attitudinal similarity between a perceiver and a stranger, demonstrated across a series of studies that attitude similarity consistently produced greater liking of the target. The explanation Byrne and Clore offered was straightforward: when someone shares your attitudes, it validates your view of yourself and the world, which is inherently rewarding.

Research by Jones and Stanton examined how belief similarity related to marital satisfaction and found that perceived similarity in couples’ belief systems was negatively associated with marital distress. Similarly, similarity in activities and interests has also been associated with relationship satisfaction, with research showing that engaging in joint activities is linked to couples reporting higher levels of connection.

Demographic and social background 🔗

In a 1988 study, Lydon, Jamieson & Zanna suggested that interpersonal similarity and attraction are multidimensional constructs in which people are attracted to people similar to themselves in demographics, physical appearance, attitudes, interpersonal style, social and cultural background, personality, preferred interests and activities, and communication and social skills.

Byrne, Clore and Worchel in 1966 suggested that people with similar economic status are likely to be attracted to each other, and Buss & Barnes in 1986 also found that people prefer their romantic partners to be similar in certain demographic characteristics, including religious background, political orientation, and socioeconomic status. These findings reflect how shared social positioning creates a common frame of reference that makes interaction feel natural and comfortable.

Personality traits 🔗

Researchers have shown that interpersonal attraction is positively correlated with personality similarity – people are inclined to desire romantic partners who are similar to themselves on agreeableness, conscientiousness, extraversion, emotional stability, openness to experience, and attachment style.

An important nuance here is the distinction between actual and perceived similarity. Research findings suggest that perceived similarity is a more significant predictor of attraction than actual similarity. This means that what matters most isn’t whether two people are objectively alike, but whether they believe they are. At a first meeting, speed-dating study data confirmed that perceived, but not actual, similarity significantly predicted romantic attraction.

Physical appearance 🔗

Similarity in physical attractiveness also plays a role. The matching hypothesis, proposed by sociologist Erving Goffman, suggests that people are more likely to form long-standing relationships with those who are equally matched in social attributes like physical attractiveness, and the study by Walster and Walster supported this by showing that partners who were similar in terms of physical attractiveness expressed the most liking for each other. A related study on randomly assigned college roommates found that similarity in personality and attractiveness both resulted in greater satisfaction with roommate relationships.

Why does similarity lead to attraction? 🔗

Several psychological mechanisms explain why we tend to like people who are similar to us. Research has identified at least four explanations with consistent empirical support.

First, similar others are more likely than dissimilar others to possess opinions and worldviews that validate one’s own, meaning that interaction with similar others is a likely source of social reinforcement. Second, people more readily anticipate rejection by dissimilar others, and since anticipated rejection diminishes attraction, similarity reduces this social threat. Third, interaction with similar others may be more enjoyable because similar others tend to share one’s own interests, values, and activity preferences. Finally, because shared values and attitudes shape behavior in similar ways – for example, both people enjoying the same type of activities – similar people are simply more likely to encounter each other in the first place.

Byrne and Clore extended the reinforcement-affect model to explain that the discovery of interpersonal similarity leads to validation of one’s own characteristics and views by providing consensus support, which then leads to a higher perceived appropriateness of one’s current beliefs, attitudes, behaviors, and traits.

The attraction-similarity model: when attraction shapes perception 🔗

Most people assume the causal arrow runs in one direction: we notice similarity and then feel attracted. But research suggests the relationship is bidirectional. The attraction-similarity model, grounded in balance theory, proposes that attraction itself motivates people to perceive greater similarity.

The attraction-similarity model uses balance theory to argue that individuals are motivated to perceive similarities in order to obtain a balanced relationship, and supporting this, people perceive similarities between themselves and their friends based on projections of the self.

This was tested directly by Morry (2005), who examined whether satisfaction in ongoing friendships predicted perceived similarity – rather than the other way around. Consistent with the attraction-similarity hypothesis, the more satisfied individuals were with their friendships, the more similar they perceived their friends to be to themselves. This suggests a self-reinforcing cycle: initial attraction fosters feelings of similarity, which in turn deepen the relationship.

The attraction-similarity hypothesis also predicts that as attraction increases, perceptions of similarity should also increase, suggesting that as satisfaction in a friendship or dating relationship develops, this should predict subsequent perceptions of similarity. Over time, research shows that partners do converge – in emotional expression, values, and even communication styles – making them genuinely more alike as the relationship grows.

Similarity and relationship satisfaction over time 🔗

The role of similarity doesn’t end at first attraction – it continues to shape how relationships develop and whether they thrive.

Among the countless studies on spousal relationships, similarity between personality types appears to be a key determinant in marital satisfaction. Married individuals who have greater similarities with their partners are likely to have higher levels of relationship satisfaction, and dating couples with similarity in affectively oriented communication skills report higher levels of partner attraction and relationship satisfaction.

A longitudinal perspective adds further nuance. Research by Lea and Duck demonstrated that similarity in general attitudes was a strong predictor of initial attraction, but over time, similarity in a more concentrated set of attitudes – specifically personal constructs that reflect one’s core worldview – emerged as the stronger predictor of satisfaction. This suggests that what draws people together initially may be different from what sustains them in the long run.

More recent work published in the European Journal of Social Psychology has explored the mechanisms linking perceived similarity to relationship satisfaction. People who perceive similarity in emotions are more likely to have better relationship outcomes such as perceived love and responsiveness. Perceived similarity also increases attributional confidence – the sense that you can reliably predict and understand your partner – which reduces uncertainty and strengthens relational bonds.

Does similarity always predict attraction? Limits of the theory 🔗

The evidence for similarity-attraction is strong, but it isn’t without limits. Some researchers, such as Milton Rosenbaum in a 1986 study, have suggested that attitudinal dissimilarity, rather than attitudinal similarity, drives the similarity-liking link – with people’s motivation to avoid social interactions with dissimilar others being as strong as, or stronger than, their desire to affiliate with like-minded others.

A meta-analysis of numerous similarity-attraction studies found that while similarity manipulations have strong effects on attraction in laboratory settings, these effects are more limited in real long-term relationships. This doesn’t mean similarity doesn’t matter in real life – it does – but other factors like commitment, trust, and shared experiences also play significant roles over time.

Research confirms that the similarity-attraction hypothesis is valid in organizational and social settings and represents a fundamental force driving interpersonal behavior, but this force is not so strong that it cannot be overridden or moderated by other psychological, social, or contextual forces.

There’s also the question of which similarities matter most. Individuals reliably feel more attracted to those with whom they share similar attitudes, but this affective liking does not always predict affiliative behavior such as pursuing a friendship – suggesting that attitude strength and personal importance of the shared characteristic play a moderating role.

Similarity beyond romantic relationships 🔗

The pull of similarity isn’t limited to romantic contexts. A large-scale field study collected data from 1,523 interacting pairs across 11 independent samples and found that within-dyad similarity was statistically significant on 86% of variables measured , including personality traits, attitudes, values, recreational activities, and behaviors. This finding held up across a wide range of natural social settings, suggesting that similarity shapes not just who we fall in love with, but the full landscape of our social world.

In friendships specifically, studies published in the Journal of Social and Personal Relationships have found that people tend to form friendships with others who are similar to themselves in terms of values and interests, a pattern that holds across friendships, romantic relationships, and work environments alike.

What do you think? If perceived similarity matters more than actual similarity in driving attraction, what does that suggest about the role of self-awareness in how we connect with others? And considering that satisfaction itself can increase perceptions of similarity over time, do you think we grow more alike as our relationships deepen – or do we simply start to notice similarities that were always there?

References

1. https://www.encyclopedia.com/social-sciences/applied-and-social-sciences-magazines/similarityattraction-theory
2. https://en.wikipedia.org/wiki/Theodore_Newcomb
3. https://psychology.iresearchnet.com/social-psychology/interpersonal-relationships/similarity-attraction-effect/
4. https://journals.sagepub.com/doi/10.1177/0265407505054524
5. https://onlinelibrary.wiley.com/doi/10.1002/ejsp.3085
6. https://quantpsy.org/pubs/bahns_crandall_gillath_preacher_2017.pdf