A sweeping new review of nearly 340 studies has cast doubt on the widely held belief that similarities between long-term romantic partners are the key to relationship satisfaction and longevity. While the idea that “birds of a feather flock together” dominates Western thinking, the research finds that actual similarity in personality, interests, and background may play a much smaller role in relationship success than previously assumed. Instead, it appears the feeling of being similar to one’s partner—rather than measurable overlap—could matter most for lasting happiness together (PsyPost).
Thai readers, who often navigate the crossroads of tradition and modernity in romantic relationships, may find the study’s findings particularly relevant. As Thailand’s social values shift—balancing centuries-old beliefs about partnership with the influence of global dating culture—the role of compatibility and shared values remains a central question for couples throughout the kingdom.
The meta-analysis, published in the Journal of Social and Personal Relationships, meticulously reviewed 339 scholarly studies from across the globe, covering research conducted between 1937 and 2024. According to the review, which drew mostly from studies in the United States and other Western countries, couples’ actual similarity across six main domains—beliefs and values, demographics and background, lifestyle and interests, personality, physical characteristics, and romantic habits—showed only a modest and often inconsistent link to higher relationship satisfaction or lower rates of breakup and divorce.
Drifting from popular dating narratives, the lead author, a PhD candidate at the University of Michigan, explained: “We do not see evidence that being similar to your romantic partner affects your relationship quality or whether or not you stay together with your partner. This is true across different domains of similarity, such as demographics, beliefs and values, and lifestyle. However, there is more evidence that perceived similarity (thinking you are similar to your partner) is positive for relationships.”
To reach these conclusions, the research team conducted a scoping review, an approach designed to find patterns and gaps in large and diverse bodies of research. Over 7,600 scholarly articles were initially identified, with nearly 340 making the final cut based on relevance and methodological rigor. Most studies featured long-term, mostly heterosexual and married couples, and measured either actual similarity (using questionnaires completed by both partners) or perceived similarity (one partner’s impressions about how alike their partner seemed).
The review found the strongest evidence in demographic similarities, such as race or education, but even here the link was far from universal. Most notably, the perception of similarity—regardless of actual shared traits—was consistently linked to higher satisfaction and relationship stability, suggesting the role of shared worldview, communication, and supportive behaviors may outweigh strict trait matching.
The review also highlighted how statistical methods affected the findings. Simpler matching techniques often reported stronger benefits for similarity, while studies that controlled for confounding variables (for example, people’s tendency to rate themselves and their relationships highly) found weaker or no effects. This nuanced approach raises questions about the accuracy of earlier, less sophisticated research in relationship science.
For Thailand, where many couples face social expectations to choose partners from similar backgrounds—whether by ethnicity, religion, or class—the review’s findings challenge longstanding assumptions. The importance placed by Thai families and communities on shared values and status, prominent in matchmaking traditions and social rituals, contrasts with the data showing only a modest benefit from such similarities in predicting lasting happiness.
Culture also shapes how Thais perceive and talk about love. In the Thai language, the concept of “khwam samankan” (ความสัมพันธ์)—deep connection or relationship—is often understood as the harmonious blending of personalities and worldviews, not just matching traits on paper. This aligns with the study’s finding that perceived similarity, more so than actual measured overlap, is linked to satisfaction. In practice, Thai couples may intuitively cultivate this sense of connection through shared experiences, rituals, and the gradual building of mutual understanding, regardless of initial differences.
Despite these important conclusions, the review notes several limitations. Most of the studies examined were published in English and focused on Western couples, raising questions about generalizability to Thai or broader Asian contexts. Furthermore, the review focused on long-term couples and did not examine early dating or other kinds of interpersonal relationships, leaving open the possibility that similarity plays a bigger role at the start of relationships or in different relational dynamics common in Thailand.
Thai relationship counselors and psychologists have long debated whether couple matching should focus on values, family backgrounds, or practical compatibility. According to a senior clinical counselor at Ramathibodi Hospital’s Marriage Guidance Center, “Many Thai couples come in believing that differences will eventually lead to conflict, but we often see that those who communicate openly and work through their differences develop even stronger bonds. The sense that they are similar sometimes follows from that process, rather than predicting it from the start.”
Moreover, the finding that perceptions matter more than facts has important implications for counseling and self-understanding. “If couples focus on building empathy and recognizing common ground, they may feel more satisfied and committed—even if their backgrounds or personalities are quite different,” notes an educational psychologist at Mahidol University. This is especially significant in Thailand’s increasingly multicultural urban centers, where diverse values and lifestyles increasingly intersect through workplaces, schools, and social opportunities.
Historically, arranged marriages and family matchmaking have played a key role in Thai society. Shared community ties, religious beliefs, and family backgrounds were seen as essential to marital stability. This tradition has gradually shifted as younger Thais—especially in Bangkok, Chiang Mai, and other urban areas—opt for love-based marriages and embrace global trends such as online dating. Yet, tensions between old and new ways persist, and the belief in the lasting importance of similarity continues to shape expectations.
Looking forward, the review’s authors call for more nuanced research, especially studies capturing the evolving realities of relationships in non-Western societies like Thailand. “Our main finding presents an interesting tension—that perceptions of similarity may be important, though there is little evidence that actual similarity is. I hope to explore why these perceptions matter, how they form, and if they can be changed in future work,” said the Michigan doctoral researcher.
For Thai readers striving to build strong, lasting relationships, the study offers practical lessons: focus less on finding a partner who matches every trait on your checklist, and pay more attention to fostering mutual understanding, respect, and emotional closeness. Rather than stressing over differences, it may be more fruitful to invest in the shared journey of growth and adaptation—a process celebrated in Thai proverbs such as “Nam jai hai gun” (น้ำใจให้กัน), meaning “generosity of spirit towards each other.”
For those seeking to improve or maintain their relationships, practical steps include intentionally noticing positive qualities in your partner, being open about differences, and regularly discussing shared dreams and values. Couples counseling, mindfulness practices, and community support groups—widely available in Thailand’s larger cities—can also provide tools to strengthen the emotional bonds that matter most.
As research continues, Thais may find reassurance in knowing that there is no single formula for compatibility or long-term happiness. By shifting the focus from checklist-style matching to cultivating a sense of connection, couples across the kingdom can navigate the joys and challenges of partnership, knowing that what truly matters is the sense of being “nak khon derm” (นักคนเดินร่วม), or “companions walking together on life’s path.”
For more detail and a complete view of the data, see the original review summarized by PsyPost.