Recent research published in Journal of Personality Research It has been suggested that long-term spouses share strong similarities in certain personality traits, particularly when it comes to honesty and openness. The findings provide evidence that while couples are generally accurate in judging each other’s personalities, they tend to believe their partner is more like them than they actually are.
Psychologists often measure human personality using structured frameworks that classify complex behaviors into broad categories. One prominent framework is the HEXACO model, which organizes human personality into six broad dimensions. These dimensions include honesty, humility, emotionality, extraversion, agreeableness, integrity, and openness to experience. Each of these broad categories includes narrower subcategories known as facets that describe specific behavioral trends.
For example, the honesty and humility dimension includes aspects such as fairness, honesty, and humility. The dimension of openness to experience includes aspects such as aesthetic appreciation, exploration, creativity, and unconventionality. Researchers use these detailed frameworks to understand how personality influences our everyday choices, including who we choose as long-term romantic partners.
In the context of romantic relationships, scientists often focus on three different statistical concepts to understand personality dynamics. The first concept is self-partner agreement. It measures how accurately a person’s evaluation of their partner matches their own self-evaluation. A high score here means the partners know each other well.
The second concept is actual similarity, which examines whether two partners truly share the same personality traits based on their own self-reports. The third concept is the assumption of similarity, which describes a person’s tendency to perceive that their partner has the same personality traits as them. The assumption of similarity occurs regardless of whether the couple actually shares those characteristics.
Previous studies examining whether spouses have similar personalities have yielded mixed results. Studies using another popular framework called the Big Five model often find little actual similarity between spouses. This tends to suggest that people don’t necessarily choose romantic partners with similar personalities, a finding that challenges the common idea that birds of a feather flock together.
However, studies using the HEXACO model sometimes find different patterns, leading researchers to investigate these dynamics in older demographics. “Research on whether social partners (friends and romantic partners) share similar personality traits has shown that partners are similar in two personality traits,” said Kibum Lee, a professor of psychology at the University of Calgary and lead author of the study. have been shown to be similar only in two traits: honesty, humility, and openness to experience, and people often overestimate this similarity, a phenomenon known as assumed similarity.”
By focusing on older adults, the authors wanted to see how longer-lasting marriages were consistent with these earlier findings. “We wanted to know whether this pattern was more pronounced among long-term spouses than among close friends or young lovers,” Lee said. “The data confirmed this prediction.”
To investigate these personality dynamics, the researchers recruited participants through a certified Dutch Internet survey panel. The final sample consisted of 451 heterosexual married or cohabiting couples from the Netherlands. This resulted in a total sample size of 902 participants.
The average age of those participating in the study was approximately 55 years, representing a mature demographic. The couples in this sample have a particularly long history. Their relationship spanned from one year to just over 64 years. On average, these couples have been together for 28 years, making them an ideal testing ground to see how well partners know each other.
Each participant completed a standard personality questionnaire known as the HEXACO-100. The survey asks individuals to rate their agreement with various statements on a five-point scale ranging from “strongly disagree” to “strongly agree.” This questionnaire reliably measures six major personality factors and 25 specific facet traits.
Participants completed the questionnaire twice during the study. First, they filled out a description of their own personal behavioral tendencies. They then completed the exact same survey again, but this time they answered the questions based on how they viewed their partner’s personality. This dual approach allowed the scientists to directly compare self-reports with their partners’ reports.
This data provides evidence of very high self-partner concordance across all measured characteristics. The statistical correlation for agreement averages about 0.70, which is significantly higher in psychological research. This suggests that people in long-term relationships are very accurate judges of their partner’s true personality traits.
Openness to experience showed the highest level of agreement among the six core traits. Spouses were especially good at identifying their partner’s level of curiosity and appreciation for art and beauty. The researchers suspect that these high concordance scores represent a practical upper limit to what paper-and-pencil personality questionnaires can measure.
Interestingly, although honesty and humility showed the lowest levels of self-partner agreement among the major traits, they were still relatively high overall. When researchers took a closer look at the specific aspects of honesty and humility, they found that spouses have difficulty accurately determining honesty and humility. On the other hand, they were much better at agreeing on their partner’s level of fairness and greed avoidance.
The authors suggest several possible reasons for this low agreement regarding honesty and humility. It is likely that individuals have difficulty determining their own humility objectively, thereby distorting initial self-reports. And internal traits such as honesty and humility may simply be difficult to accurately judge for an outside observer, even if that observer is a spouse of nearly 30 years.
When looking at actual similarities, the study found clear patterns that distinguish HEXACO traits from each other. Honesty, humility, and openness to experience were the only key characteristics that showed strong positive similarities between spouses. When one partner scored high on honesty and directness, the other partner tended to score similarly high in that particular area.
The other four main features had close to zero actual similarity. For example, an extrovert is just as likely to marry an introvert as he is to be married to another extrovert. Only some specific subtraits of extraversion, such as social self-esteem and liveliness, showed mild similarity between partners.
Findings on estimated similarity followed a similar pattern, but were generally much stronger. Spouses naturally considered themselves to be very similar in honesty, humility and openness to experience. In fact, in the case of honesty and humility, the hypothesized similarity was significantly higher than the actual similarity calculated by the researchers.
This suggests that people tend to largely project their own moral and ethical values onto their romantic partners. Since it is somewhat difficult to fully judge a partner’s inner integrity and humility, people may simply assume that their partner has the same level of integrity as they do. People who value fairness and integrity are more likely to believe that their long-term partner has those very same moral values.
The authors urge caution when interpreting what these similarities mean for individual relationships. Although shared values are common, it is not a strict requirement for a successful marriage.
“The key point is that social partners tend to be similar in honesty, humility, and openness to experience. These traits are closely related to people’s values and worldviews, and they are important for initiating and maintaining relationships,” Lee told SciPost.
At the same time, differences in personality do not necessarily lead to failure in love. Although the overall effect size observed in our data is noteworthy, it is not absolute. “However, it should be noted that this similarity is only slight,” Lee added. “There are many happy, long-lasting couples who differ greatly in these characteristics.”
The researchers also note some limitations to their findings, as well as directions for future research. The entire sample consisted of Dutch nationals, representing a very specific Western cultural background. Dating and marriage customs vary widely around the world, and these cultural differences can influence whether people choose partners with similar characteristics.
For example, a previous study conducted in mainland China found that similarity between romantic partners was nearly zero in all HEXACO traits, such as honesty and openness. Whether this discrepancy is due to differences in cultural norms surrounding marriage in collectivist societies is not fully understood. It may also be due to differences in how people in different geographical regions interpret translated survey questions.
Future research should focus on testing these personality dynamics in other non-Western cultures to see if the patterns hold globally. Scientists could also investigate exactly why certain traits, like social self-esteem, show slight similarities between couples. Sharing similar levels of self-esteem may help maintain romantic bonds. Alternatively, it may simply be that a couple’s common living circumstances affect both partners’ self-esteem equally over time.
The study, “Self/Spouse Concordance, Similarity, and Assumed Similarity in HEXACO Personality Factors,” was authored by Kibeom Lee, Michael C. Ashton, and Reinout E. de Vries.
