Researchers did the largest analysis ever on how similar spouses and partners are for different traits.
They found that partners tend to be positively correlated, meaning they are more alike than random pairs of people.
However, how much partners resemble each other differs a lot depending on the trait.
Additionally, they saw that couples from different cultures and time periods vary a lot in their similarities.
Key Facts:
- Partners were analyzed for 22 traits through combining data across nearly 500 past studies involving over 2 million couples total.
- Partners resembled each other the most for political views, religion, education level, intelligence, and smoking behaviors. They matched the least for personality traits like extraversion and emotional stability.
- There was a very wide range in how similar partners were across the nearly 500 studies. This means couples’ resemblances differ a lot across cultures and eras.
- Separately, researchers looked at partner similarity for 133 traits in a sample of 79,000 middle-aged British couples. The patterns were fairly similar to the meta-analysis.
Source: Nature Human Behavior 2023 Aug 31.
Who Were the Couples Studied?
The researchers gathered data from nearly 500 past studies on partner similarity published over the last century.
In total, the studies included over 2 million couples from countries across the world, though most were from the United States and Europe.
The couples were either married, cohabitating, or raising children together.
The researchers did meta-analyses to statistically combine all the data on similarity for each of the 22 traits.
In a separate analysis, the researchers looked at partner resemblance for 133 traits in 79,074 middle-aged couples from the United Kingdom Biobank.
This sample was mostly white Europeans. These couples lived together and were married or in long-term partnerships.
What Traits Showed the Most and Least Similarity Between Partners?
Partners showed the most similarity for traits related to:
- Political values – how liberal or conservative their social and fiscal political attitudes were
- Religion – how important religion was to them
- Educational level – their highest academic degree obtained
- IQ score – their intelligence test scores
- Smoking – whether they smoked and how many cigarettes per day
Meanwhile, partners showed the least resemblance for traits related to:
- Extroversion – how outgoing, enthusiastic, and socially confident they were
- Emotional stability – how anxious, irritable, and moody they were
- Agreeableness – how kind, cooperative, and trusting they were
In the British couples, researchers also found larger similarity for overall life satisfaction and financial satisfaction compared to satisfaction with one’s health or job.
Partners’ ages and the ages they first had sex were also fairly similar.
Why Are Partners Similar?
There are several reasons why partners may end up resembling each other:
Assortative mating: Partners may be initially attracted to and choose people similar to themselves. This can involve actively looking for similarities or indirectly choosing partners from one’s same social circles.
- For example, a highly religious person may want to date someone else who is religious. They may join groups and events where they are likely to meet like-minded partners.
Convergence: Partners may become more alike over time through directly or indirectly influencing each other.
- For instance, one outgoing partner may pull their shyer partner out of their shell. Or partners may take up each other’s hobbies and adopt similar mannerisms through living together.
Shared environment: Partners are shaped by the same external factors after they get together, beyond their direct influences on each other.
- Going through major life events together like having kids or stressful times can make partners’ personalities, attitudes, and health more alike.
Genetics: Partners may not be similar for a trait itself but for genetically-influenced traits associated with it.
- For example, religiosity and political attitudes are shaped by many genes that affect personality. So genetic similarity for personality can make partners act alike religiously and politically without any direct similarity in those traits.
Why Do Some Traits Show More Similarity Than Others?
The researchers found a clear pattern in which traits tended to show the most and least partner similarity.
Attitudes, behaviors, and preferences people consciously think about showed the most similarity between partners.
Meanwhile, more biologically-influenced traits like personality and body shape showed less similarity.
There are several possible reasons for these differences:
- People likely actively look for partners who share their values on things like religion and politics. But personality is largely genetic, so people do not actively choose partners based on introversion or anxiety levels.
- Attitudes and behaviors can directly converge between partners. But traits like height and intelligence are mostly stable, so couples do not become more similar on them.
- Shared views between partners on abstract things like politics may better signify relationship compatibility compared to shared body mass index or cholesterol levels.
- People may have more awareness of how their personality compares to a potential partner’s than their respective cholesterol levels or risk of diabetes. Thus, partners may be more likely to implicitly “match” on personality similarity.
What are the main takeaways from this research?
The main conclusions from this large research synthesis are:
- Partners tend to be more alike than random pairs of people for almost all traits studied, though the magnitude varies greatly across traits.
- Attitudes, behaviors, and preferences show the most similarity between partners, while biological traits show less.
- There is huge variability between cultures and eras in how much partners actually resemble each other on a given trait. So findings may not generalize across all human populations and time periods.
This massive analysis helps provide an updated picture of patterns and variability in human partner similarity.
These discoveries can help researchers better understand the origins of similarities between partners.
They also aid genetic studies on humans by quantifying potential biases.
References
- Study: Evidence of correlations between human partners based on systematic reviews and meta-analyses of 22 traits and UK Biobank analysis of 133 traits
- Authors: Tanya B Horowitz et al. (2023)
