What makes each person unique has long fascinated scientists and the public alike. Even identical twins, who share nearly all their DNA, can develop noticeable differences in personality, illustrating that genetic similarity does not translate into identical psychological characteristics.
Researchers have now conducted the largest genetic analysis to date of the Big Five personality traits. The international team identified more than 1,000 genetic variants associated with differences in how people tend to think, feel and behave. The findings were published in Nature.
What the huge study examined
The project was led by psychologist Ted Schwaba of Michigan State University, with co-senior authors Michel Nivard of the University of Bristol and Elliot Tucker-Drob of the University of Texas at Austin. Researchers combined data from 46 cohorts.
Some analyses included approximately 1.14 million participants who had genetic data alongside personality assessments measuring the Big Five traits: extraversion, agreeableness, conscientiousness, neuroticism and openness to experience.
Using genome-wide association studies, or GWAS, researchers scanned the genome for genetic variants associated with differences in personality scores. GWAS can identify statistical associations across very large populations but do not necessarily establish that an individual variant directly causes a particular personality characteristic.
What the genes actually reveal
The analysis identified 1,260 genetic variants associated with the Big Five traits, including 824 that had not previously been reported. Each individual variant had an extremely small association with personality.
Across the five traits, the genetic variation captured in the analyses accounted for approximately 7.4% to 10.6% of differences in personality scores. When researchers used genetic information to predict personality in independent samples, the resulting polygenic scores explained less than 4% of the variation.
These results make genetic information a poor predictor of an individual’s personality. DNA cannot reliably determine whether a particular person will be highly anxious, outgoing, agreeable or conscientious, while direct personality assessments remain considerably more informative.
Genes are only part of the picture
The relatively limited predictive power of the identified variants highlights how much of personality remains unexplained by current genetic data. Environmental experiences and other biological and developmental influences also contribute to personality differences.
To examine whether associations found between unrelated people might be distorted by factors shared within populations or families, researchers also conducted within-family analyses involving siblings.
The genetic associations observed within families were broadly consistent with those detected across unrelated individuals, strengthening confidence that the findings were not simply artifacts of population-level differences.
However, this does not mean that the study precisely separated genetic influences from every environmental influence, nor does the percentage explained by measured genetic variants directly indicate how much personality is “caused” by environment.
Why agreeableness is harder to map
Agreeableness emerged as particularly complex. Genetic associations for this trait showed greater heterogeneity across samples than those for several other personality dimensions.
Agreeableness generally encompasses characteristics such as cooperation, compassion and interpersonal warmth. However, differences in questionnaires, populations and cultural contexts can affect how the trait is measured across studies.
This variation may make genetic associations harder to reproduce consistently. Future research using more standardized and culturally diverse personality measures could help clarify these differences.
Links to health and behavior
Although genetic information cannot meaningfully reveal an individual’s personality, large datasets can help researchers investigate population-level relationships between personality and other characteristics.
The study identified genetic correlations between personality traits and a range of other outcomes. Such correlations can indicate that some genetic influences are statistically shared between two characteristics, but they do not establish that one causes the other.
For example, the researchers reported a genetic relationship involving extraversion and COVID-19 infection. However, the genetic analysis itself does not demonstrate that extraverted behavior led to greater social contact and therefore caused increased infection risk. That remains a possible behavioral interpretation rather than a conclusion established by the genetic association.
Personality has also been associated in previous research with outcomes including mental health, work-related behavior and longevity. Large genetic studies may help researchers investigate some of the biological and behavioral pathways underlying these relationships.
No genetic verdict on who you are
The findings strongly argue against using genetic results as a deterministic description of an individual’s personality. Genetic differences contribute to variation between people, but the effects of individual variants are extremely small and genetic predictions remain imprecise.
Personality itself is also not completely fixed. Research indicates that personality traits can change across the lifespan and may be influenced by development, experiences and changing circumstances.
For someone interested in understanding their own personality, validated personality assessments remain substantially more useful than consumer DNA tests. The value of these genetic findings lies primarily in studying patterns across very large populations rather than predicting the character of individual people.
The study therefore adds an important piece to the science of human individuality without providing a genetic blueprint for personality. Genes contribute to differences in personality, but they represent only one part of a much more complex combination of biological, developmental and environmental influences.
