Why are some people more outgoing than others? Why do some individuals tend to be more anxious, while others are able to remain calm under pressure? Personality has long been studied as a product of both biology and experience, with researchers having long known that personality has a genetic component. However, actually identifying the specific genetic variants responsible has been difficult because personality is a highly complex trait. There is not one person on Earth who has the same exact personality as another.

Researchers from the Revived Genomics of Personality Consortium, an international collaboration coordinated by Michigan State University, conducted one of the largest genetic studies of personality to date, involving more than one million people and identifying approximately 1,200 genetic variants associated with personality traits. Using the famous “Big Five” personality framework, the findings of this research provide new insights into the biological foundations of human behavior. The Big Five model describes personality across five major dimensions: openness, conscientiousness, extraversion, agreeableness, and neuroticism. This model of personality works especially well because instead of putting people into fixed categories, these traits exist on a spectrum. For example, a person can be relatively introverted but still enjoy social situations, whereas another person can be highly conscientious but struggle with organization in different environments.

The new study demonstrates just how complicated genetic architecture is. Instead of being controlled by a handful of genes, personality appears to be influenced by thousands of genetic differences, and each variant contributes only a small effect. It also highlights the limitations of genetic prediction, because even when researchers identify numerous genetic variants associated with a trait, those variants explain only part of the differences observed between individuals. Environmental experiences and other biological factors remain essential and make up the remainder of what determines someone’s overall personality.

Ultimately, personality cannot be reduced to a DNA sequence. Our genes may influence tendencies in how we think, feel, and behave, but those tendencies develop within the environments we experience. This recent study evaluated genetic variations in connection to the Big Five traits, but these are only a few facets of personality. Scientists agree that there is not one gene connected to personality, but instead a combination of complex genetic interactions, environmental factors, and development.