Study reveals only 9 to 18% of personality is written in your DNA

In 2009, a defence lawyer in Trieste, Italy, successfully argued that his client's possession of the so-called "warrior gene", a variant of the MAOA gene linked to aggressive behaviour, should reduce a murder sentence by a full year. The argument worked. The science, it turns out, did not hold up nearly as well.

Researchers established a connection between the MAOA gene variant and violent behaviour after the 1990s, which the media subsequently reported. But Aysu Okbay, assistant professor of psychiatry and complex trait genetics at Amsterdam UMC in the Netherlands, says the entire premise of single-gene explanations for behaviour has since collapsed.

"People believed that behaviours result from a few genes which have major impacts," she states. "The entire concept has been proven to be incorrect."

Current research shows that personality develops through multiple genetic factors which include thousands of genetic variants that each produce imperceptible effects. A 2015 meta-analysis of more than 2,500 twin studies covering nearly 18,000 human traits found that genetic differences account for roughly 47% of personality variation.

The Big Five personality traits of openness, conscientiousness, extraversion, agreeableness, and neuroticism show only 9 to 18% heritability according to genome-wide association studies that analyse millions of tiny genetic variations across the entire genome.

The research shows that humans possess less genetic potential than scientists originally believed, so scientists must now explore which environmental elements, including life events and social interactions and life situations, create the missing genetic potential.

The research repeatedly delivers unexpected results to Professor Brent Roberts, who teaches psychology at the University of Illinois at Urbana-Champaign.

He explains that major adult traumatic events create only mild psychological effects which will not result in significant long-term consequences. People experience no significant personality changes from marriage or divorce or financial windfalls because these events function as individual elements that affect their core personality traits.