Chopik and his team claim to have conducted the most comprehensive study ever on relationship happiness. More specifically, researchers utilized a long-term survey of more than 2,500 heterosexual couples who have been married around 20 years. Using this data, the study’s authors measured the impact of personality traits on well-being in these relationships.

Researchers were shocked when their results indicated that shared interests and similar personalities had little to no effect on relationship satisfaction. Even among couples sharing personality traits, the study found that having a conscientious and nice partner leads to a more satisfying relationship. The study also concluded that relationships including a person who is especially neurotic, or extroverted, leads to lower relationship satisfaction.