The key to relationship happiness could be as simple as finding a nice person.

And, despite popular belief, sharing similar personalities may not be as important as most people think, according to new research from Michigan State University.

“People invest a lot in finding someone who’s compatible, but our research says that may not be the end all be all,” said Bill Chopik, associate professor of psychology and director of MSU’s Close Relationships Lab. “Instead, people may want to ask, ‘Are they a nice person?’ ‘Do they have a lot of anxiety?’ Those things matter way more than the fact that two people are introverts and end up together.”

The most striking finding of the study was that having similar personalities had almost no effect on how satisfied people were in their lives and relationships, Chopik said.

So, what does this research mean for dating apps?

Despite their popularity, apps that match people on compatibility may have it all wrong, he said.

“When you start to get into creating algorithms and psychologically matching people, we actually don’t know as much about that as we think we do,” Chopik said. “We don’t know why the heart chooses what it does, but with this research, we can rule out compatibility as the lone factor.”

The researchers looked at almost every way couples could be happy, making it the most comprehensive study to date.

Using data from the Panel Study of Income Dynamics, which is a long-running survey of households, Chopik and Richard Lucas, MSU Foundation Professor in the Department of Psychology, measured the effects of personality traits on well-being in more than 2,500 heterosexual couples who have been married roughly 20 years.

Even among the couples who share similar personalities, Chopik and Lucas found having a partner who is conscientious and nice leads to higher levels of relationship satisfaction. At the same time, having a partner who is neurotic, and, surprisingly, more extroverted, results in lower relationship satisfaction.

The study is published in the Journal of Research in Personality.

(Note to media: Please include a link to the original paper in online coverage: https://www.sciencedirect.com/science/article/pii/S0092656618301508)