The researchers conclude that healthy couple friendships make a marriage more fulfilling and exciting for several reasons: By increasing partners’ attraction to each other, providing a greater understanding of the opposite sex, and allowing partners to observe ways that other couples interact and negotiate differences.

“With a great couple friendship, you get to see your partner at her/his best,” study researcher Geoffrey Greif, of the University of Maryland, told LiveScience in an email. “He/she is having fun, interacting in a loving and supportive waywith another couple as well as with the partner.”