Newswise — While the value of friendship has been well established for individuals, little had been known about the impact of married couples’ forming and keeping friendships with other couples. These relationships often make for happier marriages and also improve the bonds between adults who are unmarried partners, concludes a new book, “Two Plus Two: Couples and Their Couple Friendships,” (Routledge, 2012).

Co-authors Geoffrey Greif, DSW, MSW, professor at the University of Maryland School of Social Work, and Kathleen Holtz Deal, PhD, MSW, associate professor at the School, have found that when couples agree on how they spend their time alone and with others, they are more likely to have a happy marriage or relationship. The book offers language that couples can use to talk with each other to find a balance that works for them.

The findings are based on interviews with 123 couples with both partners present, 122 individuals who were alone when questioned about their relationships, and 58 divorced individuals. To identify and interview subjects for the study, the professors began with the work of 58 master's students in an advanced research course and then interviewed more than 20 couples themselves. The stories of these couples, who remain anonymous, are highlighted in the book.

The research found differing motivations behind couples’ friendships, with some people preferring to share emotions while others see the purpose as fun and recreation. The ways the friendships get started also vary, with the majority growing out of a typical friendship between two people that widens to encompass all four. Say the men were pals are work, or the women met at college and decided to see if their spouses might get along, too.

Deal, who has been married 43 years, says she was surprised to find that she and her husband were in the minority because they set out as a pair to make friends with other couples. They established friendships with a group of five other couples that have lasted for over 30 years. They have shared social events and vacations. “We can talk about anything we want to. We have shared sad times, and good times,” she says, calling the group of friends, who met one another at church, “a huge influence on my life.”

Greif says that he and his wife of 36 years “feel very comfortable” in their friendships with other couples and that work on the book has given him the “language to think about how couple friendships are begun and how they are maintained.”

As the author of articles and books on family issues, Greif had previously studied men and their interactions for his 2009 book, “Buddy System: Understanding Male Friendships.” He says a look at friendships among married adults seemed a logical next step. From the outset of the project over three years ago, the co-authors found very little had been written. “Regarding adult long-term relationships across the lifespan, this is it,” says Greif.

Greif and Deal conclude that healthy couple friendships make a marriage more fulfilling and exciting for several reasons, such as increasing partners’ attraction to each other, providing a greater understanding of men and women in general, and allowing partners to observe ways that other couples interact with each other and negotiate differences. However, they found that the topics of sex and money continue to be taboo even among friends.

Couples fall into one of three categories, according to how they approach their friendships with others, the research shows. Readers can ask their partners which one best fits their own profile as a twosome. Seekers? Keepers? Or Nesters? Greif and Deal describe seekers as extroverts who are often looking for another couple with whom to socialize. Keepers have full lives and many friends, and are not necessarily looking for more. Nesters tend to be introverts who have a small number of couple friends and are content with that.

Compromise is required when an introvert marries an extrovert, and a couple’s outlook may change as life stages do. The content of “Two Plus Two” is organized across the lifespan, with chapters including, “The Middle Years: Couples Raising Families and Balancing Friendships,” and “Older Couples and Their Couple Friendships.” The oldest couples are now in their eighties and nineties.

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Two Plus Two: Couples and their Couple Friendships (2012)