After six years of dating, and one year engaged, Carol, 41, of Winter Park, Fla., felt something was off with her fiance. She noticed his Facebook profile had a thorough recounting of his life but didn't mention her. She also noticed he had a new female Facebook friend from the Florida Keys, where he had recently gone on vacation while she stayed home — a house they owned together — to plan their wedding.
When Carol (whose surname is being withheld) expressed her concerns, he said he wasn't sure he wanted to get married, she said. So she gave him back the ring and told him to ask when he was ready.
That didn't make it any less painful when, later that month, she said, she snooped in his email and saw a long message from the aforementioned Facebook friend describing a sexual relationship that had turned emotional.
"My world was just rocked," Carol said. "I felt that I had lost my whole purpose."
No vows need be exchanged for cheating to devastate people who believe themselves to be in committed relationships, a steadily growing demographic as couples put marriage off longer or decide they don't need a wedding at all.
Forty-eight percent of women cohabited with a partner as a first union in 2006 to 2010, compared with 34 percent in 1995, and more unmarried couples are having children, according to a report this year from the Centers for Disease Control and Prevention.
Without formal legal ties, conventional wisdom would suggest it's easier to bail after infidelity tears through the trust and intimacy that hold a couple together.
And sometimes it is. But rarely is the post-affair path clear-cut.
The limited research that exists on committed but unmarried couples suggests infidelity in those relationships is slightly more common and accepted than in marriage. A study published this year by University of Denver researchers in the Journal of Sex Research followed a nationally representative sample of 993 unmarried individuals in committed opposite-sex relationships to explore predictors of first-time infidelity. It found that 14 percent had "sexual relations" outside of the relationship over a 20-month period, and 43 percent of those broke up after the infidelity.
People who cheated were most likely to have: parents who never married; problematic alcohol use; more prior sexual partners; lower relationship satisfaction; higher levels of negative communication or psychological or physical aggression in the relationship; lower dedication or no plans to marry the partner; and greater suspicion that the other partner was cheating. Notably, the frequency or quality of the couple's sex life did not raise the risk of infidelity, nor did cohabitation decrease it.
More research explores cheating within marriage, which has become less tolerated in society.
Eighty-one percent of people of all marital statuses polled in 2012 said extramarital sex is always wrong, up from an average of 70.5 percent of people who said so in 1973 to 1980, according to the National Opinion Research Center's General Social Survey, a widely used sociological poll based at the University of Chicago. A Gallup poll earlier this year found that marital infidelity was at the bottom of the list of morally acceptable behaviors — lower than human cloning, polygamy and suicide — with 91 percent of respondents considering it morally wrong.
Yet the prevalence of cheating among married couples hasn't budged much. About 19 percent of men and 12.3 percent of women in 2012 said they'd had sex with someone other than their spouse while married, about the same as it was 20 years ago (though there's been considerable variability year to year), according to the General Social Survey. That's likely an underestimate given the reluctance of people to admit to affairs and the survey's narrow definition of infidelity as sex.
Infidelity wreaks havoc whether you're married or not. But for unmarried committed couples, there often is a difference in reasons for and consequences of an affair.
"If there's less to lose, there's a greater chance that somebody will stray from that relationship," said Dr. Scott Haltzman, a psychiatrist and author of "The Secrets of Surviving Infidelity" (Johns Hopkins University Press), released this year. "And in part, layered in the decision to be a couple but not marry is the possibility and the openness to seek relationships elsewhere."
To be sure, there are many unmarried couples who are just as or more committed than their married counterparts and have just as much or more to lose, particularly if they have children or have mingled their finances.
But Haltzman said the lack of a ring often signals that people are still in an experimentation phase of the relationship and keeping their options open. When unmarried couples get in ruts, cheating can be a way of forcing the hand.
Just because someone begins to play the field doesn't spell the death of the relationship, Haltzman said. While partners should hold each other accountable when there are expectations of exclusivity, a lapse can open a conversation about where the couple wants to go and how to define the relationship, he said.
Blake Sharpe, 25, of Washington, D.C., said she has cheated in two different serious relationships, admittedly immature reactions to monotony or feeling that she was being mistreated.
Also, she said, "it's a fear of missing out. Even if you have something good, you still want to feel needed or wanted by other people, and that probably comes from some insecurity."
Melissa Richman, a psychologist and social worker based in Los Angeles, reminds couples that monogamy is difficult and that "a committed relationship is a friendship, and there's a journey in there."
But while she urges forgiveness, she also bemoans a society in which people assume they should always get what they want.
Sometimes relationships, in marriage or outside it, shouldn't be salvaged post-cheating. A long-term affair that involved many years of deceit can stink of such disrespect that it's hard to bounce back, Haltzman said. He also cautions against returning to cheaters who have serial affairs or continue to see other people as the primary relationship grows closer.
But if the cheating partner is willing to offer complete transparency and work hard to earn back trust, it can be worth giving it another shot.
Victoria, 52, is trying to rebuild her relationship after she found out that her boyfriend of five years had been having an ongoing affair for three years.
"What is making me want to try is his actions, his tears," said Victoria, who asked that her last name and location not be used. "Things have come out during therapy: his inability to communicate and how he felt in the relationship, as though I wasn't committed to him."
The fallout from the cheating, which took place during his lunch hour with a woman he met online, was devastating.
"During one of our discussions, I got up and took every picture of us in our house and smashed them on the ground," Victoria said.
Couples and individual therapy have helped her and her boyfriend identify the underlying problems that led him to stray — including, ironically, her reluctance to get married, which left him feeling insecure, she said. His eagerness to address his issues, reveal any detail she requests and do anything it takes to make her feel safe, plus her examination of her own behaviors that might have left him feeling disconnected and lonely, have made Victoria optimistic that they can get through it.
It worked out differently for Carol and her former fiance in Florida.
She said she forgave her fiance's vacation romance too easily at first because she couldn't let the relationship go. But, she said, when she found hints that he was continuing to see other women, she felt herself become unhinged. She said she broke up with him but would obsessively check his new girlfriend's social media accounts. A few confrontations led him to pursue a restraining order against her, she added. Acrimony over money led to their house going into foreclosure, and she declared bankruptcy.
More than two years later, Carol feels she dodged a bullet but was scarred.
"I tell people I wasn't married," she said, "but I got divorced."
Before you decide
Rather than rush to save or end a relationship after discovering infidelity, couples should take time to understand why it happened and ask What is it about this person that is good for me? Clinical psychologist Janis Abrahms Spring, author of "After the Affair" (William Morrow), offers tips for rebuilding a relationship.
Write apology letters. After the hurt partner "talks about their hurt with an open heart," the cheating partner should write a letter spelling out exactly what he or she is sorry for. And vice versa. Letters are important because they demand more thought, and often people want to read the words over and over.
Engage in trust-building behaviors. That could mean the cheating partner hands over cellphone records or promises to reveal immediately if the affair partner gets in touch. "Trust and forgiveness are not gifts from the hurt partner," Spring said. "They must be earned."
Filter the discussion. It's tempting to ask for every gory detail, but consider if that's helpful, or reframe the question to be about the couple rather than the third party. Be careful not to go on and on, which can alienate the unfaithful partner and deter conversation. The best way to communicate is to speak genuinely, honestly and briefly, with the listener mirroring back what was said, so he or she feels heard.