WHEN researchers ask cohabitors these questions, partners often have different, unspoken — even unconscious — agendas. Women are more likely to view cohabitation as a step toward marriage, while men are more likely to see it as a way to test a relationship or postpone commitment, and this gender asymmetry is associated with negative interactions and lower levels of commitment even after the relationship progresses to marriage. One thing men and women do agree on, however, is that their standards for a live-in partner are lower than they are for a spouse.

Sliding into cohabitation wouldn’t be a problem if sliding out were as easy. But it isn’t. Too often, young adults enter into what they imagine will be low-cost, low-risk living situations only to find themselves unable to get out months, even years, later. It’s like signing up for a credit card with 0 percent interest. At the end of 12 months when the interest goes up to 23 percent you feel stuck because your balance is too high to pay off. In fact, cohabitation can be exactly like that. In behavioral economics, it’s called consumer lock-in.

Lock-in is the decreased likelihood to search for, or change to, another option once an investment in something has been made. The greater the setup costs, the less likely we are to move to another, even better, situation, especially when faced with switching costs, or the time, money and effort it requires to make a change.

Cohabitation is loaded with setup and switching costs. Living together can be fun and economical, and the setup costs are subtly woven in. After years of living among roommates’ junky old stuff, couples happily split the rent on a nice one-bedroom apartment. They share wireless and pets and enjoy shopping for new furniture together. Later, these setup and switching costs have an impact on how likely they are to leave.

Jennifer said she never really felt that her boyfriend was committed to her. “I felt like I was on this multiyear, never-ending audition to be his wife,” she said. “We had all this furniture. We had our dogs and all the same friends. It just made it really, really difficult to break up. Then it was like we got married because we were living together once we got into our 30s.”

I’ve had other clients who also wish they hadn’t sunk years of their 20s into relationships that would have lasted only months had they not been living together. Others want to feel committed to their partners, yet they are confused about whether they have consciously chosen their mates. Founding relationships on convenience or ambiguity can interfere with the process of claiming the people we love. A life built on top of “maybe you’ll do” simply may not feel as dedicated as a life built on top of the “we do” of commitment or marriage.

The unfavorable connection between cohabitation and divorce does seem to be lessening, however, according to a report released last month by the Department of Health and Human Services. More good news is that a 2010 survey by the Pew Research Center found that nearly two-thirds of Americans saw cohabitation as a step toward marriage.