College students rarely spend time on official "dates" anymore.

The fast-paced and flighty "hook-up" culture has come to define the nature of most romantic interactions on campus.

Kathleen Bogle, assistant professor of sociology and criminal justice at La Salle University in Philadelphia, examines the complex term "hook up" and the social movement it signifies in her book "Hooking Up: Sex, Dating, and Relationships on Campus" (New York University Press).

The term hooked up indicates some degree of physical intimacy between a couple, but the level of that intimacy is left to the listener's imagination.

"One of the biggest mistakes the public makes is assuming that it only means sex," Dr. Bogle said. "By no means is that true. It can mean anything from just kissing to intercourse ... really anything on the sexual spectrum."

In the hook-up culture, physical involvement always precedes an emotional relationship, if the latter develops at all. Hooking up is seen as the desirable end to a night of socializing in mixed-gender company, often within a party atmosphere. As Dr. Bogle described in her book, partners usually meet and talk in a group setting and then pair off to become intimate at the end of the night.

"I think it's a big part of college life," said Joe, 19, a sophomore at Duquesne University. "Sexual desire is a big factor and so is freedom ... people want to get into that culture for the freedom of it." (Students agreed to speak for this article on the condition that their last names be withheld.)

The ambiguous definition of the term hook up makes it popular with males and females alike, says Dr. Bogle. Males can boast about hooking up with a girl while females can use it without appearing undesirably promiscuous.

"It's only acceptable for really close friends to ask, 'How far did you guys go?' " she said.

James Cox, director of the counseling center at the University of Pittsburgh, believes a new sense of casualness about dating not prevalent in earlier generations has led to the decline of committed relationships on campus.

"It's more of a societal thing than a college thing," he said, noting that about 20 percent to 30 percent of students in the counseling center come in with romantic concerns. "There's been a relaxing of morals -- it's more acceptable for couples to live together, so students feel less pressure to get married."

Brenden, a 21-year-old Duquesne University senior, believes that college students are generally too consumed with self-discovery to pursue committed relationships.

"College is when you figure out what to do with your life, and things become muddled if you try to mix your life with someone else's," said Brenden, of the South Side. "I don't know where I'll be five years [from now] or where 75 percent of my friends will be. It's impractical to start a [serious] relationship like that."

Hook ups can develop into emotionally invested relationships, but that's far from guaranteed. Most students know that hooking up doesn't usually lead to "going steady" or "getting pinned."

Students can encounter emotional difficulty, however, when one partner seeks relationship exclusivity while the other does not -- a situation especially common when partners meet to hook up multiple times. One partner may begin to think of the other as that special someone, but the feeling may not be reciprocated.

Women often are the ones who view hook-ups as an avenue to finding relationships and often pursue them for that purpose, Dr. Bogle said. Her research found that when two partners hook up repeatedly, it usually means the woman wants a relationship but not necessarily the man.

Men uninterested in commitment may continue to hook up with the same woman because he finds her physically attractive and feels it is more convenient to keep the same partner than to spend time and energy finding a new one, she said.

Such ambiguity on the men's part prompts women to initiate discussions about an official relationship. "Women are more likely to give men 'the talk' and ask, 'Can I introduce you as my boyfriend now?' " Dr. Bogle said.

She attributes this trend partially to the fact that most college women aspire to marry sooner than their male counterparts, and they now tend to outnumber men on campuses.

"Most of the women I interviewed said they wanted to marry no later than a certain age, but most men said they would marry no sooner than a certain age," she said.

"Also, when there weren't as many women in college, men had to go out of their way to secure them for dates. Now we see just the opposite. Many girls I interviewed said there weren't enough guys -- or enough attractive guys -- on campus."

Mr. Cox, however, prefers not to classify hook-up attitudes according to gender.

"Some of the young men I work with are looking for serious relationships and want to settle down, and some young women like to party just as much as men," he said. "So it's a challenge for both sides."

Because marriage is often delayed much longer than in the past, the hook-up mentality can extend beyond college for some young adults -- namely those who aren't in a rush to tie the knot. As Mr. Cox observed, "It may happen more frequently at earlier ages, but it does happen at bars with older adults, too."

Dr. Bogle, however, found that the college atmosphere is especially conducive to the hook-up culture. Most of her interview subjects were much more hesitant to hook up in "real world" scenarios outside their campus comfort zone.

"People are raised with a fear of strangers, but college nullifies that fear -- almost everyone is between the ages of 18-22, and comes from a similar [socioeconomic] background," she said.

Hooking up after college, she explained, is much more complicated and doing so with a stranger in a bar presents new risks as well as transportation issues. No longer can students meet up, hook up, and then walk home to their dorm or apartment afterward in five minutes.

"In college there's a sense of camaraderie -- everyone feels like a friend of a friend," said Dr. Bogle. "It's ironic, though, because college campuses have high rape rates."

Jenny, 20, a senior at Duquesne University from Beaver County, said that she and her "inner circle of friends" choose not to hook up even though it is a big part of college life.

"I wouldn't go out looking to hook up with somebody," she said. "I wouldn't want to be with someone who's only looking to have a good time."

Now in a five-month committed relationship, Jenny met her boyfriend through an on-campus extracurricular activity. She knows, however, that many of her peers aren't so lucky. "I feel like I'm in the lesser portion," she said. "I think you're surrounded by that culture."

Mr. Cox encourages students to follow Jenny's example and look for long-term partners in places where common interests are shared.

"[Hooking up] is like any other kind of peer pressure," he said. "We need to encourage students to make independent, healthy choices that will serve them well. I think it's [untrue] that 'everybody's doing it.' You can look elsewhere and find people who don't engage in that behavior."