Peter Behr and Gus Tate are both from the United States, and both speak English. Behr attends university in Chicago; Tate was born there. They are both 21 years old, and for eight weeks this summer, the two were roommates in Beijing.
Despite the similarities, Behr and Tate's friendship is based entirely in Chinese. Other than the odd word and phrase peppered into conversation here and there, they have not spoken English to each other since they first met two months ago.

Nor are they speaking English to me as I interview them at a Cantonese restaurant near Beijing Normal University, where Behr and Tate are in the final week of Princeton University's intensive Chinese language program, called "Princeton in Beijing".

Students enrolled in the 15-year-old "total immersion" course must pledge to speak no other language than Chinese for the duration of the eight-week, two-semester program, at risk of being expelled.

Because they've sworn off English, and I can't speak Chinese, Chen Yuwang, a China Daily intern and journalism student at Peking University, acted as translator.

The irony is hard to miss.

Do Behr and Tate ever feel trapped, or unable to fully express themselves? Does it ever feel like their heads are about to explode?

"It does get lonely," Behr says through Chen. "But we're all in the same boat. The promise to not to speak your native language is the most important aspect of the program. But, of course, it's difficult."

There are 167 students in the program, ranging from second to fifth years students. They come from the United States, Europe, Japan, South Korea and elsewhere, and most are students from Princeton University. To apply, students had to submit a pronunciation tape, and a statement of purpose and essay written in Chinese.

The $4,500 course consists of four hours of classroom time per day, plus a one-hour, one-on-one session with a professor. Twice a week they have lunch with their professors when they discuss everything from academics to favorite films.

The program's main feature is the language pledge. Other than when speaking with family, students must swear off their native tongue.

For many of us who use the English language every hour of the day, it may be hard to wrap our heads around the idea of speaking only Chinese for two months. Behr studied Chinese for the first time in the summer of 2006 in Shanghai, and has since taken a few classes at the University of Chicago, where he majors in math.

Tate, entering his senior year studying computer science at Princeton, has taken Chinese classes for the past two years. But neither student was anywhere near fluent when the program began.

Sometimes, students in the program feel the need to vent in their native tongues. On a few occasions, students let loose in English after a few beers at Beijing bars - a violation of the program's rules. On other occasions, students allow the language floodgates to open when speaking with family members over the phone.

"My brother, who is in France, called, and we talked for an hour and a half. It's nice when you get the opportunity to talk totally freely, instead of just sort-of freely," Behr says.

The language pledge isn't easy, and sometimes, students have to break the rules - or at least bend them.

Sporadically during our conversation, Behr sneaks in English words and phrases to me to explain something he's said in Chinese. He does it quietly, under his breath, as if worried of being caught. Students can be kicked out from the Princeton program for speaking their native language; several received warnings this year.

"Sometimes I put English words into sentences so people know what I mean," Tate admits.

Behr and Tate worry that they sometimes come off as rude to other foreigners, with whom they can't really communicate unless in Chinese.

"Sometimes it's impolite. They don't know Chinese, or you insist and they feel uncomfortable," Behr says. "But if I'm speaking to somebody and I know they speak Chinese, I'll just keep speaking Chinese."

They've also had to shun a few local Beijingers who approach the two Americans hoping to practice English.

"On the street I'll run into Chinese people who want to practice their English, and I say, 'Sorry, it's not the time'," Tate says.

Mostly, the students have stuck to the rules. Behr and Tate swear that at night hanging out in their dorm room, away from the discerning eyes of program administrators, they communicate in Chinese.

And both say the program is well-worth it - especially the language pledge. They feel they'll come out with a better understanding of Chinese language and culture than if they'd enrolled in a competing program. "Knowing Chinese is another strength for getting a job. It also provides a new understanding of the culture and lifestyle," Tate says.

As for the language, they are that much closer to fluency - though both say learning Chinese is a lifetime commitment.

"Sometimes I stumble over a word," Behr says. "But generally speaking, we are fluent."