"I was really having a difficult time understanding them," he says.

"I was like: 'You know what? If I'm going to be friends with her friends, and friends with her family - which I would want her to be with mine - then I'd better learn this. Because this is what they're speaking, and I don't want them to just speak Mandarin to me because I'm a foreigner. I want them to be themselves'."

With the help of friends and his ex-girlfriend, Christler began learning his third Chinese dialect - he is also familiar with the northeastern region's Dongbei vernaculars.

Mastering a new language in adulthood is tough for most people. But, with a combination of effort, good teachers and talent, it can be done, University of Hong Kong assistant professor of linguistics Picus Ding says.

Being able to speak a second language also makes learning a third easier, he says, since bilingual people are already exposed to sounds outside their native tongues.

Lawman and Christler could only speak English when they arrived in China. They disagree with the frequent suggestion they have an innate knack for language.

Back home, Lawman says he tried to learn French and Spanish, while Christler took a stab at Spanish - with no success. And yet, these languages are supposedly some of the easiest for native English speakers to learn. Then again, they weren't in love with those tongues' native speakers.

Zhang Xiaomin in Dalian and Xing Yi contributed to this report.

Related: Media breathes new life into dying dialects