One of my students just returned from a trip to England where she was lucky enough to experience the charm and beauty of some of the small villages within reach of London via public transportation. She brought back pictures that made me ache for home because the expansive and richly green farms, fields, and trees reminded me of Pennsylvania. She also brought me back a box of Cornish Fairings which are incredibly good. I must say that I've rarely had a bad or mundane pre-packaged cookie made in England and the vast majority of "biscuits" I've had from there seem to be perfect blends of flavor, sweetness, and just the right texture. If bad cookies are being made there, they aren't finding their way to Japanese shops or into the hands of souvenir-distributing students.
Getting back to the topic at hand though, which is my student's trip, she told me that she went with a friend and her sister. I asked her if either of them spoke English as well as her and she said that her friend hardly speaks it at all but her sister's ability is superior to hers. My student is no slouch in terms of her English abilities so I asked her why she had this impression of her sister. She said that, when they engaged in casual conversations with strangers in England, her sister always responded readily and fully while she felt rather uncertain about whether or not she fully understood the question.
My student said that she couldn't figure out how her sister managed to develop such talents because she hasn't studied for quite some time and her only English study experience was while studying for university entrance exams. While it's possible that her sister has a knack for languages and just took to English like a house on fire, it's also possible that her sister is simply offering an illusion of fluency that my student is unable to detect.
In part because I didn't want my student to feel inferior to her sister (or anyone else), I decided to tell her about a well-known fact among English teachers who work in Japan. The truth is that it is possible for a student to jabber on in a fashion which makes them appear quite conversant in a language to those who don't natively speak it when they really aren't understanding the question properly at all or giving an appropriate answer. Such people usually guess at the nature of a question based on various key words and then charge ahead with a long-winded reply which completely missed the gist of the question. I can't tell you how many times I've said "tell me about your company's business" and gotten the answer "I work in (accounting/sales/research)." The student hears "your" and "business" and ignores the rest.
This particular problem is probably more common among Japanese people because they often experience teachers who aren't fluent (Japanese teachers of English in their pre-college years) or who are native speakers of English who are more interested in entertainment than in improving their students' skills. A lot of teachers never insist that a student answer a question correctly or explain the nature of their misunderstanding. They just smile and pretend the answer was right and carry on. This is essentially the same thing that a stranger you'd meet on a train in London would do if a question he's asked is answered in an energetic but incorrect fashion. Natives who strike up conversations with tourists are unlikely in the extreme to do something that will embarrass the person to whom they're speaking.
While I have no way of knowing for sure, I'm pretty sure that my student's sister was giving the illusion of fluency she does not truly possess and my student, who can't judge the English skills of others just as she cannot correct her own mistakes, couldn't tell the difference.
Incidentally, and tangentially-related to this story, my student told me that a nice young British fellow on a sleeper train they were on who struck up a conversation with these three obviously Asian young women broke the ice with "are you French?" She said that one of her friends was carrying a shopping bag from a famous French bakery but she was still baffled that he'd conclude from the bag that they might be French. It's my guess that he knew they were not but didn't want to guess at their nationality for fear of offending them should he guess wrong. While some Japanese people think they can distinguish between Koreans, Chinese, Japanese, etc., just by looking at their faces most of us westerners can't make such distinctions.