The young woman seated next to us at the sushi bar exuded a vaguely exotic air; her looks and style, we thought, made it likely that she was not American born.

But then she spoke in perfect American English, even ending her declarative sentences in that rising questioning lilt characteristic of many young Californians.

As it turns out, however, she wasn’t from these parts after all; she was born in Iran and spoke only Farsi until her arrival here two years ago. What classes, we wondered, had she attended to learn the language so well?

“I didn’t,” she said. “I used RosettaStone.”

Those yellow boxes sold at shopping-mall and airport kiosks may be the most recognizable example of PC-based language learning, but it certainly isn’t the only one.