“They found that for Chinese immigrants, addressing a Chinese face increased social comfort but reduced English fluency. “It’s ironic” that the more comfortable volunteers were with their conversational partner, the less fluent they became, Zhang says.”
“Reminders of home can disrupt your ability to process a foreign language”
I totally believe this, and suspect that’s what they’d really like to prove. I don’t really like the actual experiment they did, but I suppose it’s a step in the right direction.
The study is flawed. It equates situational fluency with actual fluency. It may be a useful distinction for planning social occasions and outcomes assessment, but regardless they are not the same. Although I suspect it is merely the phrasing used in the casual summary of the study. Basically, they found that situation influences expressive tendency. Around their own kind, a non-native speaker will make more of what would be considered mistakes.