“Regarding the use of the L1 to teach the L2, I’ve done a fair bit of work on this one myself, and I tend to agree with your conclusion that the L1 does have a place in the classroom. Probably the only reason it doesn’t have MORE of a presence is because to make it an essential teaching skill would force a lot of native English teachers to actually get off their butts and learn the language of their host country.
In researching the last bit of work I did on this subject, it became clear that while there is an abundance of evidence in support of using the L1 in class (but within a communicative framework — not grammar translation), there is NO evidence in favour of the English Only paradigm. Everything out there really amounts to little more than personal arguments of why people should not use the L1. But there is no classroom based, experimental evidence.
I’ve published a few papers on this, and in 3 largish presentations at international conferences, I’ve offered $100 to anybody who can go home and find a valid, experimental study putting English Only vs L1 support head to head, with English Only winning. So far, nobody has claimed the $100. And I doubt they ever will. ” (Peter McKenzie-Brown, “Language Matters”, Email 2006; see Peter McKenzie-Brown’s article „Using the mother tongue to teach another tongue“ 2006.)