No, it's not the name of a new movie. This is one of those things second language acquisition researchers worry about and which has a significant implications for the way we teach languages. What is it?
Back in 1981-ish Stephen Krashen reworked a very old idea about language learning, namely that there are two ways we learn, the first conscious, the second unconscious. This is sometimes called in psychology explicit and implicit learning. Krashen decided to rechristen them learning and acquisition. Since then, brain research has suggested that there is a lot in this and that the brain has two quite distinct ways of processing new information, the first when we pay conscious attention, the second when information is absorbed "beneath the radar", by osmosis (for want of a better word).
Krashen went further though. He hypothesised that consciously, explicitly learned knowledge could not become part of the unconscious, implicit system. In other words, he argued, there is absolutely no interface between learned knowledge and the acquired system. This is now known in the literature as the non interface position or strong non-interface position.
Most teachers might feel this goes against what we assume and that what we focus attention on and practise can gradually become internalised, implicit knowledge. We do pattern drills, questions, learn some rules, do practice communication and this gradually becomes automatic behaviour - that's what most of us would think. And yet we also know that, in immersion situations, when we pay little attention to rules, we do seem to pick up language effectively. Is our assumption about structured practice and rule learning wrong? Is Krashen right?
Well, we don't know for sure and Krashen was soon criticised by fellow researchers in the 1980s partly because, they said, it is hard to clearly distinguish between what is conscious and what is unconscious. More recent brain research has led some applied linguists to propose a weaker version of Krashen's interface hypothesis. It's called, er, the weak interface position.
According to an interesting chapter from a book I read yesterday by Nick Ellis, research (including brain scanning) suggests that, whilst first language learning only occurs via implicit, unconscious means, the same does not hold true for second language learning. One obvious reason is that we already have implicit and explicit knowledge of a first language system which colours how we learn the second language. If you want to read the detail about this, have a look at the Ellis chapter. His conclusions from the research are:
1 Implicit and explicit learning are distinct processes.
2 Implicit and explicit memory are distinguished in their content, their
form, and their brain localizations.
3 There are different types of knowledge of and about language, stored in
different areas of the brain, and engendered by different types of educational
4 A large part of acquisition involves the implicit learning of language from
5 L1 transfer, learnt attention, and automatization all contribute to the
more limited achievements of exclusive implicit learning in SLA than in
6 Pedagogical responses to these shortcomings involve explicit instruction,
recruiting consciousness to overcome the implicit routines that are nonoptimal
7 Evaluation research in language education demonstrates that such FoF (focus on form) instruction can be effective.
I highlighted that last one. Ellis then goes to explore what the nature of the interface between explicit and implict knowledge might be. In particular, he examines the nature of consciousness, as it is viewed in psychological research. It's not very easy stuff!
For the language teacher, I suppose the key thing to emerge from this is that the Krashen view of the strong interface with regard to learning and acquisition may, stress may, be too simple. There is a growing consensus in the research literature that teaching and practising some explicit grammar is worth doing in classroom contexts. This would accord with the view of many practising teachers, but it is also fair to say that many teachers probably still pay too much attention to grammatical analysis rather than providing high quality, interesting target language input.