Over the land freckled with snow half-thawed
The speculating rooks at their nests cawed
And saw from elm-tops, delicate as flower of grass,
What we below could not see, Winter pass.

Edward Thomas

Cambridge has finally thawed. When the wind blows now it does not bring ice and perishing cold. It might blow you off your bicycle, but you will be warm enough.

And so the birds are nesting. In the garden at OISE Cambridge we have nesting pair of long-tailed tits. The nest is neat and small, with a suitably tiny aperture, and an elongated for to accommodate the birds’ absurd tails.

The tits are on to something. Leaving aside for a moment whether the tail can be said to be efficient or not, an efficient form will ultimately follow function in some way. With language, for instance, the brain will not let you learn what is not relevant to you. The language you have at your command will, in the end, accurately map the use you have for it. You will not spend resources which your brain does not think necessary.

This partly explains the plateau – the tendency of language learners to stop learning at a given level of competence, suitable to their needs. It also explains why some learners can make sudden dramatic progress, if their needs change. If all your meetings and telephone calls are, overnight, in English, with native speakers, you will sweat profusely for a few months, and then settle at a new, much higher, but still adaptive, level.

Creating that need in the classroom is part of the expertise of teachers – forcing students not to be content with what they can currently accomplish. But it is a tricky business. Humans are easily scared. They resist. Their brains are out of their conscious control. Half the time they’re looking out of the window, thinking about something completely different (which is of course another well-worn survival technique), such as why a long-tailed tit wants such a long tail in the first place.