YOU are in a foreign country, looking for an art gallery, so you stop a passer-by in the street to ask for directions. Instead of talking loudly and slowly in your own language in the vain hope of making yourself understood, or attempting to communicate using an improvised form of sign language, you simply speak into your handheld computer, which instantly translates what you are saying. Then it translates the person's response for you.

That is the vision of computer translation researchers, who have been struggling to develop a real-time, easy-to-use system capable of accurately turning speech into other languages and back again. The technology has so far fallen far short of expectations.

However, in the next couple of years we can expect an explosion in translation technologies, including camera cellphones that can capture text on road signs, say, and translate them into another language, and real-time automatic dubbing to ...