Watch what you say. Scientists in England have developed a computer that can not only read lips, but can tell the difference between languages.

Mouth movements can differ according to the language spoken.

Researchers at the University of East Anglia's School of Computing Sciences developed the technology by statistically modeling the lip motions of 23 bilingual and trilingual speakers. The resulting system is able to identify the language spoken by an individual with "very high accuracy," according to the university. Identifiable languages included English, French, German, Arabic, Mandarin, Cantonese, Italian, Polish, and Russian.

What gives you away? The movement of your articulators--when you wag your tongue, jaw, and lips, you are generating the measurable characteristics of visual speech, the recognition of which is known as lip reading. Computer vision has already been used in lip reading, or "feature extraction," but this is the first time computers have been "taught" to recognize different languages, according to UEA, http://www.ee.surrey.ac.uk/Projects/LILiR/update/jn/UpgradeReport.pdf (PDF).

"This is an exciting advance in automatic lip-reading technology and the first scientific confirmation of something we already intuitively suspected--that when people speak different languages, they use different mouth shapes in different sequences," said Professor Stephen Cox, who led the research along with Jake Newman. "For example, we found frequent 'lip rounding' among French speakers, and more prominent tongue movements among Arabic speakers."

The discovery could have practical uses for the deaf, law enforcement, and military units serving overseas, the researchers predict. With a little fine tuning it may also help you figure out what language your teenager speaks.