An "emotionally aware" computer system designed to read people's minds by analysing expressions will be featured at a major London exhibition.

Visitors to the Royal Society Summer Science Exhibition are being invited to help "train" the computer how to read joy, anger and other expressions.

Its designers say there are potential commercial uses, such as picking the right time to sell someone something.

But it may also help improve driver safety and help people with autism.

The computer, which is connected to a camera, locates and tracks 24 facial "feature points" such as the edge of the nose, the eyebrows and the corners of the mouth.

A total of 20 key facial movements - including a nod or shake of the head, a raise of the eyebrow or a pull on the corner of the mouth - have been identified.

Combinations of these movements, which are thought to represent underlying emotions, are then fed into software and used to detect the same facial combinations in real-life situations.

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