
The 'multivariate pattern recognition' technique uses a computer trained to recognise certain changes in brain activity associated with actions. It can predict intended actions before they occur with 70 percent accuracy.
"In future it will be possible to read even abstract thoughts and intentions out of patients' brains," said the scanner's inventor Professor Dr John-Dylan Haynes.
"One day even the intention to 'open the blue folder' or 'reply to the email' could be picked up by brain scanners and turned into the appropriate action."
The technique was tested on volunteers who were told that they would be shown two numbers which they could choose to add or subtract. A few seconds later the numbers would appear and they would perform the calculation.
The experiments also confirmed a long standing theory of brain function, that intentions are formed in the centre of the brain and then migrate to the surface when translated into actions.
Professor Haynes has called for an ethical debate to be held before the system is used on humans for law enforcement or even to predict criminal intent.