US scientists have invented brain-sensing technology which is able to interpret brain waves and convert them into the act of typing on a keyboard. Experts successfully demonstrated this by getting monkeys to transcribe actual passages from a Shakespearean play using only their minds.

Researchers from Stanford Bio-X – the namesake university's interdisciplinary biosciences institute – developed a multi-electrode array which is implanted in the brain. It directly reads signals from the brain region which controls hand and arm body movements, and the ability to manipulate a computer mouse.

The brain-machine interface also features computer algorithms which are able to translate the signals and interpret the letters that the brain wants to select when a cursor is hovering over a keyboard on the computer screen.

Monkeys trained to copy text from a screen

The researchers have been training monkeys to type letters and copy exactly what they see on a screen, and individual components of the system had been tested, but the system had not yet been tested altogether in order to evaluate its total typing speed and accuracy.

To prove that the technology works, the animals were set the task of transcribing passages from Hamlet and New York Times articles and – using the power of thought alone – a monkey was able to 'copy' the text on the screen, typing at a rate of up to 12 words per second.

In the video above, the monkey can be seen copying a famous quote, making a mistake, and then rectifying the mistake by deleting the incorrect characters, adding a space, and continuing with the sentence.

The researchers think the technology will enable people who have movement disabilities to type much faster than existing solutions, which focus on tracking eye movements – or in the case of renowned physicist Stephen Hawking – tracking the movements of individual muscles in his face.

The drawback of using these solutions is that eye-tracking technology can tire the eyes very quickly, and some people can find the degree of muscle control required in order for the computer to pick up the required typing command challenging to cope with.

"The interface we tested is exactly what a human would use. What we had never quantified before was the typing rate that could be achieved," said Paul Nuyujukian, a neurosurgery postdoctoral fellow at Stanford specialising in brain-machine interfaces.

"Our results demonstrate that this interface may have great promise for use in people. It enables a typing rate sufficient for a meaningful conversation."

Brain-machine interface would be much less tiring than other aids

While the results are promising, the researchers warn that people will be unlikely to type at speeds as high as the monkeys, as they first need to think about what they want to communicate, and also figure out how to spell specific words. However, this would still be a huge improvement on how people with movement disabilities are able to communicate at the moment.

The research also showed that the sensor implanted into the monkeys' brains remains stable for several years. Although the implants were inserted four years before the experiment began, the animals have not experienced any side effects, and the sensor performs as consistently as it did when it was first implanted.

The researchers are now collaborating with a team of scientists from the Brain-Machine Interface initiative of the Stanford Neurosciences Institute, to run a clinical trial that will test the implant in people.

The paper, entitled A Nonhuman Primate Brain–Computer Typing Interface, is published in the journal Proceedings of the IEEE.