Earlier versions of the technology have already been tested successfully in people with paralysis, but the typing was slow and imprecise.
"Our results demonstrate that this interface may have great promise for use in people. It enables a typing rate sufficient for a meaningful conversation," said postdoctoral fellow Paul Nuyujukian at Stanford University.
The technology, developed researchers including Stanford scientist Krishna Shenoy, directly reads brain signals to drive a cursor moving over a keyboard and allowed monkeys to transcribe passages at a rate of up to 12 words per minute.
However, these have limitations, and can require a degree of muscle control that might be difficult for some people.
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For example, Stephen Hawking was not able to use eye-tracking software due to drooping eyelids and other people find eye-tracking technology tiring.
Directly reading brain signals could overcome some of these challenges and provide a way for people to communicate their thoughts and emotions, researchers said.
The technology involves a multi-electrode array implanted in the brain to directly read signals from a region that ordinarily directs hand and arm movements used to move a computer mouse.
They had tested individual components of the updated technology in prior monkey studies but had never demonstrated the combined improvements in typing speed and accuracy.
"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," Nuyujukian said.
Using these high-performing algorithms animals could type more than three times faster than with earlier approaches.
The monkeys testing the technology had been trained to type letters corresponding to what they see on a screen.
They might also be in more distracting environments and in some cases could have additional impairments that slow the ultimate communication rate.
Despite that, Nuyujukian said even a rate lower than the 12 words per minute achieved by monkeys would be a significant advance for people who are not otherwise able to communicate effectively or reliably.
The research was published in the journal Proceedings of the IEEE.