Devices Like Neuralink Can Decode Your Thoughts

Brain-computer interfaces give people with disabilities the ability to communicate by decoding signals in the brain. But what happens when these people don't want to communicate? A new study finds that a person's inner speech can be decoded in much the same way as attempted speech, raising questions about how intrusive BCIs can be. The idea that technology can decode a person's inner voice is "unsettling," Duke University professor Nita Farahany, who explores the advance of neurotech in her 2023 book The Battle for Your Brain, tells NPR. "The more we push this research forward, the more transparent our brains become."

Because BCIs rely on tiny electrodes to translate neural signals into speak, paralyzed patients traditionally have to try hard to produce a word or sentence they want to speak but physically can't, which can be tiring. Looking to help them, Stanford University researchers wondered if BCIs could also translate the more subtle brain signals involved in imagined speech, when a person is simply thinking about a word or sentence. It worked. With help from artificial intelligence, researchers working with four existing BCI users "were able to get up to a 74% accuracy decoding sentences from a 125,000-word vocabulary," says Erin Kunz of Stanford University's Neural Prosthetics Translational Laboratory, lead author of the study published Thursday in Cell.

This eased communication for the study participants, but raised serious questions about privacy, as the interface could potentially read the patient's mind at any time. Researchers settled on applying password protection so the BCI could only analyze imagined speech when it observed a specific phrase, in much that same way that Apple's AI assistant activates in response to "Hey Siri." But this suggests "the boundary between public and private thought may be blurrier than we assume," Farahany tells NPR. She notes that while surgically implanted BCIs will be regulated by the FDA, other versions marketed to everyday consumers, including gamers, may not face the same scrutiny.