To protect users’ privacy, they chose a passphrase to activate the device that was unlikely to come up in everyday speech: “Chitty Chitty Bang Bang,” the title of the 1964 Ian Fleming novel and 1968 movie. The technology would start translating thoughts when it detected the phrase, which, for one participant, it did with 98.75 percent accuracy.

In the tests, the researchers asked the participants—all four of whom have some trouble speaking—to either attempt saying a set of seven words or to merely think them. They found the patterns of neural activity and regions of the brain used in both scenarios were similar, but the inner thoughts produced weaker signals.

Then, the team trained the computer system on the signals produced when participants thought words from a 125,000-word vocabulary. When the users then thought sentences with these words, the device translated the resulting brain activity. The technology produced words with an error rate of 26 to 54 percent, making it the most accurate attempt to decode inner speech to date, Science reports.