“They record from the motor areas of the brain, the areas that control the mouth, larynx, tongue, etc,” Huth said. “What they can decode is: how is the person trying to move their mouth to say something?
“Our system works at a very different level. Our system really works at the level of ideas, of semantics, of meaning.”
That’s why the text generated by the decoder doesn’t exactly reproduce the words a participant imagines or hears.
“It’s the gist. It’s like the same idea, but expressed in different words.”
The study generated excitement in the research world, said cognitive scientist at the Queensland University of Technology Professor Greig de Zubicaray, but there are elements of the approach that limit the method’s practical applications.
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“In English, in particular, you have a very predictable subject, verb, object word order, or SVO,” de Zubicaray said. “They’ve acknowledged that their decoder struggled with figuring out who was actually performing an action or who was the subject of the sentences.”
The decoder was also better at interpreting thoughts about concrete objects as opposed to abstract ideas.
“Recovering meaning about something more abstract, such as truth, happiness or love, would be far more difficult for this particular approach.”
The researchers noted the technology could become more useful – and contribute to devices that allow people who can’t talk or use sign language to communicate – if it can be applied using cheaper, more portable scanning techniques such as EEG or MEG scans.
The researchers proved their technique could only decode thoughts with the participant’s full cooperation and depended on gathering 16 hours of data first, so the technology couldn’t be used to tune in to private thoughts.
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“Of course, this could all change as tech gets better, so we believe it’s important to keep researching the privacy implications of brain decoding and enact policies that protect each person’s mental privacy,” Tang said.
Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.