For the first time, researchers have found a way to non-invasively translate a person’s thoughts into text. Using fMRI scans and an AI-based decoder trained on a precursor to ChatGPT, the system can reconstruct brain activity to interpret the gist of a story someone is listening to, watching or even just imagining telling. Ian Sample speaks to one of the team behind the breakthrough, the neuroscientist Dr Alex Huth, to find out how it works, where they hope to use it, and whether our mental privacy could soon be at risk