Monkey see: macaques’ brains strongly encode visual stimuli that are outside the animals’ awareness. Credit: Pete Oxford/Nature Picture Library

The reaction to neuroscientist Doris Tsao’s latest preprint, she says, has been “surreal”. Tsao, at the University of California, Berkeley, described the study on social media on 17 October. Ten days later, her summary has drawn more than two million views and 11,000 likes.

Posted on bioRxiv, the study 1 probed the brains of macaques ( Macaca mulatta ) during a visual-perception experiment. Using only the monkeys’ neural activity, Tsao’s team managed to reconstruct with high fidelity not only images that the animals were consciously seeing, but also images that were in front of their eyes but escaped their awareness.

Three reasons why AI is not conscious and perhaps never will be

Previous studies in monkeys have detected neural activity in response to content they are not aware of, but only as weak signals.…