Right now, in order for Gallant to read your thoughts, you have to slide into a functional magnetic resonance imaging (fMRI) machine – a huge, expensive device that measures where the blood is flowing in the brain. While fMRI is one of the best ways to measure the activity of the brain, it’s not perfect, nor is it portable. Subjects in an fMRI machine can’t move, and the devices are expensive and huge.

And while comparing the brain image and the movie image side by side makes their connection apparent, the image that Gallant’s algorithm can build from brain signals isn’t quite like peering into a window. The resolution on fMRI scans simply isn’t high enough to create something that generates a clear picture. “Until somebody comes up with a method for measuring brain activity better than we can today there won’t be many portable brain-decoding devices that will be built for a general use,” he says.

Dream reader

While Gallant isn’t working on trying to build any more decoding machines, others are. One team in Japan is currently trying to make a dream reader, using the same fMRI technique. But unlike in the movie experiment, where researchers know what the person is seeing and can confirm that image in the brain readouts, dreams are far trickier.

To try and train the system, researchers put subjects in an fMRI machine and let them slip into that weird state between wakefulness and dreaming. They then woke up the subject and ask what they had seen. Using that information, they could correlate the reported dream images – everything from ice picks to keys to statues – to train the algorithm.