When you tune into Twitch streamer Perrikaryal’s channel, you might see her playing FromSoftware’s role-playing game epic Elden Ring with fourteen, unfamiliar black sensors stuck to her scalp. It’s her—as she said during an informational stream earlier today—“just for fun” electroencephalogram (EEG) device, something researchers use to record the brain’s electrical activity, which she’s repurposed to let her play Elden Ring hands-free.

“Okay what and how,” publisher Bandai Namco responded to a clip of Perri (whose name seems to refer to the perikaryon, the cell body of a neuron) describing how she linked brain activity to key binds to help her play the game, shared by esports reporter Jake Lucky on Twitter.

Cue the disbelief (“I’ve gotten a lot of stuff online being like, […] ‘are you for real?’” Perri says in that Twitter clip) and cries of Ex Machina.

It does look incredible—in the clip, you see Perri simply say “attack” to her screen like a gamer girl Matilda and then, after a short delay, her Elden Ring character responds by casting Rock Sling at an irritated boss. But I spent my undergrad fixing eye-tracking devices to my friends’ heads while they helped me fill my lab requirements, and I know that, although brain technology can look complicated, some of it was still easy enough for me as a 19-year-old. So I reached out to my former classmate, University of Michigan cognitive neuroscience PhD candidate Cody Cao, for his thoughts.

“EEG has really good temporal resolution,” he said, “meaning that the collected neural response to gaming stimuli is down to milliseconds. If the neural responses corresponding to available actions present vastly different neural patterns, algorithms can decode or differentiate which is which after training. Then, you play the game with EEG.”

But playing a game with your brain—something Elon Musk tried to shock the public with in 2021, when his brain-computer interface company Neuralink released a video of a monkey playing Pong using its technology—won’t give you an advantage.

“Decoding is still janky,” Cao told me, “60 percent to 70 percent accuracy is considered pretty good,” compared to 90 to 100 percent accuracy in performing an action manually (which also requires your brain!).

“It takes algorithms a lot of training to get to an acceptable performance. They likely need to experience a lot of different examples of the same thing (like Perri saying ‘attack’ before attacking) to be able to account for a vast majority of attacks,” Cao continued. “It’s like FaceID on your iPhone—it gets better with the more examples it sees.”

Perri also emphasized in her stream today that she isn’t necessarily innovating, but bringing the possibilities of EEG usage to the general public’s attention.

“It’s not that crazy, it’s really easy to do. And it’s been done since 1988,” she said about gaming with her brain. “It’s not necessarily anything new that I’m doing, I’m just not sure that it’s very well known.” But now you know, and maybe you’ll figure out how to mind control me a grilled cheese that doesn’t hurt my stomach next.