Adam Haar Horowitz is the first to admit that whispering to strangers as they fall asleep “seems a little creepy.” He’d been mulling over the idea with fellow MIT master’s student Ishaan Grover a few years ago while thinking about ways to influence the dreamlike visions people see at sleep onset, a state known as hypnagogia. The pair wondered if quietly saying words or phrases to people in hypnagogia might influence the content of their thoughts and visions, thereby serving both as a tool to investigate human cognition and, ultimately, as a means to help people wield control over their dreaming brains.
Haar Horowitz didn’t end up whispering into strangers’ ears, but he, Grover, and other collaborators did find a way to execute the basic concept, using a more practical solution: a device that fits into a person’s hand to monitor changes in heart rate, muscle tone, and skin conductance—all of which help researchers determine the moment at which someone dozes off—paired with a computer or smartphone app that automatically plays audio prompts and records people’s spoken responses. The app “would speak to people when it guessed that they were at the end of hypnagogia before they go into something deeper,” Haar Horowitz says. After reporting what they were thinking about right at that moment, people would be allowed to nod off again, and the whole process could be repeated.