They say you never really know somebody until you live under the same roof. But in the five years I’d known my 20-something former coworker, Craig, I thought I knew what to expect. When he asked to rent out the spare loft in my apartment two summers ago, I knew he wasn’t going to win any awards from Good Housekeeping. At work, his desk had been a graveyard of yellowed newspapers, cups of stale, half-drunk coffee, and crumpled energy-bar wrappers. Okay, he’s a little bohemian, I thought. But nothing I can’t handle. So, he moved in.

A few days later, I returned home from work to find the apartment completely dark, the window shades drawn tight. When I climbed the stairs and peered around the doorway, there was Craig, seated in the glow of his laptop. “Hey, didn’t hear you come in,” he said, yanking off an oversized pair of headphones and blinking to refocus his eyes. “Whatcha watching?” I asked tentatively. Thus began my official introduction to the mesmerizing world of ASMR.

I’d already heard a little about ASMR, or autonomous sensory meridian response, before this moment, but not much beyond the basics. A physical and emotional experience that 20 to 40 percent of people claim to have, ASMR is often described as a shiver or tingle that travels up the spine or lingers at the top of the head, triggered by particular sounds and images. The web is filled with hypnotic ASMR videos of whispering, finger tapping, scratching sounds, gentle…