An online community has blossomed around a phenomenon called Autonomous Sensory Meridian Response that gives a subset of people a euphoric feeling in their brains that science has yet to explain.

I am sitting in bed with my feet curled under me on a dark fall evening before the first snow. My hair is tucked beneath noise-canceling headphones that are playing the sound of a woman gently blowing into my ears. She is whispering, intimately exhaling breath on one side before moving to the other, back and forth. A shiver starts at the crown of my head and tiptoes like an electric shock down the knobs of my spine. I have to take the headphones off. The feeling, while pleasant, is simply too much.

I am having an Autonomous Sensory Meridian Response (ASMR), a strange, tingly sensation, known in some corners of the Internet as a brain orgasm. Whispering is a primary trigger, but anything from the sound a pen makes when drawing on a piece of paper to rhythmic, monotonous speech can spark an episode. And it’s not just about sounds. Having someone focus specifically on you–such as when an optometrist performs an eye exam or when your hairdresser cuts your bangs–can also invoke the same feeling; the sensation of someone gently tracing lines on your back or stroking your hair can incite that familiar fizzle.

People experience ASMR in different ways, which makes describing it especially difficult. For me, whispering, one-on-one attention or someone lightly grazing my hair, neck or back provokes a physical reaction that is almost violent in its quest for pleasure. For others, the feeling is less distinct: some may be simply lulled into a comfortable state of relaxation without experiencing any physical reaction at all.

Hundreds of people create ASMR videos and upload them to YouTube for the purpose of helping people relax. The community, which originated on YouTube with one popular video of a woman whispering, has grown tremendously since its inception in 2009, and now boasts almost 2 million videos. The Reddit forum dedicated to ASMR has over 55,000 subscribers and the Facebook page has almost 11,000 likes. A simple search for “ASMR” on YouTube yields thousands of thumbnails of primarily young, attractive women dragging makeup brushes across their hands or pursing their lips and blowing into the camera.

[youtube http://www.youtube.com/watch?v=TgpaytdDIaA]

The term ASMR was coined by Jenn Allen, a 30-year-old New Yorker who works in Healthcare IT. She started the ASMR Research Institute, an unofficial organization that relies on volunteers to help analyze the neuroscience and psychology behind why the phenomenon exists.

Karissa Ann Burgess, who’s currently studying in a clinical psychology PhD program, is in charge of experimental research and data for the organization, but said that the group has yet to begin significant work in finding answers. Still, they’ve floated some theories: “Dopamine could be involved, serotonin–the feel-good hormones,” Burgess told TIME by phone. “There’s also some interesting theories that it might be a sort of bonding phenomenon and triggers the release of oxytocin, which is the bonding hormone.”

Scientists haven’t yet provided many answers about ASMR and the phenomenon hasn’t really been subject to any sort of rigorous study, meaning that the how and why surrounding it go largely unanswered.

Steven Novella, a prominent neuroscientist and assistant professor at the Yale University School of Medicine, wrote briefly on the topic of ASMRs on his blog, The Ness. He believes that, despite the dearth of medical research, ASMRs are most likely real, and the neurological causes behind them could range from mini seizures to hardwired evolutionary reactions.

“Perhaps ASMR is a type of seizure. Seizures can sometime be pleasurable, and can be triggered by these sorts of things,” Novella writes on his blog. “Or, ASMR could just be a way of activating the pleasure response. Vertebrate brains are fundamentally hardwired for pleasure and pain – for positive and negative behavioral feedback.”

The videos posted online intended to activate that pleasure response are strange and sometimes borderline creepy, enough so that when I first found out about them I did not really want to be one of those people who reacts to them, whose spine fizzles in response to a stranger pretending to give me a makeover or brush my hair. But it is, like the name suggests, autonomous–something that happens without my control.

[youtube http://www.youtube.com/watch?v=sfo0ZSgc86A%5D

The acts required to trigger an ASMR are admittedly intimate. The sensation is compared to an orgasm because it can feel similar, just centered at the top of the body instead of the bottom, so you’d be forgiven for confusing ASMRs for something sexual. But perhaps that’s another reason they are so difficult to decipher, especially if you don’t experience them yourself: ASMRs are intimate but not sexual, feel-good but not orgasmic, private but not secret.

“The less intense state that a lot of people get into is sort of a buzzing in the head. It literally feels like their brain is being pushed down, so it’s getting heavy and at the same time buzzing is happening in the back of your head,” said Maria, who runs a popular YouTube account called Gentle Whispering where she posts videos of herself performing a series of ASMR triggers, such as whispering and role playing characters like doctors and teachers meant to guide watchers into the euphoric state of ASMR.

The active community that has formed around the phenomenon largely consists of video creators who themselves experience ASMR and want to help contribute content to the canon to help other people reach the same relaxed state.

“Yes, ASMR is this relaxing feeling, but it’s way more than that,” said Ilse, a young Dutch woman whose website, The Water Whispers, and YouTube channel generate some of the most popular ASMR content on the web. “The community is such a loving and humble community because it’s about taking something by watching video and, because you’re grateful, you give something back. That’s why I think the community is one of the most unique ones in the entire world that you’re going to find.”

Because the videos tend to be recorded by young attractive women, and because YouTube is not a particularly welcoming place for women in general, the comments beneath the videos are their own sort of story, with all the drama and tension and hurtfulness inherent to any online community.

And it’s not just creepy comments that can pile up under the videos–many of which, for better or worse, also attract white knights to defend the honor of the YouTuber in question. One of ASMR’s most popular and prolific users, who went by the screenname CuteBunny992, was driven off the platform last year after a hacker gained access to her account and tried to paint her as a slut and pedophile by deleting all of her uploads and publishing inappropriate videos. Though she was widely loved within the ASMR community, she hasn’t been back since.

But the growth in ASMR seekers hasn’t been stopped by events like that.

“For me it’s just a very calming state of mind, and sometimes it feels like the top of my head is tingling,” said Amber Gordon, an employee at Tumblr in New York City who watches ASMR videos every night before falling asleep. “In a way, it’s kind of addictive.”