ASMR (autonomous sensory meridian response) is that happily warm and tingling sensation that begins in the scalp and later excites other parts of your body. It owes its popularity to YouTube and the many odd YouTubers that have gotten millions of likes doing seemingly inane things such as flicking a lighter, clicking a stapler or dropping pebbles onto a container.

In ASMR, the sound's the thing. Unsurprisingly, some of the more watched YouTube videos are by beautiful girls, heavily made-up, seductively whispering and tapping the camera lens to elicit that elusive yet thrilling ASMR response. It's like you're in a bedroom with them.

One top ASMR YouTuber is said to have gotten more than 16 million views. That this silliness has survived online since the term ASMR was coined in 2010, testifies to the power of the mundane on our psyche in ways professionals still can't understand.

The grip of ASMR is still so strong. The New York Times reports YouTubers post more than 200 videos of ASMR triggers every day. Some of these ASMRers are so followed, they earn thousands of dollars and have millions of fans.

So, why is ASMR -- also called a "brain orgasm" -- driving so many people batty with delight?

One clinical description of ASMR describes this sensation as an experience characterized by a static-like or tingling sensation on the skin that typically begins on the scalp and moves down the back of the neck and upper spine. ASMR signifies the subjective experience of "low-grade euphoria" characterized by "a combination of positive feelings and a distinct static-like tingling sensation on the skin." It's most commonly triggered by specific auditory or visual stimuli, and less commonly by intentional attention control

ASMR is usually precipitated by stimuli referred to as "triggers," and most of the YouTube videos on ASMR are simply videos of these auditory and visual triggers.

ASMR is real, mind you. It's neither a sensory illusion nor is it hypnotism.

A study released in 2018 recorded participants’ physiological responses while watching ASMR videos. It revealed an obvious difference between those who self-identify as experiencing ASMR and those who didn't.

What's more, ASMR seems to have medical benefits, as well. The ASMR group had lower heart rates and increased skin conductance, which translates into a tiny increase in sweating.

The study also showed the ASMR experience is both calming (evidenced by the lower heart rate) and arousing (proven by the increased sweating). These indicators make ASMR a different experience from simple relaxation.

They also make ASMR distinct from the excitement of sexual arousal or the chills that occur when you hear something you really like.

ASMR has gained a cultish following in recent years, roping pleasure-seekers in with sounds of hair brushing and whispering. YouTube

Scientists have also examined how our brains function during ASMR. Researchers at Dartmouth College used functional MRI (fMRI) to see what happens in the brain when those who experience ASMR watched triggering videos.

They found ASMR activated the medial prefrontal cortex, an evolutionarily advanced part of the brain associated with self-awareness, social information processing and social behaviors.

Many of the ASMR stimuli that trigger these weird responses in us are truly unremarkable. These include listening to a softly spoken or whispering voice; listening to quiet, repetitive sounds; watching somebody execute a mundane task and listening to the tapping of fingernails onto a wooden or metal surface.

Scientists still aren’t sure if ASMR can be taught. A prevailing theory is ASMR is something one develops over a lifetime of experiences. This probably explains why certain types of peoples are more susceptible to ASMR than others.

But, studies have shown persons prone to ASMR are different from the rest. A study conducted in 2017 compared some 300 self-identified ASMR experiencers to an equal number who don’t experience the sensation.

It found ASMR participants got higher scores on Openness-to-Experience than their non-experiencer peers. ASMRers also had higher scores for neuroticism, which is a general trait describing those more likely to experience anxiety and negative emotions. ASMR participants also had lower levels of conscientiousness, extraversion and agreeableness, which seems to mean they’re more introverted.