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Many people experience Autonomous sensory meridian response (ASMR), a relaxing sensation often triggered by gentle whispering which creates a "low-grade euphoria" characterized by "a combination of positive feelings and a distinct static-like tingling sensation on the skin. We are finally working out what it is and that it can be good for you.

The phenomenon first came to people's attention in 2007, in an online forum thread titled "weird sensation feels good". Many names were suggested, notably "attention-induced head orgasm" -- a misnomer because the feeling is not as sudden or short-lived as an orgasm, and is distinct from sexual arousal.

The term that stuck was coined in 2010 by cybersecurity expert Jennifer Allen: "autonomous sensory meridian response", or ASMR. She wanted something that represented the key elements of the sensation, but that sounded scientific, so people wouldn't be embarrassed to talk about it. It worked: those who experience the phenomenon are now a thriving online community. For instance, the ASMR subreddit has about 165,000 subscribers. The sensation has been popularised by pharmacologist Craig Richard of Shenandoah University in Virginia, who set up the website ASMR University.

"A lot of people said 'woah, I thought I was the only one who experienced this'"

Science then began to catch up. The first studies of ASMR began to appear in 2014, with work by Emma Barratt and Nick Davis, both then at Swansea University, UK. Barratt was a master's student interested in synaesthesia: the phenomenon in which people's senses merge, so they hear colour or see sound.

"A friend approached me to ask if ASMR was related to synaesthesia," says Barratt. "That was the first time I'd heard of it."

To start investigating, she and Davis asked people in online ASMR communities to fill out a questionnaire. From the 475 responses, they learned that episodes were pretty consistent: typically described as "a tingling sensation which originated towards the back of the scalp and progressed down the line of the spine and, in some cases, out towards the shoulders".

Four triggers were most popular, each favoured by more than half of respondents: whispering, personal attention, slow movements and "crisp sounds" like tapping fingernails.

Barratt and Davis had established the basic reality of ASMR. Nevertheless, many questions remained unanswered -- like what proportion of people experience it.

The only estimate of prevalence comes from Giulia Poerio at the University of Sheffield, UK, who surveyed guests at a public neuroscience event in 2014. Of 91 people, 53 had experienced ASMR, 15 hadn't and 23 weren't sure. It is clearly no niche sensation, and it seems far more common than synaesthesia, which is only experienced by 4.4 per cent of us.

The responses also illustrated how misunderstood the phenomenon is. "A lot of people who said they had ASMR either thought everyone had, or they thought 'whoa, I thought I was the only person who experienced it'," says Poerio.

There is also some information about who does and doesn't experience it, thanks to two studies from 2017. Stephen Smith at the University of Winnipeg, Canada, and his colleagues asked 290 people with ASMR and 290 matched people without it to complete a test that measured the five main personality traits. People with ASMR had higher scores on openness-to-experience and neuroticism, and lower levels of conscientiousness, extroversion and agreeableness. The second study partly backed this up: people with ASMR scored high for openness-to-experience and low for conscientiousness.

However, it isn't clear what that means, says Daniel Bor at the University of Cambridge. "It's quite possible that there is some underlying genetics that makes people both susceptible to ASMR and neurotic," or the high openness-to-experience could simply reflect the people who try odd-sounding videos.

It doesn't help that nobody actually knows what ASMR is yet, although there are many ideas. Certainly, it resembles several known neurological states. Barratt and Davis looked for a link with synaesthesia, but found no significant difference in the frequency of synaesthesia among people who did and didn't experience ASMR.

They also compared it to "flow": the mental state in which you concentrate fully on a task and it starts to feel almost automatic. Their survey revealed that people who experienced flow more readily also had more ASMR triggers. But anyone who has experienced ASMR knows it isn't flow: it is fuzzy, almost trance-like.

A more promising comparison is "frisson". This sensation is similar to shivering, complete with goosebumps, but is triggered by an emotional experience like powerful music. It is sometimes called "musical chills". People often reportedly confuse ASMR and frisson -- but ASMR lacks the shivery, electric element. A 2016 review argued that ASMR is relaxing while frisson is arousing. Perhaps they are two ends of a spectrum.

Whatever ASMR is, it has real effects. In a study published in June, Poerio and her colleagues monitored people's heart rate and skin conductance -- a measure of emotional arousal -- while they watched ASMR videos. Everyone's heart rates slowed, but the hearts of those who experience ASMR slowed more.

The team also found that those with ASMR had increased skin conductance, indicating greater emotional arousal. "We expected to find a reduction," says Poerio. "It might be to do with the fact ASMR is a complex emotional experience."

To really understand the phenomenon, however, we need to know what is going on in the brain during ASMR. In 2013, a student named Bryson Lochte at Dartmouth College in New Hampshire scanned the brains of people experiencing ASMR as part of his thesis. But the study went unpublished for years while Lochte studied medicine.

"The brain, at rest, is functioning differently in those with ASMR," says co-author Jennifer Kornelsen at the University of Manitoba, Canada. She says this may help explain the sensation: the altered connectivity may reflect "a reduced ability or tendency to inhibit sensory-emotional experiences".

However, Bor is unconvinced. He says the participants weren't matched by personality. "All the effects could be due to personality differences," he says. "It might not have anything to do with the ASMR trait."

Kornelsen says the team has since scanned the brains of people while they are experiencing ASMR, but the results aren't yet published. However, in June, Lochte's study finally appeared, with Richard as a co-author.

Lochte and his colleagues used functional MRI to monitor brain activity in 10 ASMR-sensitive people as they watched videos that trigger the sensation. The scans showed significant activation in parts of the brain associated with reward and emotional arousal. Similar patterns are seen in frisson, suggesting the two sensations are indeed related.

It is still unclear what all these findings mean, other than that the brain of someone who experiences ASMR seems to work differently. But why?

It could be that this phenomenon evolved for an evolutionary purpose, says Davis, not least because it is so often triggered by personal attention. "If you look at great apes being groomed, I suspect they're feeling something like ASMR," he says. "They're receiving close personal attention from another ape. I think it's a rewarding state to be in."

Richard suggested something similar in 2014: that ASMR triggers neurological pathways involved in emotional bonding. In line with this, Lochte's study found that the brain activation sparked by ASMR was similar to that seen in people and animals experiencing friendly behaviour. Poerio's volunteers also reported greater feelings of social connection after ASMR. Maybe it is an intense version of the feeling we all get when loved ones tend to us -- and videos can be a shortcut to it.

Genuine Benefits

But others have doubts, arguing that the brain sometimes just does odd things. "Why should some visual stimulus cause head tingling?" asks Bor. "I can't see any evolutionary purpose for that whatsoever."

Regardless of any explanation, the benefits seem genuine. Barratt "really didn't expect ASMR to be therapeutically applicable", but she and Davis found otherwise in 2014. "People showed this amazing elevation in mood during ASMR, but also that mood elevation persists for a few hours after," says Davis. "It makes you happier when you're doing it and it keeps you happy."

What's more, those who were generally less happy showed a greater change. "People who are quite down are using ASMR to improve their mood," says Davis. "People with chronic pain were using it, I don't want to say to treat, but at least to distract from the pain." For those who can, ASMR may be a simple way to relieve pain and stabilise mood.

Poerio's June study backs this up. A lower heart rate implies people are less stressed and more relaxed. When it comes to pain relief, it could be that the sensation of ASMR overpowers or distracts from the pain temporarily, or relaxation and improved mood might help with the pain. "It shows there's a physiological benefit," she says. Heart rates fell by 3.1 beats per minute during ASMR, which was similar to the effects of music-induced relaxation for people with cardiovascular disease. It is early days, but "our research would support this idea that potentially it could be used for therapeutic benefit", she says.