Autumn rain: being damp is inferred rather than truly felt. Photo: Getty
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On our nerves: what makes us itch or feel wet?

Michael Brooks’s science column. 

We’re all going to feel some unwanted damp on the skin over the next few weeks – welcome to autumn. But for those who feel wet due to a medical condition rather than the weather, researchers at Loughborough University have made what might just prove to be a welcome breakthrough.

It starts with a seemingly innocuous question: what makes wet stuff feel wet? By the end of this exploration, we will have encountered Joni Mitchell, patients with multiple sclerosis (MS) and a host of people suffering in ways that evoke Dante’s Inferno.

To some animal species, wetness is so critical to survival that evolution has equipped them to determine their state of external hydration: insects have humidity sensors. Human beings, however, don’t have wetness sensors on their skin, so understanding how we differentiate the sense of wetness from other sensations is a puzzle.

We have found clues in some of the tricks one can play on our species. The Loughborough researchers have shown that if you reduce the skin’s temperature using a dry cooling method, people feel as though their skin is wet. If you put something wet in contact with the skin, but at a temperature warmer than it, people don’t perceive it as wet.

So, clearly, we don’t feel wetness, we infer it. Our skin has an array of sensors for temperature and pressure, and it is a combination of these senses which tells us that something we are touching is wet. To find out what that combination might be, the Loughborough team experimented on 13 students, blocking and releasing their nerve sensitivities.

It turns out that crucial to wetness perception are nerves known as A-nerve fibres. Block the blood supply to these – using something like a blood-pressure cuff – and you become far worse at sensing wetness. Unsurprisingly, it is easier to sense cold wetness than warm wetness. The interplay of these different sensitivities enabled the researchers to create a model for the brain’s interpretation of wetness; in essence, it applies a weighting to each set of inputs in order to come to a probability-based conclusion on the body’s state.

This is more than an academic discovery because skin sensitivity is a serious medical issue. People suffering with MS frequently report an unpleasant feeling of cold wetness on their skin. It is a couple of short steps from feeling cold wetness to pain. One side effect of diabetes, for instance, can be dysaesthesia, when diabetics experience a burning or stabbing sensation on their skin, or feel the slightest touch from clothing or bedlinen as excruciating pain. In other cases, some diabetics can’t feel heat or touch sensitively enough to avoid injuring themselves.

It’s not just about the side effects of recognised diseases, though. There are various medical conditions associated with nerves sending pain signals in response to (apparently) nothing. Sufferers of central pain syndrome can report sensations such as being torn apart with hot knives, or being burned alive. No wonder it gets referred to as a Dante-type condition. Another oddity is Morgellons Disease. Joni Mitchell is perhaps the best-known sufferer of this unstoppable itching, which feels as if something is crawling under the skin. The medical orthodoxy is that the condition is indicative of a psychiatric disorder. However, if we knew more precisely what our skin’s nerve endings transmit to the brain, we might be able to help sufferers, delusional or not. 

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 08 October 2014 issue of the New Statesman, Grayson Perry guest edit

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Don’t shoot the messenger: are social media giants really “consciously failing” to tackle extremism?

MPs today accused social media companies of failing to combat terrorism, but just how accurate is this claim? 

Today’s home affairs committee report, which said that internet giants such as Twitter, Facebook, and YouTube are “consciously failing” to combat extremism, was criticised by terrorism experts almost immediately.

“Blaming Facebook, Google or Twitter for this phenomenon is quite simplistic, and I'd even say misleading,” Professor Peter Neumann, an expert on radicalisation from Kings College London, told the BBC.

“Social media companies are doing a lot more now than they used to - no doubt because of public pressure,” he went on. The report, however, labels the 14 million videos Google have removed in the last two years, and the 125,000 accounts Twitter has suspended in the last one, a “drop in the ocean”.

It didn’t take long for the sites involved to refute the claims, which follow a 12-month inquiry on radicalisation. A Facebook spokesperson said they deal “swiftly and robustly with reports of terrorism-related content”, whilst YouTube said they take their role in combating the spread of extremism “very seriously”. This time last week, Twitter announced that they’d suspended 235,000 accounts for promoting terrorism in the last six months, which is incidentally after the committee stopped counting in February.

When it comes to numbers, it’s difficult to determine what is and isn’t enough. There is no magical number of Terrorists On The Internet that experts can compare the number of deletions to. But it’s also important to judge the companies’ efforts within the realm of what is actually possible.

“The argument is that because Facebook and Twitter are very good at taking down copyright claims they should be better at tackling extremism,” says Jamie Bartlett, Director of the Centre for the Analysis of Social Media at Demos.

“But in those cases you are given a hashed file by the copyright holder and they say: ‘Find this file on your database and remove it please’. This is very different from extremism. You’re talking about complicated nuanced linguistic patterns each of which are usually unique, and are very hard for an algorithm to determine.”

Bartlett explains that a large team of people would have to work on building this algorithm by trawling through cases of extremist language, which, as Thangam Debonnaire learned this month, even humans can struggle to identify.  

“The problem is when you’re dealing with linguistic patterns even the best algorithms work at 70 per cent accuracy. You’d have so many false positives, and you’d end up needing to have another huge team of people that would be checking all of it. It’s such a much harder task than people think.”

Finding and deleting terrorist content is also only half of the battle. When it comes to videos and images, thousands of people could have downloaded them before they were deleted. During his research, Bartlett has also discovered that when one extremist account is deleted, another inevitably pops up in its place.

“Censorship is close to impossible,” he wrote in a Medium post in February. “I’ve been taking a look at how ISIL are using Twitter. I found one user name, @xcxcx162, who had no less than twenty-one versions of his name, all lined up and ready to use (@xcxcx1627; @xcxcx1628, @xcxcx1629, and so on).”

Beneath all this, there might be another, fundamental flaw in the report’s assumptions. Demos argue that there is no firm evidence that online material actually radicalises people, and that much of the material extremists view and share is often from mainstream news outlets.

But even if total censorship was possible, that doesn’t necessarily make it desirable. Bartlett argues that deleting extreme content would diminish our critical faculties, and that exposing people to it allows them to see for themselves that terrorists are “narcissistic, murderous, thuggish, irreligious brutes.” Complete censorship would also ruin social media for innocent people.

“All the big social media platforms operate on a very important principal, which is that they are not responsible for the content that is placed on their platforms,” he says. “It rests with the user because if they were legally responsible for everything that’s on their platform – and this is a legal ruling in the US – they would have to check every single thing before it was posted. Given that Facebook deals with billions of posts a day that would be the end of the entire social media infrastructure.

“That’s the kind of trade off we’d be talking about here. The benefits of those platforms are considerable and you’d be punishing a lot of innocent people.”

No one is denying that social media companies should do as much as they can to tackle terrorism. Bartlett thinks that platforms can do more to remove information under warrant or hand over data when the police require it, and making online policing 24/7 is an important development “because terrorists do not work 9 to 5”. At the end of the day, however, it’s important for the government to accept technological limitations.

“Censorship of the internet is only going to get harder and harder,” he says. “Our best hope is that people are critical and discerning and that is where I would like the effort to be.” 

Amelia Tait is a technology and digital culture writer at the New Statesman.