In 1947, a covert Soviet test facility carried out experiments into sleep. The researchers took several test subjects – prison inmates – and sealed them in an airtight space that was then filled with an experimental stimulant gas designed to prevent sleep. Over the next few weeks, the researchers planned to observe their hapless test subjects by way of hidden microphones and two-way mirrors.

At first things ran smoothly, but after a week the test subjects began to exhibit signs of stress. They became withdrawn and paranoid, whispering into the microphones about their fellow inmates. But then, a few days later, the screaming started. The prisoners suddenly turned frantic, they ranted and raved, and screamed themselves horse. Some apparently screamed so hard they practically ruptured their vocal cords. And then it all went silent.

The experience was terrifying, so the experimenters tried to stop the study and open the chamber. However, they were stopped from doing so when a voice, one of the prisoners, announced “We no longer wish to be freed”.

By the time the researchers cut the gas and opened the chamber a few days later, most of the inmates were dead, apparently having mutilated themselves or one another. Some had reportedly resorted to cannibalism. Those who remained alive were in a state of psychosis, refusing to leave and refusing to sleep again. Of course, the Soviet authorities tried to remove all evidence of this grisly event from the record.

If you are familiar with this story, or some version of it, then congratulations, you have come across an urban legend that has made its way onto the internet in recent years. The Russian Sleep Experiment, as it is known, was originally a creepypasta story – a kind of short horror story designed to sound plausible – that has now mutated into a living urban legend. Much like the popular Slender Man that lurked and crept its way from a work of internet fiction to very real tragic events, the Russian Sleep Experiment now has a life beyond the authors who originally created it.

But what makes stories like this so “believable”? Or, to put it another way, why do some stories become urban legends when others do not, and why do we accept them?

A new folklore 

Urban legends are effectively a form of modern folklore. The stories can vary in their content, from the mundane culinary experience – the Kentucky fried mouse story – and creature sightings – alligators in the sewers – to the supernatural encounters like Slender Man and the Vanishing Hitchhiker. All these stories are united by a sense of strangeness, albeit to varying degrees, as well as a sliver of believability.

This is an important factor for a budding urban legend. No matter how ridiculous, or worrying the content, it has to have a small amount of credibility to survive. This is usually achieved by combining elements of the familiar with the unfamiliar, but only in measured doses.

Previous research into the popularity of folk stories, such as those in the Grimm Brother’s fairy tales, has shown that the more popular narratives are those that only use a few supernatural components. For instance, Little Red Riding Hood and Cinderella are fantastical stories with a few references to the weird, but they are also recognizable and extremely popular. In contrast, The Donkey Lettuce (sometimes Cabbage), which appears in the same collection of stories is filled with supernatural elements and yet is barely known.

It seems our minds have a credibility threshold beyond which our critical thinking starts to object. The same may be true for urban legends. If they include too many surprising details, then the story becomes less enjoyable or believable.

The psychology of urban legends

In terms of psychology, this could be explained in relation to thinking styles and what is known as the dual processing model. According to this idea, we have two ways of processing information that are distinct but nevertheless interrelated.

Essentially this is a kind of “system one” and “system two” approach, Dr Neil Dagnall, a cognitive and parapsychological researcher at Manchester Metropolitan University, told IFLScience. The former favors emotional, instinctive, and subjective evaluations and the latter focuses on objective and critical thinking. 

[P]eople are likely to engage with urban legends because they're interesting anecdotes or something topical. So [people] latch on to it from that subjective side, and then are less interested in validating its accuracy and more interested in the story for the story's sake.

Dr Neil Dagnall

Although these processes work in parallel, each style draws on different cognitive resources. Critical thinking, which relies on established rules of logical reasoning, is more mentally taxing. It’s intentional and attentional, whereas emotional thinking is less demanding, relying on general cognitive processes to interpret information, and is mostly automatic.

Previous research into dual processing theories has found that belief in paranormal phenomena is closely related to “system one” thinking, that is, intuitive rather than critical thinking. So perhaps something like that is happening with the belief in urban legends.

“[P]eople are likely to engage with urban legends because they're interesting,” Dr Dagnall explained. “They're nice little stories, or they're interesting anecdotes, or something that's topical. So [people] latch on to it from that subjective side, and then are less interested in validating its accuracy and more interested in the story for the story's sake.”

This explanation contrasts with others that try to view humans as simply being prone to believing outlandish ideas, that they are generally non-discerning. Or, as psychologist Gordon Pennycook argues, humans will generally believe “bullshit”.

Essentially, this suggests some people are simply not discerning and will rely on system one thinking. They are not particularly selective with the information they believe and instead endorse things that are not true. As such, they will believe any form of bullshit, from urban legends to paranormal events to ridiculous conspiracy theories.

But Dagnall believes there is more going on here. We know, for instance, that even within the conspiracy theory world, believers in one claim may not necessarily believe in another. For instance, he explains, “I might think Elvis faked his death, I might think Elvis was murdered, but I don't necessarily think that's true of Marilyn Monroe.” Equally, someone who believes in the Flat Earth conspiracies may not necessarily believe in aliens or be opposed to vaccinations.

Although it is true that people who believe in conspiracies often do have other unusual beliefs, the situation is more complicated and contextual than simply saying they just believe “bullshit”.

Even “within people who engage with urban legends,” Dagnall says, “they're going to be more critical of some of those urban legends than other ones, and the degree to which they're susceptible to them will be influenced by other factors, such as how plausible they think they are.”

At the same time, because of the rise of the internet and social media, how such stories spread has changed. Not only is it easier for people to circulate various new urban legends across the internet, but many of us are also too busy to apply critical thinking to everything we see.

“There’s less opportunity to evaluate stories or to deal with them...," Dagnall notes. "[I]n the past, if you just get it in an email and you may get a precautionary thing, it's more likely to be the focus of your attention. Now, you just get them popping up all over the place.”

This returns us to credibility. Good urban legends are stories that have something believable about them. So the alligators in the sewers story, for instance, works well because it has historical precedence in places where they are native. It is therefore plausible that alligators or crocodiles may have infiltrated other sewer systems, even in places like New York City.

This too is true for the Russian Sleep Experiment story. The Soviet Union is remembered as a cruel and barbaric regime that demonstrated a staggering disregard for human life, especially under Joseph Stalin. Couple this with contemporary stories about unethical human experiments, such as those performed by the Nazis in the Second World War, or the CIA's Project MKUltra and you have the framework for a believable narrative about abused inmates and sinister experiments.

So like any worthy urban legend, the story may not be true, but for some it may nevertheless feel like it could be.