In the 1940s, a group of Russian researchers sealed five prison inmates in an airtight chamber.

The prisoners were dosed with an experimental gas that would prevent them from sleeping. Their conversations were electronically monitored, and their behaviour was observed through secret two-way mirrors.

For the first few days, everything seemed fine. But after the fifth day, they slowly began to exhibit signs of stress. They became paranoid and stopped talking to one another, whispering about each other into the microphones.

Nine days in, the screaming began. Two of the sleepless prisoners just started running around the chamber, yelling so hard their vocal chords nearly broke.

Suddenly, however, the voices stopped, and the chamber became dead quiet. Fearing the worst, the researchers announced that they were opening the chamber. But a voice from inside answered: "We no longer want to be freed."

On the 15th day, the stimulant gas was replaced by fresh air. The results were chaotic.

One inmate was dead. The inmates had been severely mutilated, flesh torn off their bodies and stuffed into the floor drain. They seemed to have ripped open their own abdomens, and even eaten their own flesh.

They refused to leave by force, fighting back with a powerful aggression none of the researchers could have imagined they possessed. They fought furiously against being removed and anesthetised; one even tore his own muscles and ripped his bones apart during the struggle. When asked why they had mutilated themselves, each gave the exact same answer: "I must remain awake."

The researchers wanted to kill the prisoners and remove all traces of the experiment, but their commanding officer demanded it be resumed immediately, with the researchers joining the inmates in the sealed chamber. Horrified, the chief researcher shot him point blank.

He then shot and killed the two last surviving subjects, and set about covering up all that had taken place.

WHAT THE HELL DID I JUST READ?

Okay, first thing's first: that story didn't actually take place in real life.

The creepy picture of the chamber above? An artistic illustration digitally altered by a random internet browser. Sorry.

Entitled 'The Russian Sleep Experiment', it's an internet legend of which the oldest version can be traced back to a Creepypasta Wiki page on August 10, 2010. The user who posted it is named 'Orange Soda', but the author's real name is unknown.

To this day, internet users continue to debate the veracity of this infamous story, despite the fact that it originated on an online forum thread devoted to seeing who can drill up the best "urban legend".

You've read stories like this. There was Slender Man, the story of a lanky faceless giant who frequents children's playgrounds. He gained the most attention when he inspired two young girls in Wisconsin to attempt to brutally kill their friend (unfortunately, that part was true). Then there's Jeff The Killer, the chalk-faced teenager-turned-murderer who goes insane and becomes a bloodthirsty psychopath.

The thing is, when you first read these horrific stories, they almost seem just realistic enough to work. After all, scientists have been studying the effects of sleep deprivation throughout the 20th century.

Even today, there are wide reports of meth-induced hallucinations resulting from a lack of sleep. Why wouldn't a story of a crazy Russian experiment from the 1940s seem plausible?

After careful analysis, Sara McGuire of Venngage has shared a visual report detailing exactly what it takes for a horror story to go viral.

HOW TO CREATE A VIRAL HORROR STORY

McGuire read and analysed samples of 72 top 'Creepypastas' across the internet.

She then identified the seven most common ingredients used in the top stories. In order from most to least common, they are:

UNEXPLAINED PHENOMENON (71 per cent)

The report found that humans are most thrilled by the unknown; things that we will never understand. The story needs to involve a strange occurrence or creature whose origins are unknown, but has a lasting impact on our psyche.

FIRST-PERSON NARRATIVES (68 per cent)

The report argues that if a story is told as a personal account, there's always the possibility that it might be true, even if you know it realistically couldn't be. The Russian Sleep Experiment was actually the only story of the top 10 that wasn't told in the first-person voice.

MONSTERS AND SUPERNATURAL BEINGS (61 per cent)

The success of the Russian Sleep Experiment is attributed to the fact that the "monsters" actually come from a very real, human place, which seems to make them more plausible. This also explains the popularity of the Slender Man.

CLIFFHANGERS (53 per cent)

This is common in horror movies, or even just book chapters and TV shows. You leave the reader or viewer with a chill and keep the mystery alive. The report notes this is especially effective in cases where the reader is left to question whether something similar could happen to them.

MURDER (46 per cent)

It goes without saying that most people are afraid of murder, which is why it's a plot device in almost half of these stories.

CREEPY IMAGES (24 per cent)

Fun fact: Slender Man originally started as a Photoshop contest. Users on a forum were asked to digitally alter an ordinary photo to create a creepy internet legend. And it can be really hard to shake a disturbing image.

CREEPY VIDEOS (6 per cent)

The rarest of the ingredients, only two Creepypasta stories originally used a video, according to McGuire. She notes that most of the time, videos are created by fans of a viral story after it's already become famous.

McGuire's report found that stories which used four of these ingredients - no more, no less - gave a story the best chance at going viral. The Russian Sleep Experiment is the most viral 'Creepypasta' story on the internet, with a total of 64,030 shares. It used four ingredients: an unexplained phenomenon, murder, monsters (in this case, humans-turned-zombies) and a series of creepy images of poor black and white quality to suggest they authentically match the time period.

So that's that. If you want to go viral, McGuire says there are some basic rules to comply with:

• Tell a personal anecdote where possible. It will make you seem more relatable to the reader and it can be used in virtually every writing context to add colour to a story.

• Get your Photoshop on. Obscure, creepy images that aren't quite bad (or polished!) enough to be false tend to work very well. Slender Man is a perfect example.

• Leave readers wanting more. Cliffhangers are deliberately frustrating. You want a satisfying ending or conclusion, and instead, you're left filled with questions. Readers are more likely to share these types of stories because they're more debatable.

Alternatively, just shut down your device now and walk away. These stories alone are creepy enough to keep us up for two weeks straight - no experimental gas required.