At this time of year, you will inevitably start to hear your fair share of supernatural stories.

We all have friends who claim to have glimpsed a ghost, have been pestered by a poltergeist or sensed a spiritual presence at some point in their lives.

But how seriously should we take them?

As Halloween festivities begin, we decided to speak to some psychology experts to help shed some light on one reason why people may think they’ve seen a ghost: sleep paralysis.

Two people watch a sleeping person
Are those people really in the room? (AP)

There seems to be a reasonably common trend in many of the reported ghost sightings, namely that they take place when people are in bed, often after waking at night.

One explanation for this is sleep paralysis, where someone is awake, but unable to move and with some elements of their dream encroaching on reality.

Although the area remains under-researched, Dr Alice Gregory, from Goldsmiths University, offered some insight into the phenomena.

She said: “Sleep can be distinguished into different stages. One distinction is between REM and NREM sleep.

“It is normal for the body to be paralysed during REM sleep – one explanation for this is that most dreaming takes place during REM sleep so if we are paralysed we can’t ‘act out’ our dreams.

“Sleep paralysis appears to occur when we wake up but retain certain features of REM sleep, specifically the paralysis.

“Hallucinations may occur during this experience – and those suffering from this experience may be unsure whether the hallucination was a dream or not. Features of REM sleep – this time the dream aspect – appears to be carrying over into wakefulness.”

Two men sleeping
Don’t believe everything you see the next time you wake in the night (Tim Ockenden/PA)

Chris French, also of Goldsmiths, reports having students who have had similar experiences, where they saw objects in their bedroom transform into menacing beings.

He said: “Around 40% of our psychology first-year students report having experienced sleep paralysis at least once.

“It can be frightening, but often made worse by a strong sense of presence and hallucinations.

“This could be the sensation of being touched or dragged, seeing people, creatures or moving lights or the sounds of voices or footsteps.”

People in Halloween costumes
Pinch yourself if these pop up in your bedroom.

These experiences have sometimes gone on to gain cultural significance as a result.

Professor French gives the example of Newfoundland, where a so-called Old Hag is talked of, whose sole purpose is, apparently, to suffocate the sleeper by sitting on them.

Outside of sleep paralysis, proving the paranormal is complicated for a number of other reasons.

Memory is recognised as a complicating factor when people feel they’ve encountered something spiritual, according to Professor French – as we tend to forget or change how an event occurred in our mind.

A lion
It’s not always Simba you’re sensing (Themba Hadebe/AP)

There is also some evidence which suggests the feeling that you are in a ghostly presence is prompted by electromagnetic interference with the lobes in your brain.

A scientific experiment using something called the God Helmet gave participants a mythical experience of a godly presence by sending magnetic fields through their head.

It could even be down to a survival instinct known as agent-detection – where we think there’s a presence nearby after evolution taught us to be wary of danger in strange situations, usually in case a lion jumps out.

Or, obviously, ghosts could exist – but we thought we’d provide some food for thought.