Whether we like to admit it or not, many of us have probably questioned if a bump in the night was actually a ghost at some point or another. And if you're really unlucky, you might even believe you've see a spirit in the flesh. But what exactly makes us feel like we are in the presence of something beyond the grave? Exploding head syndrome, sleep paralysis and even mould can be the source of a chill down your spine or the inkling that someone is watching. So, brace yourselves, as MailOnline explores five possible scientific explanations behind experiences of paranormal activity.

Have you ever laid wide-eyed in bed, convinced the rattle of a pipe or the creak of a floorboard was actually caused by something much more sinister? While it's easy to attribute these spooky sounds to the supernatural, researchers now believe sleep could be the cause of late-night ghostly sightings. In an article for the Conversation, Professor of Psychology at Goldsmiths University, Alice Gregory set about to determine how anxiety, REM sleep, and'exploding head syndrome' could offer a scientific explanation for late-night paranormal occurrences. It is during the REM (Rapid Eye Movement) stage of sleep when you are most likely to have vivid dreams. At this stage your body is also paralysed, perhaps as a safety mechanism to stop us acting out our dreams so that we don't end up attempting to fly (Stock Image) If you believe in the paranormal you might not be surprised if you hear stories of deceased loved ones appearing during the night, huge explosions heard just as someone is drifting off with no obvious cause, and other peculiar occurrences.

Accounts of mysterious flashing lights in the sky, spacecrafts and encounters with'real' aliens reflect high levels of public interest in UFOs and the belief that there is'something out there'. However, many psychologists are less convinced, and think they can provide more down-to-earth, scientific explanations. Belief in aliens has increased steadily since the birth of modern alien research in the 1940s and 1950s, following the news surrounding a classified US military project at Roswell Air Force Base, New Mexico. The theory that alien abductions are hoaxes may be true in a few cases, but there is no reason to assume that the majority of'experiencers' are frauds Surveys in Western cultures estimated belief in aliens to be as high as 50% in 2015. And despite the fact that it is considered rare, a significant number of people also believe they have experienced alien abduction.