The Science of Ghost-Busting

By Cat Thomson, Class of 2020.

Image courtesy of Lennart Wittstock via Pexels

It’s now October which means that Halloween and the spooky season is just around the corner. If you’re like me, you’re planning out your costume and are getting ready to share some ghost stories with friends.

We all (hopefully) know that there is no evidence to support the existence of ghosts.  Scientists have systematically shown that it simply is impossible for ghosts to exist. According to a survey conducted by the Pew Research Centre, almost one in five people believe that they have seen or been in the presence of a ghost. If we know scientifically that ghosts don’t exist, why do people still claim to have interacted with them?

Don’t be fooled by your senses!

It turns out that we can’t always trust our senses; they have a knack for tricking us. Have you ever thought you heard someone calling your name, only to turn around and realise that there’s no one there? Maybe you’ve seen the outline of a person in the dark, but once you’ve taken a second look you realise you’re all alone. When this happens, your brain is actually hallucinating.

We trust our senses completely as we go about our day to day life; and rightfully so! We need them to understand the world around us. Therefore, when our senses betray us and send us information that isn’t actually real, we are naturally inclined to believe it. I mean, we believe everything our senses tell us!

Your brain is the culprit

Your brain is a master at combining all of your incoming sensory information in order to understand what’s going on in the world around you. The brain can do this in one of two ways. Firstly, it can process information in a “bottom-up” manner. In this instance, your brain is sent a jumbled-up mixture of information from your senses. It’s the brain’s job to sort through all of this and find meaning in what’s going on. The brain is really good at this but can sometimes work too hard and find meaning in sensory information that is actually meaningless. This is what happens when we think we’ve seen a ghost, but there’s actually nothing there. Scientists call this phenomenon pareidolia.

Our brain is naturally hard-wired to see faces, even from minimal stimuli. This could explain why our brain is often tricked into seeing human-like ghosts. Test yourself below. The video contains examples of everyday objects. Does your brain interpret them as faces?

The Second way your brain can interpret information is what’s known as “top-down” processing. In this case, your brain filters out the important information that your senses are giving you and then fills in the rest. This is what happens when someone claims that they can hear ghosts. If someone is scared and on edge, they often believe that a ghost could be talking to them. So, when they hear a random sound, their brain will assume that the noise was a ghost!

Why do some people see ghosts when others don’t?

 In 2018, a team of psychologists conducted a study that investigated peoples’ experiences with sensing things that aren’t really there. Participants were asked to look at 60 images of fuzzy black and white “noise”. In some of these images, a face would briefly appear. Other images contained no faces at all. For each of the images, the participants had to state whether they saw a face or not. The researchers found that participants who reported seeing faces when there actually weren’t any present also claimed to have experienced more hallucination-type experiences (like seeing ghosts) in their everyday life.

Black and white “noise” image courtesy of _DJ_ via flickr

Maybe seeing ghosts depends upon your brain’s predisposition to experiencing hallucination-type events. If you’re like me and are a bit of a ghost sceptic, you might have a harder time trying to see one, as your brain is less likely to be tricked by your senses. However, if you are ready to get spooky this Halloween and have someone tell you a ghost story, be sure to use your critical thinking! Your senses might betray you, but just remember, it’s all in your head!