We’re only a week away from 31 October – celebrated as Halloween in many countries.

Halloween, or All Hallows Eve, is thought to date back over 2000 years to the Celtic festival of Samhain, which means ‘Summers End’ in Gaelic. It was like their New Year, with the year divided into its lighter and darker halves (essentially summer and winter). Of course, in the northern hemisphere the end of October coincides with the end of their lighter time of year, so they would have finished their harvest and be preparing for the dark winter ahead. Celts believed it was a time when the boundary between our world and the Otherworld was thinner, so spirits could pass into our world.

In Australia, Halloween isn’t celebrated as much as it is in many other countries, but we do embrace plenty of other scary things throughout the year, like watching scary movies and TV shows, and of course we have plenty of deadly animals that lots people are scared of (like sharks and highly venomous snakes). But why do we even experience fear?

It’s basically a survival mechanism. Early in our evolutionary history, before we were top of the food chain, our brains would prevent us from becoming the dinner of other animals by activating what we now call the ‘fight or flight’ response. When the amygdala (a section of our brain) perceives a threat, it triggers the hypothalamus (another section of our brain) to stimulate the production of specific chemicals and hormones, such as adrenaline, so that our heart races faster, our blood pressure goes up, we start to sweat, our veins constrict to keep blood in our major muscles, our non-essential systems like the digestive system turn off, and we become extra alert – all so that we can either run away from the threat as fast as possible, or fight the threat to save ourselves.

The amygdala also connects to the hippocampus, the part of our brain that stores our memories, so that the next time we encounter the same threat it reminds us of the fear we felt the first time, and can make us afraid again.

Some of us let out a high pitched scream when we are scared. While this conveys our fear, it’s a sound that our amygdala perceives as a danger signal, so it puts everyone around us on high alert too!

We are born with only two instinctive fears – the fear of falling (which stops us from falling off cliffs, or for some of us these days, from jumping off a high diving board), and the fear of loud sounds. The rest are learned, either from social cues and culture (e.g. our parents repeatedly telling us the lion is scary) or through our past experiences (e.g. we have been bitten by the lion in the past).

So why do we deliberately put ourselves in situations that scare us, like watching scary movies, or going on scary rides? There are a few reasons. One of the hormones released during the fight or flight response is dopamine, which makes us feel happy, so we actually get a natural high through experiencing fear. Additionally, after the initial fear is over, our brains release more chemicals and hormones that relax us again, and produce a feeling of relief, which is a great sensation. And of course, when we’re watching scary films, we are usually in a space that we know is completely safe – so we experience the genuine fear, but then our conscious brain immediately catches up and realises we’re safe, so the fear is put aside, but we still feel the rush. This combination is responsible for some of you being daredevils.