Do you spend your Halloween wandering through haunted attractions and watching scary movies? Or would you rather indulge in some of the sugary treats on offer? Though vastly different, these activities are all central to the spooky season. In this post, we explore the science behind some of Halloween’s most beloved traditions.
Trick – the biology of being afraid
Halloween began as a Celtic festival to mark the end of summer and the harvest. The Celts believed that on this night, the boundary between the living and the dead was at its thinnest, allowing spirits to roam freely.
However, it was John Carpenter’s 1978 film Halloween that transformed this holiday into a night of terror. Since then, horror has become a much-loved movie genre. But why do we enjoy fear in the first place?
Why fear feels fun
Fear is the body’s natural response to a perceived threat. Exposure to frightening sights or sounds activates the amygdala, the part of the brain responsible for processing fear. This triggers the body’s fight-or-flight response, releasing adrenaline which heightens heart rate and sharpens focus.
This surge of energy is designed to protect us, but in a safe setting—like watching a horror film—it becomes thrilling.
Adrenaline rushes are often followed by an elevated mood or sense of relief. This means that horror movies can feel like an emotional roller coaster: fear leads to excitement, and anxiety turns into joy.
According to researchers from Johns Hopkins university, we often feel the strongest positive emotions immediately after experiencing something negative. Think of the relief of finding your lost keys or delivering a flawless presentation you’ve been worried about for days!
This contrast in emotions is why so many people seek the safe scares of horror.
Still, not everyone enjoys being scared. For many, the thought of wandering through a haunted house is enough to send a chill down their spine. Whether we enjoy horror often comes down to our “protective frame.” This protective frame allows us to experience fear in a safe and controlled way. There are three components:
Safety: Knowing we are safe as the danger is at a distance.
Detachment: Remembering that what we are seeing isn’t real.
Control and confidence: Feeling we can manage the situation in front of us.
The more of these components we have, the more likely we are to enjoy a good scare.
Treat — the chemistry of candy
Of course, not everyone craves a fright. For many, Halloween is all about sweet treats. This tradition comes from “guising,” when Scottish and Irish children would spend Halloween performing poems or jokes in costume in exchange for food. After World War II, American suburbs popularised trick-or-treating as we know it today: centred around sharing sugary snacks.
Sugar rush
Sugar doesn’t just make food taste good—it also (to a certain extent!) makes us feel good.
Sugar stimulates the brain’s reward system, a network that links different areas of the brain together. When it is activated, dopamine is released, making us feel short bursts of happiness and satisfaction. This reward system serves the evolutionary role of making eating enjoyable, reinforcing behaviours that are essential for survival.
The catch, however, is that this dopamine rush wires us to crave more and more sugar. That’s why one sweet can so easily turn into an entire bag. It’s a bit like reading a good (text)book: the first chapter is sweet, the next one even better, and before you know it, you’ve read the whole book in one sitting.
Sour power
Sitting at the opposite end of the sugary spectrum, sour candies are among the most popular of sweets. Their tangy flavour comes from products like citric acid (lemon and lime), malic acid (apple), and tartaric acid (grape). These acids release hydrogen ions that activate taste receptors on the tongue, producing that distinctive pucker effect.
The intensity of the sourness depends on the pH: the lower the pH, the more hydrogen ions are present, and the sharper the sensation. To balance tang and enjoyment, sugar is added to give a comforting sweetness after the initial kick. This combination further triggers the brain’s reward system, giving us that familiar dopamine-fuelled sugar rush.
So, whether you prefer the adrenaline rush of a horror film or the dopamine hit of a sweet treat, Halloween is the perfect time to indulge. It’s a holiday that appeals to all sides of our brains—the thrill-seeker who loves a good scare, and the sweet-tooth who delights in candy-fuelled fun.
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