You stub your toe on the bedpost. Before your brain even registers the pain, a word explodes from your mouth – sharp, loud and oddly satisfying.

Far from being a simple slip in manners, swearing is a reflex rooted deep in the structure of the human body, drawing on networks in the brain and autonomic nervous system that evolved to help us survive pain and shock.

Research shows that a well-placed expletive can dull pain, regulate the heart and help the body recover from stress. The occasional outburst, it seems, isn’t a moral failure – it’s a protective reflex wired into us.

The impulse to swear begins far below the level of conscious speech. Most everyday language originates in the cerebral cortex, where ideas are shaped into words. Swearing, however, lights up a much older network – the limbic system, which governs emotion, memory and survival responses.

Important parts of the limbic system include the amygdala, which acts like an emotional alarm system, and the basal ganglia, a group of connected structures that help control movement and automatic behaviour, including instinctive vocalisation.

These areas send quick signals down........

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