Fear is a universal human emotion, built on near-automatic responses that even our planet’s most basic life-forms can display. It has played an important evolutionary role, helping people anticipate and escape dangerous situations to stay alive. Feelings of fear provoke extreme reactions from what can be perceived as a threatening situation. But our relationship with fear is often misunderstood.

In 1649, the philosopher Descartes theorised that fear may be attributed to some childhood trauma. So if someone is scared by the mere sight of a cat, he wrote, the person may have been frightened by a cat as a child, an experience “imprinted in the brain”.

But childhood trauma is only one possible explanation for phobias, and it’s no longer the dominant one. One study in Behaviour Research and Therapy even suggested that children who experienced “significant injury” from childhood falls are less likely to develop a fear of heights later in life.

Researchers now trace phobias to a complex interplay of nature and nurture: Our genetics can predispose us to anxiety disorders, and the behaviour of people around us can condition us into fearfulness.

For example, parental behaviour before and during their children’s vaccinations was the biggest contributor to preschoolers’ “needle fear”, according to a 2016 study by researchers at York University.