What makes people afraid of the dark?

Loss of vision. Sight is our strongest sense and some of our natural predators, such as the big cats, had better night vision than our ancestors did. Our ancestors also had to watch out for enemy raids; even today, we may justifiably fear being burgled.

But our greatest fears come from our own minds. Many children, and some adults, are terrified of the monster under the bed. This is called the ‘sense of presence’ and is often associated with sleep paralysis, when you wake up unable to move. These monsters are due to unusual activity in areas of the brain. Then there are all those ideas that we don’t like to face – our shame, guilt, anger, anxiety or whatever it may be. These seems far worse in the dark because our brains are deprived of the visual input that keeps them busy and suppresses those unwanted thoughts.