Why are children used in horror films?

Children are very unpredictable. They have a vivid imagination that can be magnificent or terrifying.

Children are universally perceived as innocent beings who can't cause harm. It is for that reason that directors and producers use them in horror films.

Children are found in most families. It's far more terrible to imagine that someone who is so innocent can be next to you and cause horror.

Children are what most people see as raw material for learning and observing. It is a lot easier to make a child do something terrible than convince an adult with it.

The use of children in horror elements isn't new. It makes a great plot twist when the cause of horror is the child in a movie.

Children are pure, so when they are evil, it is the idea of pure evil that is terrifying. (See Why Do Some People Like Horror Movies?)

It's difficult for most people to hate children. So, when you realize that a child is the cause of terror, you can't help but have mixed feelings that disable you from thinking clearly.

Most people would rather help the possessed or lost child than step away from them. That always gives a movie some sort of longevity. (See A list of Survival Horror Movies)

Children are unpredictable. So, it's the fear of the unknown that's haunting after discovering that a child is the cause of horror.