Hallucinations can occur in both healthy and unwell people. There are a number of things that can trigger visual hallucinations in people with no psychiatric illness. Drugs, sleep deprivation, high fever, loss of vision, loss of hearing and migraines. Even a flickering light can induce hallucinations. Visual hallucinations arise when external stimuli are overwhelmed by internally generated spontaneous patterns of neural activity.

You might have had them yourself. If you’ve ever heard a text alert only to find there was no message, or felt a phantom vibration in your pocket when you heard your cell phone ring from the table across the room, you’ve had a kind of hallucination. 

These sorts of experiences exist on a continuum, from the feeling that the phone has rung when you’re expecting an important call all the way to full-blown visual and auditory hallucinations.

A hallucination is a sensory perception and a delusion is a false belief.

Hallucinations are defined as experiences and sensations that are not perceivable to others. To the person experiencing them, however, they may seem real, urgent, and vivid.

People have reported seeing animals, innate objects and people that are not present. They may report seeing ghosts or angels. Others detail complicated scenes or bizarre situations.

Our brains doing their best to make sense of a chaotic and ambiguous world and one in twenty normal people will experience hallucinations at least once in their lifetime. Our visual system works like a camera: the eyes record an image and the brain processes it. But this does not consider conceptualization – what is not optically seen – the brain’s overreliance on previous information.

Hallucinations should never be confused with illusions and delusions:

  • An illusion is a real reaction – to a real sensation – with a misattributed cause.
  • A delusion is a real reaction to a real sensation, but which is given an unreal, impossible, bizarre or overly significant cause.

Hallucinations can be a normal part of the human experience,

as long as they don’t take over a person’s life.