Have you ever felt like you see something that does not exist in reality? Or did you ever hear a voice although there's no one around? Cases of visual or auditory hallucinations are more common than people think they are, according to scientists who are trying to give an explanation for this phenomenon.

How many people have hallucinations?

Hallucinations are a common thing for many people. Readers may be surprised to hear this, but researchers say that you don't have to be schizophrenic or drugged to have hallucinations. Did it happened to you to seem to hear a voice? Did you ever hear someone calling you, when in fact there is nobody around? This is a hallucination. How many times have did it happen to you to think that you have seen something, when in fact there was nothing there? This is also a hallucination.

John McGrath, a  professor from the Brain Research Institute in Queensland,  Australia said that many people who usually operate normally experience situations that might theoretically be called hallucinations.

How common are they?

Researchers have recently found that 1 in 20 people on the planet have gone through that -- they  saw or heard something that does not exist in reality while being awake. It is a false perception of reality and it can occur in different forms. The most common forms are visual or auditory hallucinations.

One of the major theories show that hallucinations occur when there is a "short-circuit" in the relationship between the frontal lobe of the brain and the sensory cortex, as Flavie Waters (an expert in neuropsychology  from the University of Western Australia) explained.

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Factors such as fatigue, stress, sadness, or trauma could be the cause of these short-circuits.

The research suggests that auditory hallucinations that occur in schizophrenia patients involves an overactive auditory cortex. This is the part of the brain that processes sound. Parkinson patients, in contrast, have a very active visual cortex, resulting in their brain images of beings or things that do not exist in reality.

However, the hallucinations are not always negative, intrusive, or frightening. More, they don't appear only if the person is sick. About 70% of healthy individuals are dealing with hallucinations just before falling asleep. For example, they think they hear someone calling their name, they think they hear the phone ringing, or they think they see someone next to their bed.