Even healthy people can be tricked under the right conditions into hearing voices that aren’t really there.
This is reported by Science Alert with reference to research by Swiss and French scientists.
Usually, hearing voices that are not there is associated with neurological diseases, such as schizophrenia.
Scientists from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Université Savoie Mont Blanc in France wanted to investigate how auditory-verbal hallucinations (AVH) can be induced in consciousness. Because that is where people hear a voice when there is no speaker.
Participants in the experiment heard a static hiss of pink noise,
they pressed the button and felt a stab in the back
Previous research suggests that these hallucinations are caused either by an inability to correctly distinguish oneself from the environment, or by strongly held beliefs that override what is actually happening in the environment.
The team wanted to test both hypotheses.
After hearing a static hiss of pink noise, the participants pressed a button, and after a while felt a robotic arm poke them in the back.
In the next test, the tick delay was varied and the volunteers wore headphones that played a mixture of waterfall-like “pink noise” and occasional snippets of their own and other people’s voices.
As in the previous button-press test, participants reported feeling a presence behind them due to the poking. Some of them also reported hearing voices that were not in the headphones.
Hearing voices was more common if people heard someone else’s voice before their own, and if there was a delay between pressing the button and poking the hand.
It looked as if the test subjects were inventing a voice based on the sense that someone was standing behind them.
These results, according to the researchers, are enough to suggest that both theories of hallucinations are correct: the participants did not know how to properly control their environment and were influenced by strong beliefs about what was happening around them.
Importantly, the frequency of hallucinating voices increased with the duration of the tests, so participants heard phantom sounds more often at the end of the experiment.
Ultimately, knowing how these hallucinations can be caused is important to understanding how they are related to diseases such as Parkinson’s disease.
It also suggests that if you do hear a voice in your head, it may not be an immediate cause for alarm. Although, if you are concerned about it, it is better to consult a doctor.
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