The human brain is undoubtedly a complex and enigmatic organ that continues to baffle scientists and researchers. We might automatically associate hearing voices with neurological conditions like schizophrenia. However, recent studies have revealed that most brains can be tricked into hearing voices that aren’t really there, given the right conditions.
Researchers from the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and the University Savoie Mont Blanc in France embarked on an intriguing investigation. Their primary goal was to understand how auditory-verbal hallucinations (AVH) might be triggered in the mind. This phenomenon occurs when an individual hears a voice, but there is no speaker present.
Previously, studies have proposed two primary hypotheses to explain the occurrence of these hallucinations. The first theory suggests that they are caused by an inability to correctly distinguish oneself from the surrounding environment. The second theory proposes that strongly held beliefs or prior assumptions overpower an individual’s perception of reality. To investigate these hypotheses, the research team introduced a unique method.
In their published paper, the researchers described the development of a new method to induce AVH in a controlled laboratory environment. They combined techniques from voice perception with sensorimotor stimulation to explore the contributions of both major AVH theories. Building upon a previous experiment, the researchers equipped participants with headphones that played a mix of “pink noise” (a waterfall-like sound) and intermittent snippets of voices, including both their own and other people’s.
During the experiment, the participants engaged in a push-button test, in which they poked a button in front of them. Simultaneously, a robotic arm poked them in the back. The team manipulated the delay between the button push and the arm poke. As expected, the participants reported feeling a presence behind them due to the poking sensation. However, intriguingly, some participants also reported hearing voices that weren’t actually present through the headphones.
The researchers observed that the phenomenon of hearing voices was more common if the participants heard someone else’s voice before their own. Additionally, when there was a longer delay between the button push and the arm poke, the participants were more likely to hear phantom sounds. It appeared as though those involved in the experiment were fabricating a voice to align with the sensation of someone standing behind them.
These findings lend credence to both prevailing theories of hallucination triggers. The participants demonstrated a failure to accurately self-monitor their surroundings, as well as an inclination to be influenced by strong beliefs about their environment. Interestingly, the frequency of hallucinated voices increased as the duration of the tests lengthened, with participants more likely to experience the phantom sounds towards the end of the experimental session.
Understanding how hallucinations can be triggered has crucial implications for comprehending their association with conditions like Parkinson’s disease. Moreover, it serves as a reminder that if you do hear a voice in your head, it may not necessarily warrant immediate alarm. However, it is always prudent to seek medical advice if you have concerns.
This groundbreaking study sheds new light on the mysterious phenomenon of auditory-verbal hallucinations. By investigating the triggers and mechanisms behind hearing voices, researchers have provided experimental support for the coexistence of deficits in self-monitoring and the influence of hyper-precise priors. The intricate workings of the human brain continue to captivate and astound us, reminding us of the complex nature of our own minds.
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