When we think of hearing voices, we often associate it with psychiatric disorders like schizophrenia. However, recent research suggests that hallucinations can be induced in most individuals under specific circumstances. Scientists from Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL) and France’s University Savoie Mont Blanc sought to investigate the triggers of auditory-verbal hallucinations (AVH) and the underlying mechanisms behind them. Through their study, they discovered that these hallucinations occur due to a combination of factors, including deficits in self-monitoring and the influence of pre-existing beliefs.
The researchers devised an innovative method to induce AVH in a controlled laboratory environment. By integrating voice perception techniques with sensorimotor stimulation, they aimed to explore the contributions of both prominent theories related to AVH. The experiment involved 48 participants who were asked to poke a button in front of them, triggering a robotic arm to poke them from behind. Throughout the experiment, the participants wore headphones that played a mix of ‘pink noise,’ similar to a waterfall, and snippets of voices, both their own and others’.
As expected, participants reported feeling a presence behind them due to the poking sensation. However, some individuals also reported hearing voices through the headphones, even though no voices were actually present. Interestingly, the likelihood of experiencing auditory hallucinations increased when participants heard other people’s voices before their own and when there was a delay between button pushing and arm poking. It appeared that participants were unconsciously inventing a voice to accompany the sensation of someone standing behind them.
These findings provide support for both self-monitoring deficits and hyper-precise priors as potential triggers for hallucinations. The inability to accurately distinguish one’s own self from the surrounding environment, along with the strong influence of pre-existing beliefs, played an important role in experiencing AVH. Notably, the frequency of hallucinated voices rose as the study progressed, suggesting that the duration of the experiment influenced the occurrence of phantom sounds.
Gaining insight into how hallucinations can be triggered is crucial for understanding their significance in conditions such as Parkinson’s disease. By unraveling the complexities of AVH, researchers can enhance their understanding of the brain’s mechanisms and potentially develop more effective treatments for these conditions. Although hearing a voice in one’s head may be disconcerting, this study offers reassurance that it may not warrant immediate alarm. However, anyone experiencing such symptoms should consult a medical professional for further evaluation and guidance.
The groundbreaking research conducted by the EPFL and University Savoie Mont Blanc sheds new light on the link between hallucinations and deficits in self-monitoring. The findings indicate that auditory-verbal hallucinations can occur in most individuals given the right conditions. This study serves a dual purpose, providing novel insights into AVH phenomenology and supporting opposing accounts about its triggers. By expanding our knowledge in this field, we are one step closer to better understanding and treating neurological conditions that involve hallucinations.
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