Research suggests why we hear voices when we are alone – 11/07/2023 – Science

A few years ago, scientists in Switzerland discovered a way to make people hallucinate. They did not use LSD or sensory deprivation chambers. Instead, they placed them in chairs and asked them to press a button that, a split second later, caused a rod to gently press into their backs.

A few rounds later, the volunteers had the strange feeling that there was someone behind them. Faced with a disconnect between actions and sensations, their minds came up with another explanation: a separate presence in the room.

In a new study published in the journal Psychological Medicine, researchers from the same lab used the “ghost finger” configuration to investigate another type of hallucination: hearing voices. They found that volunteers were more likely to report hearing a voice when there was a delay between pressing the button and touching the rod than when there was no delay.

The results suggest that the neurological roots of hallucinations lie in the way the brain processes contradictory signals from the environment, according to the researchers.

Hearing voices is more common than you might think, said Pavo Orepic, a postdoctoral researcher at the University of Geneva and author of the new paper. In research, scientists have found that many people without a psychiatric diagnosis — perhaps 5% to 10% of the general population — report hearing a disembodied voice at some point in their lives.

“There’s actually a continuum of these experiences,” Orepic said. “So, we all hallucinate — at certain times, like when we’re tired, we hallucinate more, for example — and some people are more prone to doing so.”

In the new study, as in previous work, Orepic and his collaborators had volunteers sit in a chair and press the button that made the rod touch their back. During some sessions, there was no delay between pressing the button and tapping the back, while in others there was a half-second delay, long enough to give volunteers the feeling that someone was nearby.

In all tests, volunteers listened to recordings of pink noise, a softer version of white noise. Some recordings contained recorded portions of his own voice, while others had fragments of someone else’s voice or no voice at all. In each test, volunteers were asked if they had heard someone speaking.

The study found that when people were already experiencing the sensation of a ghostly presence, they were more likely to say they had heard a voice when there was none. Furthermore, hearing a non-existent voice was more likely if, earlier in the experiment, they had heard bursts of noise with someone else’s voice in them.

This suggests that the brain was associating the hallucinated presence and the voice, Orepic said.

Interestingly, volunteers with no delay between pressing the button and feeling the touch on their back sometimes reported hearing a non-existent voice as well, and were more likely to do so if they had recently heard snippets of their own voice. If the volunteers unconsciously decided that they were responsible for the sensation of the finger on their back, they may have been primed to hear their own voice, the researchers said.

Taken together, the results support the idea that hallucinations may arise from difficulty recognizing one’s actions as well as being prepared to expect a specific outcome, Orepic said.

As time went on, people who experienced a ghostly presence in the test were increasingly likely to hear voices, which suggests that the brain was somehow drawing on past experiences to construct the impression of someone speaking.

Digging deeper into how the brain constructs the impression of a voice when there is none, Orepic said, may depend on help from healthy people who regularly hear voices — for example, mediums who feel they can communicate with the dead.

He cites ongoing studies at Yale with people who hear voices as a way to understand how these beliefs arise and how they can be controlled. For mediums, hearing voices is not necessarily unwanted. But perhaps, with their help, people whose hallucinations are distressing and disturbing can find some peace.