Surprising impact of presence hallucinations on social perception

Using virtual humans for hallucination detection in Parkinson's disease via numerosity estimation.

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Neuroscientists at EPFL have discovered a means to modify our perception of other people and monitor specific kinds of hallucinations. Both healthy individuals and those who have Parkinson’s disease can experience this. Physicians can utilize this online exam to screen for hallucinations.

There is a cautious side to both humans and animals. If there aren’t any tigers in the jungle, it’s better to pretend that there are than to fail to spot a hungry tiger.

Neuroscientists at EPFL have discovered that individuals who suffer from hallucinations, particularly those brought on by diseases like Parkinson’s disease, frequently believe there are more people in a room than there are. However, when asked to estimate the number of boxes in a room, which are not social objects, they don’t overestimate. This suggests that the overcounting is related to social perception. 

The head of EPFL’s Laboratory of Cognitive Neuroscience, Olaf Blanke, said, “It’s unexpected that people with Parkinson’s disease, who are recognized for having problems with movement, also have trouble with social perception. This implies that hallucinations may exacerbate the way Parkinson’s disease affects our perception of social cues.”

Researchers in neuroscience have examined presence hallucinations, a subtype of hallucination in which the subject experiences an unseen presence nearby. Even though they are mild in comparison to other hallucinations, Parkinson’s patients frequently experience them early on—sometimes even before diagnosis. They may also be a sign of Parkinson’s disease-related cognitive deterioration.

The study found that these presence hallucinations lead people to overestimate the number of people around them. This suggests that the brain processes responsible for these hallucinations also affect how we count people. The brain adds the invisible presence into the count, but only when counting people.

Researchers in neuroscience have examined presence hallucinations, a subtype of hallucination in which the subject experiences an unseen presence nearby. Even though they are mild in comparison to other hallucinations, Parkinson’s patients frequently experience them early on—sometimes even before diagnosis. They may also be a sign of Parkinson’s disease-related cognitive deterioration.

Researchers tested the concept that presence hallucinations lead people to overestimate the number of persons around them using “technopolis,” a combination of virtual reality and robotics. In this investigation, technodelics were employed to create hallucinations brought on by technology. 

Virtual reality presented fleeting shots of people in a room, moving too quickly to tally. The user had artificial presence hallucinations as a result of robotics poking their back out of sync with their movements. The investigators discovered that healthy people using technology did overcount.

Lead author Louis Albert explains, “Our technodelics setup offers an objective way to measure hallucinations, which are usually subjective. We engineer and induce hallucinations, providing a clear measure of susceptibility at a given time.”

To monitor hallucinations at home, researchers developed a simplified version of the numerosity experiment that can be done online. This test provides an objective way to measure hallucination susceptibility in patients without the need for specialized staff or equipment.

Patients can complete the exam at home using a computer or tablet, making it reasonably priced and available to a wide range of people. Those experiencing presence hallucinations tended to overcount more than those without in research involving 170 Parkinson’s patients. This shows that the test may help identify people at risk of cognitive loss so they can receive therapy early.

This study found that presence hallucinations unexpectedly affect our perception and comprehension of social contexts. It demonstrates the importance of considering social elements in hallucination research. Technodelics, a novel approach, allows us to understand more about hallucinations in many medical contexts. This may result in more effective strategies for handling them.

Journal reference:

  1. Albert, L., Potheegadoo, J., Herbelin, B. et al. Numerosity estimation of virtual humans as a digital-robotic marker for hallucinations in Parkinson’s disease. Nature Communications. DOI: 10.1038/s41467-024-45912-w.
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