Australian researchers have found a new way to induce and measure hallucinations in people.
The University of NSW scientists say the results of their work suggests these complex experiences share a common mechanism with normal visual perception.
You don’t have to be mentally ill to have an hallucination. The healthy can also see things that aren’t there after taking drugs, being sleep deprived or suffering migraines.
The Australian researchers used a flickering white light against a black backdrop. This induced hallucinations, causing the volunteers to “see” pale grey blobs.
Try this yourself. This is the video used in the study to induce an hallucination:
WARNING: Don’t watch if you have a history of migraines, epilepsy or psychiatric disorders.
Hallucinations are thought to arise when changes in the brain temporarily hijack visual function but the exact causes and mechanisms aren’t fully understood.
“We have known for more than 100 years that flickering light can cause almost anyone to experience a hallucination,” says UNSW Associate Professor Joel Pearson from the School of Psychology.
“However, the unpredictability, complexity and personal nature of these hallucinations make them difficult to measure scientifically.”
Previous studies have relied on drawings and verbal descriptions but these don’t precisely identify the mechanisms in the brain causing hallucinations.
The volunteers for the latest experiment were university students with no history of migraines or psychiatric disorders.
The students watched an image of a plain white ring flicker on and off up to around 130 times per second against a black background.
All reported seeing pale grey blobs appear in the ring and rotate around it, first in one direction and then the other.
“With our technique we get rid of the unpredictability,” says Pearson.
“People don’t see windmills, lines, or different colours; they just hallucinate grey blobs. Once the hallucination is stable like this, with just the blobs, we can start to objectively investigate the underlying mechanisms.”
Pearson says the next step is to investigate whether the experimental methods can be used to model hallucinations produced by psychiatric disorders.
The team has begun working with people with Parkinson’s disease.
“Not everyone who gets Parkinson’s has hallucinations,” says Pearson. “If we can use these models to study their hallucinations, we can find out what might be causing them, and hopefully learn more about other symptoms that accompany natural hallucinogenic states.”
The research is published in the journal eLife.