Wednesday, November 30, 2022
Nov. 30, 2022

Linkedin Pinterest

Scientists trick subjects into feeling invisible

Virtual reality headset employed to create illusion

The Columbian

VIDEO: Creating phantom-limb syndrome in non-amputees.

Your brain’s sense that your body is your body is something you probably take for granted. But new research shows that in just seconds, your brain will readily accept a full-body illusion as truth. Even if that illusion is that your entire body has turned invisible. And the spooky research that proves it might help develop treatments for social anxiety.

In a new study published Thursday in Scientific Reports, a team of neuroscientists from Sweden’s Karolinska Institutet used a virtual reality rig to convince their subjects of just that.

The researchers were building on previous work where they’d induced phantom limb syndrome — the sense that a missing limb is there in the empty space — in non-amputees. In essence, the subjects were unconsciously convinced that their arm was actually in front of them and invisible when it was really hidden behind a screen. Doctoral student Arvid Guterstam, who took the lead on the latest study, describes the previous experiment here:

“We wondered if it was possible to generalize this sense of an invisible limb to an entire invisible body using the same psychological trick,” Guterstam said.

To scale up the experiment, they put their subjects into virtual reality headsets and placed two cameras at eye level, pointing down, in another part of the room. When the subjects put their headsets on and looked down at themselves, they saw empty space where their body should have been.

VIDEO: Creating phantom-limb syndrome in non-amputees.

But that wasn’t enough to make them feel invisible – either by their own description or through objective tests designed to trick their subconscious.

To do that, the researchers touched the subjects with large paintbrushes while making corresponding touches in the region of empty air they were looking at. So if a subject’s torso was brushed, someone would make sure they saw a brush moving at the same time and in the same direction right about where their “invisible” torso would be in space.

When the brush motions weren’t synced up, the subjects maintained their sense of self. But when they were, it didn’t take long at all for the subjects’ minds to play tricks on them. Around 70 percent of the subjects seemed to have accepted the illusion.

“One way we tested this was to subject the portion of empty space to physical threats,” Guterstam explained. “We’d have a kitchen knife enter the field of vision and make stabbing motions at the invisible body while we measured heart rate and sweat in the subject. When the illusion had been created, there was an elevated sweat skin response, and a higher heart rate, as if their brains were interpreting this threat in empty space as a threat to their own body,” he said.

Now that he’s sure that one can be made to feel invisible, he’s excited to see what that illusion does to the brain. Some have suggested that a sense of invisibility would make humans act less morally, because on some level they’d lose their fear of societal repercussions for their actions. That would certainly be something to keep in mind as the military works on creating “invisibility cloaks” for soldiers.

Support local journalism

Your tax-deductible donation to The Columbian’s Community Funded Journalism program will contribute to better local reporting on key issues, including homelessness, housing, transportation and the environment. Reporters will focus on narrative, investigative and data-driven storytelling.

Local journalism needs your help. It’s an essential part of a healthy community and a healthy democracy.

Community Funded Journalism logo