You’re standing in a VR world, surrounded by virtual grass. The wind whips up and blows through the field, and as you watch the tall grass blowing in the wind, you can feel it buffet your body; how is this possible?
Episode 1: The Phantom Sense
When you’re in VR and you can “feel” a sensation that’s not actually produced by the hardware, it’s referred to as “phantom sense“, which may sound like the “phantom pain” that amputees experience you’ve probably heard about before. Still, it’s quite different once you consider how phantom sense likely works.
Phantom sense in VR isn’t a new discovery, but now that VR headsets are going mainstream members of the public are discovering this phenomenon for themselves. If you search forums such as Reddit for the term “phantom sense”, you’ll see numerous accounts from VR users who claim to experience it.
For many VR users, this type of ‘bonus” immersion is desirable, so many of those aforementioned forum posts are actually about how to induce phantom sense, with different VR fans offering a variety of advice on how to make it happen. Whether any of those methods work is debatable, but can something like “phantom sense” really happen, and how does it even work?
Perception Is “Top-Down” and “Bottom-Up”
Humans and other living things “perceive” the world around us with sense organs. In school, you’re taught that there are five senses, but the truth is that you have many different senses that give your brain information about the outside world and the state of your body.
Perception is a complex process that’s both “top-down” and “bottom-up” in nature. The bottom-up part of perception is the raw information that’s going from your eyes, ears, and other sense organs to your brain. In your brain, that information is processed into something that makes sense to your conscious mind. So, what you perceive isn’t actually reality but a processed version of it that makes sense from a human perspective.
Top-down aspects of perception are things like your previous experience and what you’ve learned about the world. Your expectations and prior knowledge let your brain automatically fill in the blanks or predict what it thinks you should be seeing. Magic tricks and optical illusions often take advantage of your expectations and how they influence what we see and hear. It’s most likely between these two types of perceptual processing that phantom sense happens.
Phantom Sense in the Lab
The phantom sense that people report experiencing in VR is most likely a form of “body transference”. Body transference happens when someone takes “ownership” of something as part of their own body when it isn’t. The classic experiment involves a rubber arm attached to the subject so that it’s in the position you expect your real arm to be.
Stroking the arm has been shown to induce that sensation in the subject. Similarly, sticking a needle into the rubber arm can induce pain. Psychologists theorize that this illusion happens when bottom-up processes override top-down processes. In other words, even though you know it’s not your real body part, on a fundamental your brain is fooled into accepting it and your conscious mind is along for the ride whether it wants to be or not.
Adding on to this, VR has been deliberately used to induce body transference. Researchers have determined that a person’s VR body induces the same threat response as it would in real life. In other words, under the right conditions, the brain accepts ownership of the virtual body, and the radical body transference illusion occurs. This might explain why some VR users experience phantom senses.
What Does This Mean for VR?
Much of our media depends on our perceptual systems’ ability to fill in the gaps. That’s why you perceive motion instead of scrolling still images in a movie theater or only need the simplified suggestion of something in a painting to perceive the whole picture.
If VR developers could tease out the factors that reliably induce phantom sense (much like they did for “presence” in VR), it could become another tool for VR authors to use when creating experiences.
Unfortunately, there’s also a dark side to phantom sense since negative perceptions are possible alongside positive ones. The idea that VR could be used for dubious interrogation practices is something that’s given ethicists pause for some time now, and phantom sense could be a sad part of that formula if anyone figures out how to use it deliberately.
Then again, a little like lucid dreaming, if you can teach or train yourself to experience phantom sense in VR, it has the potential to elevate your VR experience beyond mere hardware. Or you can think of it as using the “wetware” in your brain to make VR more immersive than ever.