It seems like every time researchers look further into our sensory-perceptive systems, we have another hole punched in our certainty that what we think we're perceiving is actually real.
We've looked at optical illusions -- and the fact that dogs fall for 'em, too. We've considered two kinds of auditory illusions, the postdictive effect and the McGurk effect. Sometimes we see patterns of motion in still objects -- and illusory "impossible" motion that our brains just can't figure out. A rather simple protocol convinced test subjects their hands had turned to stone. Stimulating a particular clump of neurons in the brain made patients see the doctor's face as melting. We can even be tricked into feeling like we're controlling a second body, that just happens to be invisible.
As eminent astrophysicist Neil deGrasse Tyson put it, "The human brain is rife with ways of getting it wrong." Honestly, at this point it's a wonder we trust anything we perceive -- and yet you still hear people say "I saw it with my own eyes" as if that somehow carried any weight at all. Add to that all the problems with the reliability of memory, and you have to ask why eyewitness accounts are still considered the gold standard of evidence.
If you needed more proof of this, take a look at some research that came out last week from Ruhr-Universität Bochum into what happens when a person watches a virtual-reality avatar of their own body. Participants were suited up in VR gear, and after a period of acclimation -- during which they got used to their avatar's arms and hands moving as their own did -- they were instructed to use a virtual representation of a stick to touch their avatar's hand. Nearly all of the subjects reported feeling a sensation of touch, or at least a tingling, at the spot the virtual stick appeared to touch.
The researchers decided to check and see if the sensation occurred simply by drawing awareness to the hand, so they did the same thing only using a virtual laser pointer -- and no feeling of touch occurred.
Apparently all it took was convincing the subjects they were being touched to stimulate the sensation itself."The phantom touch illusion also occurs when the subjects touched parts of their bodies that were not visible in virtual reality," said study co-author Marita Metzler. "This suggests that human perception and body sensation are not only based on vision, but on a complex combination of many sensory perceptions and the internal representation of our body."