Ask any first grader to name the five senses and sight, hearing, touch, smell, and taste will roll out as a satisyfying answer. But this list leaves off the sense of balance, along with body position. We generally don't think of this sense because it is always on. We close our eyes and it gets dark, but we still know which way is up and what our bodies are doing. Gravity feels like a constant force of nature, and we feel firmly rooted in our bodies.
The key word here is feel. As much as we may take it for granted, there is a true sensory process going on, involving the vestibular organs of the inner ear, the positional information coming from our joints, as well as integration of other sight and touch cues. And since it is a sensory process, it can be manipulated to induce an illusion. Neuroscientists have used surprisingly low-tech methods involving virtual reality goggles and a stick to create an out-of-body sensation in ordinary people.
This experiment reminds us that the most basic feeling in the world, of existing in our own bodies, is constructed by multiple sensory streams and is under some circumstances open to interpretation.
Once we understand this sensory process, we will surely find ways to manipulate it. Will we have virtual reality goggles in the near future that allow us to truly feel like we are flying, or observe ourselves from a distance, seeing ourselves as others do? (A truly terrifying option, in my opinion.) The possibilities for a sense of total liberation or self-conscious social paralysis are interesting to consider.
If we develop disembodied experiences, how will that change the way we think about ourselves, and the world? I have already wondered how the experiences of teleporting, flying, and changing the camera view in virtual worlds such as Second Life may affect the way we view real life. In ten years, will my teenage daughter be saying, "Geez Mom, you are so lame. You don't even understand what it means to fly!"
Things could always get weirder. Recently a philosopher from Oxford University suggested that our universe may be a computer simulation similar to "The Matrix." Put it all together and it's enough to make anyone whoa like Keanu Reeves.