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.… Read more