We may find it hard to come to terms with the fact that our normal waking experience of reality is a manifestation within the mind, but in many other instances we readily accept that we create our experiences.
A classic example of reality creation that has long fascinated medical researchers is the phantom limb phenomenon. A person who has lost an arm or leg may continue to have sensations that seem to come from the missing limb. For some reason the nerve fibers that once reached down into the leg or arm, although no longer connected to any sensory receptors, are still sending signals to the brain. The brain construes these impulses as if the limb were still there and creates the corresponding experience. this can be most disconcerting for the person concerned, who may feel an irresistible to scratch an itch in an arm or leg that isn't there.
The opposite phenomenon can occur in situations in which the body has become unusually still. Arms and legs that are definitely there in the physical world can completely disappear from experience. Normally we know where our arms and legs are, even when not looking at them or touching them, because any bodily movement, however slight, triggers impulses in the bodies proprioceptors. These are sense receptors located in joints, muscles, the skin, and other organs that inform the brain of changes in position, tension and suchlike in the internal organs. When the body becomes very still, as can happen in states of deep mediation, these proprioceptors may no longer be triggered and flow of data from them can die away. The brain no longer has the necessary information from which to construct its image of the body, and so the arm or leg ceases to exist„in awareness that is. Conversely, it only takes a minute movement„a flexing of one's little toe, say„to trigger a flow of proprioceptive data, and the missing arm or leg immediately returns to awareness.
A more familiar example of how we create our experience of reality occurs in so-called visual illusions. Here the sensory information is either ambiguous or misleading, and the image constructed by the brain no longer corresponds to reality. A very, but powerful, example that we have probably all come across is the drawing below. Is it a cube seen from above, or from below? The most common first response is "from above"; that is probably because in daily life we are far more used to seeing rectangular corners from above„tables, boxes, TV sets, filing cabinets. It is not so often that we look up at such things from underneath. But if you put your attention on the top right corner, and bring that forward in your mind's eye, you can probably change your perception to that of a cube seen from below.
What is most interesting about this example is not that the picture is ambiguous, but the way in which different three-dimensional realties are created from it. All you are actually seeing is twelve lines on a flat sheet of a paper. A cube, whether seen from above or below, is an interpretation you have imposed on the data. But, and this is the fascinating part, that interpretation appears real. Whichever way you see it, from above or below, you experience a three-dimensional object; there is a depth to it, and this depth is something that you have added. It is very real, but only in your mind.