Dreaming Continued.Other methods of testing reality are:
- Look at your hands. Study them for a moment and make sure they're yours. If you look at your hands in a dream, it will very likely bring lucidity, and/or your hands will look wrong and alert you that you're dreaming. Hands are considered a gateway because our brains are always exquisitely aware of the position of our hands.
- The Zen method of bringing about lucid dreaming: Stop and ask yourself regularly during the day, "Am I dreaming?" Just look around and ask yourself if you're dreaming. (If you have trouble answering the question, you may want to look below!) Sooner or later you will, out of habit, look around in a dream and ask yourself if you're dreaming. Often this is all it takes to "wake up" during a dream and achieve lucidity.
- Pinching yourself is a popular method, but when it has results, they usually come from the fact that while pinching yourself, you're asking yourself if you're awake. Simply feeling physical pain isn't an indicator of anything, since dreams often "feel" quite real.
- Do something that you know has to have a certain result, independent of you. For instance, if there are birds nearby, yell or wave your arms at them. Throw a snowball against a wall. Jump high in the air and wave your arms. You know what should happen in each of these cases -- the birds will fly away, the snowball will detonate into bits, and you'll land on the ground after being airborne for only a few feet. If you're dreaming (or hallucinating), the results may be abnormal.
Psychology. However, these methods are not only useful in dream-experiments. Reality-testing is also a somewhat slangy term used in psychology to refer to a person's ability to determine that they're not dreaming when they're wide awake. It's a very important concept, because its presence delineates the difference between someone who is psychotic and someone who is not. Psychosis is, in fact, the technical term for "having lost the ability to reality-test". Psychosis is considered a symptom in psychology, like a fever, rather than a diagnosis, and it is not an all-or-nothing condition. Many psychologists recommend teaching patients who are under high stress or otherwise prone to psychosis some of the above reality-testing methods to help them "keep their feet" if or when they feel uncertain about reality.
Someone can be hallucinating and still retain the ability to reality-test, however. (This is why reality-testing, not the presence of hallucinations, is what defines psychosis.) A person may realize that they are hallucinating, though unfortunately, unlike in dreams, successful reality-checking does not always end a hallucination, especially if the hallucination is caused by an external factor such as drugs or illness. Other coping measures are sometimes necessary.
Consciousness Theory.Many mental illnesses allow the sufferer to retain reality-testing, but people generally understand the most serious ones to remove this ability. People who are completely delirious, severely schizophrenic, extremely paranoid and catatonic have all lost the ability to determine what is and isn't reality. Besides the medical connotations, there are questions raised by these illnesses about the nature of consciousness, and whether someone who appears awake and even mobile, but who can't respond to reality in any functional way, is really a conscious human being. The argument is often made that (for instance) a badly-off schizophrenic is surely conscious, because even if he or she can't reality-test now, s/he might be brought back, might regain their reality-testing ability, in the future. However, a provocative counterargument exists, since we do not consider people in a coma to be conscious, yet they, too, might eventually be brought back. The central question seems to be whether reality-checking is the key marker for consciousness, or whether things like being able to walk and talk are more important.
Sources: Wikipedia entry on Psychosis: http://en.wikipedia.org/wiki/Psychosis
And course materials on Consciousness Theory, best summarized in the book "The Mind's I" by Douglas Hofstadter and Daniel C. Dennett.