Lucid dream
Lucid dreaming is the ability to consciously recognize, perceive and modify the dream state. "Lucid" dreamers report being able to freely remember the circumstances of waking life, to think clearly, and to act deliberately upon reflection, all while experiencing a dream world that seems vividly real.
Most persons have at least one lucid dream during their life, often in their childhood. However even with training, achieving such a dream state on a regular basis is uncommon. Lucid dreams are notable for their durability in memory, exceptionally more so than with regular dreams. Lucid dreamers regularly describe their dreams as exciting, colourful and fantastic (in the literal sense), and often compare their dream to a spiritual experience.
Despite the difficulty of achieving a lucid dream on a regular basis, techniques have been developed to achieve the state intentionally. A number of universities conduct research into both the condition and these techniques (notably Stanford), as do some independent agencies such as The Lucidity Institute. At present there are no known cases where lucid dreaming has caused damage on either the psychological and physiological level.
One method of testing whether not one is dreaming or not is to read a text look away and read it again. In the real world the text will not change, while in a dream, the text will often change.
History of lucid dreaming research
The term "Lucid dreaming" was coined by Frederik van Eeden in his book A Study of Dreams (1913). This book was a higly personal account and not embraced by the scientific community, and the possibility of achieving such a lucid dream state was dismissed categorically by N Malcolm in his 1959 text Dreaming. The enthusiastic endorsement of lucid dreaming during the 1970's by New Age proponents such as Carlos Castaneda did little to enhance its scientific credibility.
However during the 1980's credible scientific evidence to confirm the existence of lucid dreaming was produced, [1], and lucid dreamers were able to demonstrate to researchers that they were consciously aware of being in a dream state (usually by performing a pre-arranged series of physical cues such as distinct patterns of eye movement [2]). Additionally techniques were developed which have been experimentally proven to enhance the likelihood of achieving this state [3].
One outstanding question on the neurophysiogical nature of lucid dreaming concerns the electrical activity in the frontal cortex, which is generally suppressed during normal sleep. The behaviour of the frontal cortex has not at present been analysed with regard to lucid dreaming.
Some psychologists have theorised that the intensely "real" experience of lucid dreaming may actually provide a valid explanation for accounts of alien abduction, Astral travelling and other paranormal, "out-of-body" experiences. [4]
There is a substantial cottage industry based around the technique of lucid dreaming, with an array of devices (usually based around flickering light arrays) commercially available to (allegedly) enhance achievement of this state. Likewise, its proponents argue that it help achieves a higher level of spiritual consciousness, and associate it with other New age concepts such as Astral travelling or Dream sharing. Regardless, this has no impact on lucid dreaming's stature as a scientifically verified phenomenon.