Lucid Dream
A lucid dream, also known as a conscious dream, is a dream in which the person is aware that he or she is dreaming while the dream is in progress. When the dreamer is lucid, he or she can actively participate in the dream environment without any of the inhibitions or limitations that otherwise would feel natural to persons  who incorrectly believe they are in the "real" waking world.  Lucid dreams can be extremely real and vivid depending on a person's level of self-awareness during the lucid dream.
A lucid dream can begin in one of two ways. A dream-initiated lucid dream (DILD) starts as a normal dream, and the dreamer eventually concludes that he or she is dreaming, while a wake-initiated lucid dream (WILD) occurs when the dreamer goes from a normal waking state directly into a dream state with no apparent lapse in consciousness.
Lucid dreaming has been researched scientifically, and its existence is well established.
Scientists such as Allan Hobson, with his neurophysiological approach to dream research, have helped to push the understanding of lucid dreaming into a less speculative realm.

# Scientific history
The first book on lucid dreams to recognize their scientific potential was Celia Green's 1968 study Lucid Dreams. Reviewing the past literature, as well as new data from subjects of her own, Green analyzed the main characteristics of such dreams and concluded that they were a category of experience quite distinct from ordinary dreams. She predicted that they would turn out to be associated with rapid eye movement sleep (REM sleep). Green was also the first to link lucid dreams to the phenomenon of false awakenings.
Philosopher Norman Malcolm's 1959 text Dreaming argued against the possibility of checking the accuracy of dream reports.
However, the realization that eye movements performed in dreams affected the dreamer's physical eyes provided a way to prove that actions agreed upon during waking life could be recalled and performed once lucid in a dream.  The first evidence of this type was produced in the late 1970s by British parapsychologist Keith Hearne. A volunteer named Alan Worsley used eye movement to signal the onset of lucidity, which were recorded by a polysomnograph machine.
Hearne's results were not widely distributed. The first peer-reviewed article was published some years later by Stephen LaBerge at Stanford University, who had independently developed a similar technique as part of his doctoral dissertation.
During the 1980s, further scientific evidence to confirm the existence of lucid dreaming was produced as lucid dreamers were able to demonstrate to researchers that they were consciously aware of being in a dream state (again, primarily using eye movement signals).
Additionally, techniques were developed which have been experimentally proven to enhance the likelihood of achieving this state.
Research on techniques and effects of lucid dreaming continues at a number of universities and other centers, including LaBerge's Lucidity Institute.

# Research and clinical applications

## Neurobiological model
Neuroscientist J. Allan Hobson has hypothesized as to what might be occurring in the brain while lucid. The first step to lucid dreaming is recognizing that one is dreaming. This recognition might occur in the dorsolateral prefrontal cortex, which is one of the few areas deactivated during REM sleep and where working memory occurs. Once this area is activated and the recognition of dreaming occurs, the dreamer must be cautious to let the dream delusions continue but be conscious enough to recognize them. This process might be seen as the balance between reason and emotion. While maintaining this balance, the amygdala and parahippocampal cortex might be less intensely activated.  To continue the intensity of the dream hallucinations, it is expected the pons and the parieto-occipital junction stay active. To verify this hypothesis, it would be necessary to observe the brain during lucid dreaming using a method such as a PET scan, which captures a snapshot of the blood flow to the brain. No such experiment has yet been performed.

## Treatment for nightmares
People who suffer from nightmares would benefit from the ability to be aware they are dreaming. A pilot study was performed in 2006 that showed that lucid dreaming treatment was successful in reducing nightmare frequency. This treatment consisted of exposure to the idea, mastery of the technique, and lucidity exercises.  It was not clear what aspects of the treatment were responsible for the success of overcoming nightmares, though the treatment as a whole was successful. 
Australian psychologist, Milan Colic, has explored the application of principles from narrative therapy with clients' lucid dreams to reduce the impact not only of nightmares during sleep, but also depression, self-mutilation, and other problems in waking life. Colic found that clients' preferred direction for their lives, as identified during therapeutic conversations, could lessen the distressing content of dreams, while understandings about life - and even characters - from lucid dreams could be invoked in 'real' life with marked therapeutic benefits.

## Perception of time while lucid dreaming
The rate that time passes while lucid dreaming has been shown to be about the same as while waking. In 1985, LaBerge performed a pilot study where lucid dreamers counted out ten seconds while dreaming, signaling the end of counting with a pre-arranged eye signal measured with electrooculogram recording. LaBerge's results were confirmed by German researchers in 2004. The German study, by D. Erlacher and M. Schredl, also studied motor activity and found that deep knee bends took 44% longer to perform while lucid dreaming.

## Near-death and out-of-body experiences
In a study of fourteen lucid dreamers performed in 1991, people who perform wake-initiated lucid dreams (WILD) reported experiences consistent with aspects of out-of-body experiences such as floating above their beds and the feeling of leaving their bodies. Due to the phenomenological overlap between lucid dreams, near death experiences,  and out-of-body experiences, researchers say they believe a protocol could be developed to induce a lucid dream similar to a near-death experience in the laboratory.

# Cultural history
Even though it has only come to the attention of the general public in the last few decades, lucid dreaming is not a modern discovery.
- A very early example of lucid dreaming is in a letter written by St. Augustine of Hippo in 415 AD.
- As early as the eighth century, Tibetan Buddhists were practicing a form of yoga supposed to maintain full waking consciousness while in the dream state.  This system is extensively discussed and explained in the book Dream Yoga and the Practice of Natural Light.  One of the important messages of the book is the distinction between the Dzogchen meditation of Awareness and Dream Yoga. The Dzogchen Awareness meditation has also been referred to by the terms Rigpa Awareness, Contemplation, and Presence. Awareness during the sleep and dream states is associated with the Dzogchen practice of natural light.  This practice only causes lucid dreams as a byproductin contrast to Dream yoga which is explicitly aimed at lucid dreaming. According to Buddhist teachers, the experience of lucidity helps us to understand the unreality of phenomena, which would otherwise be overwhelming during dream or the death experience.
- An early recorded lucid dreamer was the philosopher and physician Sir Thomas Browne (16051682). Browne was fascinated by the world of dreams and stated of his own ability to lucid dream in his Religio Medici: "... yet in one dream I can compose a whole Comedy, behold the action, apprehend the jests and laugh my self awake at the conceits thereof;"
- Marquis d'Hervey de Saint-Denys was probably the first person to argue that it is possible for anyone to learn to dream consciously. In 1867, he published his book Les Reves et les Moyens de Les Diriger; Observations Pratiques (Dreams and How to Guide them; Practical Observations), in which he documented more than twenty years of his own research into dreams.
- The term lucid dreaming was coined by Dutch author and psychiatrist Frederik van Eeden in his 1913 article "A Study of Dreams". This book was highly anecdotal and not embraced by the scientific community. Some consider this a misnomer because it means much more than just "clear or vivid" dreaming. The alternative term conscious dreaming avoids this confusion. However, the term lucid was used by van Eeden in its sense of "having insight", as in the phrase a lucid interval applied to someone in temporary remission from a psychosis, rather than as a reference to the perceptual quality of the experience which may or may not be clear and vivid.
- In the 1950s, the Senoi hunter-gatherers of Malaysia were reported to make extensive use of lucid dreaming to ensure mental health, although later studies refuted these claims.

# Induction methods
Many people report having experienced a lucid dream during their lives, often in childhood. Children seem to have lucid dreams more easily than adults. Although lucid dreaming is a conditioned skill, achieving lucid dreams on a regular basis can be difficult and is uncommon, even with training. Over time, several techniques have been developed to achieve a lucid dreaming state intentionally. The following are common factors that influence lucid dreaming and techniques that people use to help achieve a lucid dream:

### Dream recall
Dream recall is simply the ability to remember dreams. Good dream recall is often described as the first step towards lucid dreaming. Better recall increases awareness of dreams in general; with limited dream recall, any lucid dreams one has can be forgotten entirely.
The main technique used to improve dream recall is to keep a dream journal, writing down any dreams remembered the moment one awakes. An audio recorder can also be very helpful. It is important to record the dreams as quickly as possible as there is a strong tendency to forget what one has dreamt.  It is suggested that for best recall, the waking dreamer should keep eyes closed while trying to remember the dream, and that one's dream journal be recorded in the present tense. Describing an experience as if presently in it can help the writer to recall more accurately the events of their dream.
Dream recall can also be improved by staying still after waking up.  This may have something to do with REM atonia (the condition of REM sleep in which the motor neurons are not stimulated and thus the body's muscles do not move). If one purposely prevents motor neurons from firing immediately after waking from a dream, recalling said dream becomes easier. Similarly, if the dreamer changes positions in the night, they may be able to recall certain events of their dream by testing different sleeping positions.

### Mnemonic induction of lucid dreams (MILD)
The MILD technique is a common technique developed by Dr. Stephen LaBerge used to induce a lucid dream at will by setting an intention, while falling asleep, to remember to recognize that one is dreaming or to remember to look for dream signs when one is in a dream.

### Wake-back-to-bed (WBTB)
The wake-back-to-bed technique is often the easiest way to encourage a lucid dream. The method involves going to sleep tired and waking up five to six hours later. Then, focusing all thoughts on lucid dreaming, staying awake for an hour and going back to sleep while practicing the MILD method. A 60% success rate has been shown in research using this technique. This is because the REM cycles get longer as the night goes on, and this technique takes advantage of the best REM cycle of the night. Because this REM cycle is longer and deeper, gaining lucidity during this time may result in a lengthier lucid dream.

### Cycle adjustment technique (CAT)
The cycle adjustment technique, developed by Daniel Love, is an effective way to induce lucid dreaming. It involves adjusting one's sleep cycle to encourage awareness during the latter part of the sleep. First, the person wakes up 90 minutes before normal wake time until their sleep cycle begins to adjust. After this, the normal wake times and early wake times alternate. On the days with the normal wake times, the body is ready to wake up, and this increases alertness, making lucidity more likely.

### Wake-initiation of lucid dreams (WILD)
The wake-initiated lucid dream "occurs when the sleeper enters REM sleep with unbroken self-awareness directly from the waking state". There are many techniques aimed at entering a WILD. The key to these techniques is recognizing the hypnagogic stage, which is within the border of being awake and being asleep. If a person is successful in staying aware while this stage occurs, he or she will eventually enter the dream state while being fully aware that it is a dream.
There are key times at which this state is best entered; while success at normal bedtime after having been awake all day is very difficult, it is relatively easy after sleeping for 37 hours or in the afternoon during a nap. Techniques for inducing WILDs abound. Dreamers may count, envision themselves climbing or descending stairs, chant to themselves, control their breathing, count their breaths to keep their thoughts from drifting, concentrate on relaxing their body from their toes to their head, or allow images to flow through their "mind's eye" and envision themselves jumping into the image to maintain concentration and keep their mind awake, while still being calm enough to let their body sleep.
During the actual transition into the dream state, one is likely to experience sleep paralysis, including rapid vibrations, a sequence of loud sounds and a feeling of twirling into another state of body awareness, "to drift off into another dimension".

### Induction devices
Lucid dream induction is possible by the use of a physical device. The general principle works by taking advantage of the natural phenomenon of incorporating external stimuli into one's dreams. Usually a device is worn while sleeping that can detect when the sleeper enters a REM phase and triggers a noise and/or flashing lights with the goal of these stimuli being incorporated into the dreamer's dream. For example flashing lights might be translated to a car's headlights in a dream.
A well-known dream-induction device is the NovaDreamer, designed in 1993 by experienced lucid dreamer Craig Webb, now an international speaker/trainer and executive director of The DREAMS Foundation. The NovaDreamer has been discontinued as of 2006. However, a newer version is being worked on, but as of now is not available.
The REM Dreamer is a cheaper and more widely available version of the NovaDreamer. It has one motion sensor in the right eye that is best at recognizing horizontal movement of the eyes. When it picks up the eyes movement it goes through a series of flashing LED lights that filter through into the persons dream and triggers lucidity. Combining this with MILD can be incredibly effective.

### Additional techniques
- Reality tests (as below) practiced in waking life can lead to a test taking place within a dream, leading to the realisation that one is dreaming.
- Meditation and involvement in a conscious focusing on activities can strengthen the ability to experience lucid dreams by making the person more susceptible to noticing small discrepancies of their surroundings.
- There is good reason to believe hypnotic suggestion may help one achieve lucidity. Michael Katz referenced using simple hypnotic induction for the purpose of initiating lucid dreams in his introduction to the first edition of the book Dream Yoga and the Practice of Natural Light.  From the early 1980s, he went on to use this "guided nap" technique during dream yoga and lucid dream training.  He conducts training internationally and maintains an archive of examples.

# Reality testing
Reality testing (or reality checking) is a common method used by people to determine whether or not they are dreaming. It involves performing an action with results that will be different if the tester is dreaming. By practicing these tests during waking life, one may eventually decide to perform such a test while dreaming, which may fail and let the dreamer realize that they are dreaming.
Common reality tests include:
- The nose reality check: Pinch your nose and if you are able to breathe, it's a dream
- Try to stick your finger through the palm of your hand
- Looking at one's digital watch (remembering the time), looking away, and looking back. As with text, the time will probably have changed randomly and radically at the second glance or contain strange letters and characters. (Analog watches do not usually change in dreams, while digital watches have great tendency to do so.)
- Flipping a light switch. Light levels rarely change as a result of the switch flipping in dreams.
- Looking into a mirror; in dreams, reflections from a mirror often appear to be blurred, distorted or incorrect.
- Looking at the ground beneath one's feet or at one's hands. If one does this within a dream the difference in appearance of the ground or one's hands from the normal waking state is often enough to alert the conscious to the dream state.
- Reading text. In a dream, the text in a book may change radically, even while reading. An inability to see the same passage twice is a good indication of a dream.
- Try to turn on a fan, or go somewhere cold; in dreams, people rarely feel wind.
- Try jumping into a lake, bathtub, or any other source of water. If you can breathe, it is a dream.

## Dream signs
Another form of reality testing involves identifying one's dream signs, clues that one is dreaming. Dream signs are often categorized as follows:
- Action  The dreamer, another dream character, or a thing does something unusual or impossible in waking life, such as being able to fly, or noticing photographs in a magazine or newspaper becoming three-dimensional with full movement.
- Powerlessness  There may typically be a sensational loss of bodily strength.
- Context  The place or situation in the dream is strange and includes fictional characters or places.
- Form  The dreamer, another character, or an object changes shape, is oddly formed, or transforms.  This may include the presence of unusual clothing or hair, or a third person view of the dreamer.
- Awareness  A peculiar thought, a strong emotion, an unusual sensation, or an altered perception. In some cases when moving one's head from side to side, one may notice a strange stuttering or 'strobing' of the image.
- Cohesion  Sometimes the dreamer may seem to teleport to another location in a dream, without a noticeable transition.

# Supplements
Several drugs have been shown to improve the probability of a lucid dream occurring and/or increase the length of such a dream:
- Vitamin B6 can increase dream vividness when taken with tryptophan. This is due to the role this vitamin plays in the conversion of tryptophan to serotonin.

# Prolonging lucid dreams
One problem faced by people wishing to lucid dream is awakening prematurely. This premature awakening can be frustrating after investing considerable time into achieving lucidity in the first place.
Stephen LaBerge proposed two ways to prolong a lucid dream. The first technique involves spinning one's dream body. He proposed that when spinning, the dreamer is engaging parts of the brain that may also be involved in REM activity, helping to prolong REM sleep. The second technique is rubbing one's hands. This technique is intended to engage the dreamer's brain in producing the sensation of rubbing hands, preventing the sensation of lying in bed from creeping into awareness. LaBerge tested his hypothesis by asking 34 volunteers to either spin, rub their hands, or do nothing. Results showed 90% of dreams were prolonged by hand rubbing and 96% prolonged by spinning. Only 33% of lucid dreams were prolonged with taking no action.
Once the initial barrier of lucidity is broken, the dreamers next obstacle is the excitement of being conscious within a dream. It is key that the dreamer immediately relaxes upon becoming lucid. There are many methods that work, but in general saturating any of the senses with stimuli from the dream is important. Vision is usually the first sense to fade away, with touch commonly being the last. If the dream starts to fade, you can grab a hold of anything close by, making sure to feel the tactile sensation. Other techniques include shouting in a loud and clear voice, INCREASE LUCIDITY! inside the dream. People are often reluctant to do this, but it significantly stabilizes the dream and increases its vividness. The well-known author, Carlos Castaneda, suggests that the dreamer touch their tongue to the roof of their mouth, an action that greatly increases the realness of the dream.

# Other associated phenomena

## Rapid eye movement (REM)
When a person is dreaming, the eyes move rapidly. Scientific research has found that these eye movements correspond to the direction in which the dreamer is "looking" in his/her dreamscape; this has enabled trained lucid dreamers to communicate whilst dreaming to researchers by using eye movement signals.

## False awakening
In a false awakening, one suddenly dreams of having been awakened. Commonly in a false awakening, the room is similar to the room in which the person fell asleep. If the person was lucid, they often believe that they are no longer dreaming and may start exiting the room and so forth.
This can be a nemesis in the art of lucid dreaming, because it usually causes people to give up their awareness of being in a dream, but it can also cause someone to become lucid if the person does a reality check whenever he/she awakens. People who keep a dream journal and write down their dreams upon awakening sometimes report having to write down the same dream multiple times because of this phenomenon. It has also been known to cause bedwetting as one may dream that they have awoken to go to the restroom, but in reality are still dreaming.
False awakenings can be a great vehicle toward lucidity. The makers of induction devices such as the NovaDreamer and the REM Dreamer recommend doing a reality check every time you awake so that when a false awakening occurs you will become lucid. People using these devices have most of their lucid dreams triggered through reality checks upon awakening.

## Sleep paralysis
During REM sleep the body is paralyzed by a mechanism in the brain in order to prevent the movements, which occur in the dream, from causing the physical body to move. However, it is possible for this mechanism to be triggered before, during, or after normal sleep while the brain awakens. This can lead to a state where a person is lying in his or her bed and he or she feels paralyzed. Hypnagogic hallucination may occur in this state, especially auditory ones. Effects of sleep paralysis include heaviness or inability to move the muscles, rushing or pulsating noises, and brief hypnogogic imagery.  Experiencing sleep paralysis is a necessary part of WILD, in which the dreamer essentially detaches his "dream" body from the paralyzed one.

## Out-of-body experience
An out-of-body experience (OBE or sometimes OOBE) is an experience that typically involves a sensation of floating outside of one's body and, in some cases, perceiving one's physical body from a place outside one's body (autoscopy). About one in ten people has had an out-of-body experience at some time in their lives. Scientists know little about the phenomenon.

# Why we are not always lucid in dreams
Puzzling to many people, given the frequent bizarreness, illogic and dislocation of dreams, is why dreamers are not lucid all of the time.  How can our dreaming selves accept as real so many settings, images and events that in waking life, we assume, would immediately jolt us into disbelief?  The answer to this has been approached in three categories of investigation.
- Depth psychology:  the thrust of personality and psychotherapeutic approaches to this issue suggest that the unconscious dream-work is repressing or inhibiting critical evaluation of the dream in order to perform its salutary function.  Belief in the dream symbols and experience is required for healing, personality integration or catharsis to take place.   Lucidity can only arise if a person is relatively free of un-reconciled conflicts which form barriers.
- Physiology:  seeing is believing to the brain during any mental state.  Even waking consciousness is liable to accept discontinuous or illogical experience as real if presented as such to the brain.   Dream consciousness is similar to that of a hallucinating awake subject.   Dream or hallucinatory images triggered by the brain stem are considered to be real, even if fantastic.    The impulse to accept the evident is so strong the dreamer will often invent a memory or story to cover up an incongruous or unrealistic event in the dream.  That man has two heads! is usually followed not with I must be dreaming! but with Yes, I read in the paper about these famous Siamese twins. 
- Developmental psychology:  this approach suggests that the dream world is not really unnatural after all, since we were all dreaming as children long before we learned of all the physical and social laws that train the mind to a reality.  Fluid imaginative constructions may have preceded the more rigid, logical waking rules and continue on as a normative lifeworld alongside the acquired, waking lifeworld.  The dreaming I basically accepts its world as natural as does the waking I its world.  Dreaming and waking consciousness differ only in their respective level of expectations, the waking I expecting a stricter set of reality rules as the child matures.  The experience of waking up normally establishes the boundary between the two lifeworlds and cues the consciousness to adapt to waking I expectations.  At times, however, this cue is falsea false awakening.  Here the waking I (with its level of expectations) is activated even though the experience is still hallucinatory.  Incongruous images or illogical events during this type of dream can result in lucidity as the dream is being judged by waking standards.  

# Lucid Dreaming in Popular Film
- Waking Life   (2002)
- The Good Night   (2007)
- Vanilla Sky  (2001)
- The Science of Sleep  (2006)