A lucid dream is a dream during which the dreamer is aware of dreaming. During lucid dreaming, the dreamer may be able to exert some degree of control over the dream characters, narrative, and environment.
In 1968, Celia Green analyzed the main characteristics of such dreams, reviewing previously published literature on the subject and incorporating new data from participants of her own. She concluded that lucid dreams were a category of experience quite distinct from ordinary dreams, and 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.
Lucid dreaming was subsequently researched by asking dreamers to perform pre-determined physical responses while experiencing a dream, including eye movement signals. The first peer-reviewed article on the subject was published by Stephen LaBerge at Stanford University, who developed such techniques as part of his doctoral dissertation. In 1985, LaBerge performed a pilot study that showed that time perception while counting during a lucid dream is about the same as during waking life. Lucid dreamers counted out ten seconds while dreaming, signaling the start and the end of the count with a pre-arranged eye signal measured with electrooculogram recording.
Neuroscientist J. Allan Hobson has hypothesized what might be occurring in the brain while lucid. The first step to lucid dreaming is recognizing 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 continue but be conscious enough to remember that it is a dream. 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.
Using electroencephalography (EEG) and other polysomnographical measurements, LaBerge and others have shown that lucid dreams begin in the REM stage of sleep. LaBerge also proposes that there are higher amounts of beta-1 frequency band (13–19 Hz) brain wave activity experienced by lucid dreamers, hence there is an increased amount of activity in the parietal lobes making lucid dreaming a conscious process.
Some skeptics of lucid dreaming suggest that it is not a state of sleep, but of brief wakefulness, or "micro-awakening".
Paul Tholey, a German oneirologist and Gestalt theorist, laid the epistemological basis for the research of lucid dreams, proposing seven different conditions of clarity that a dream must fulfill in order to be defined as a lucid dream:
- Awareness of the dream state (orientation)
- Awareness of the capacity to make decisions
- Awareness of memory functions
- Awareness of self
- Awareness of the dream environment
- Awareness of the meaning of the dream
- Awareness of concentration and focus (the subjective clarity of that state).
Later, In 1992, a study by Deirdre Barrett examined whether lucid dreams contained four "corollaries" of lucidity:
- The dreamer is aware that they are dreaming
- Objects disappear after waking
- Physical laws need not apply in the dream
- The dreamer has a clear memory of the waking world
Barrett found less than a quarter of lucidity accounts exhibited all four.
Subsequently, Stephen LaBerge studied the prevalence of being able to control the dream scenario among lucid dreams, and found that while dream control and dream awareness are correlated, neither requires the other. LaBerge found dreams that exhibit one clearly without the capacity for the other; also, in some dreams where the dreamer is lucid and aware they could exercise control, they choose simply to observe.
There’s an ongoing lucid dreaming research in the Lucidity Institute. The research team states that “Lucid dreaming is an extraordinary and powerful state of consciousness accessible to all people”. There’s a possibility to contribute to ongoing lucid dream research by participating in the experiments on Lucidity Institute's website.