Lucid dream induction by visual and tactile stimulation: An exploratory sleep laboratory study
In a lucid dream the dreamer is aware of the dream state. Previous research has shown that external stimuli (e.g. flashing lights) presented to a person during REM sleep can trigger lucidity. To further examine the possibility of lucid dream induction by external stimulation, visual and tactile stimuli were investigated in an exploratory sleep laboratory study.
In the first experiment 10 participants spent two none-consecutive nights in a sleep laboratory. In the first night a visual stimulus (flashing lights) was presented during REM sleep and in the second night tactile stimulation (vibration) at the index finger was utilized, again in REM sleep. In the second experiment 14 participants spent a single night in the sleep laboratory and tactile stimulation (vibration) either at the wrist or at the ankle was applied during REM sleep. The participants were instructed to perform two consecutive left-to-right eye movements to indicate lucidity in the dream.
Light stimulation yielded one signal-verified lucid dream out of 18 application trials (5.6 %) whereas tactile stimulation at the index finger did not provoke any lucid dream at all (21 applications). Tactile stimulation at the wrist or ankle resulted in two signal-verified lucid dreams out of 27 trials (7.4 %). Stimuli were incorporated in 38.9 %, 42.9 %, and 55.6 % of stimulations, respectively.The results suggest that lucid dreams might be triggered by visual or tactile stimulation. However, the frequencies of the induced lucid dreams are – in comparison to earlier studies – quite low. Furthermore, for tactile stimulation it seems important at which part of the body the stimulation is applied. In general, the intensity of stimulation needs to be adjusted because stimulation often led to an awakening of participants. Thus it seems important for future studies to focus on factors like waking thresholds and preparation of participants in order to minimize awakenings and to maximize lucid dream induction.