All subjects were asked to fill out two types of questionnaires: a questionnaire filled out before the first night, and a second questionnaire filled out after every night.
The questionnaire filled out before the first night revealed that no subject knew any Morse code signals before the experiment, apart from the Morse code “SOS” which two subjects knew beforehand. Two subjects stated to make use of reality testing (“reality checks”) in order to increase the probability of lucid dreaming, one subject claimed to have used this method but to have stopped using it, one subject does not use any lucid dreaming techniques at all and one subject uses the technique of falling back into a previously dreamed dream after waking up. On the question whether the subjects have regularly occurring dream contents, three subjects could name some, for example flying out of the bedroom window. This question aimed at finding dream contents that might help the subjects to realize that they are dreaming (“next time I fly through a bedroom window I realize that I am dreaming”), especially for the MILD and WBTB method used during the second night. However, none of the few reported regularly occurring dream contents were reported in any of the dream reports during the experiments and thus, could not help with increasing lucid dream probability.
The questionnaires filled out every morning after finishing the sleep experiment show that the overall sleep quality (measured using the German school grading system, from 1: very good to 6: insufficient) was quite poor in the first night (average of 4), however, became much better in the second and third night (average of 2). Subjects explained the poor first night sleep quality by the unfamiliar sleep experiment situation and the unfamiliar environment. Surprising is that the PSG recordings taking place during the second night, which were thought to disturb normal sleep behavior much more than the simple Zeo headband, were not reported as worsening the sleep quality. All subjects complained about the heat in the sleep lab, especially since there was no possibility to open a window. Some of the subjects complained about the sound of the ventilation system. All subjects stated that the tones of the experiment had negative impact on their sleep quality, which is not surprising since the subjects were woken up by the tones multiple times. Nevertheless, all subjects found the experiment interesting and exciting, and three of the five subjects even stated that they enjoyed the experiment and would like to participate in follow-up studies.