A lucid dream is one in which you're aware of the fact that you're dreaming and can often control what happens. It's a powerful skill to develop for the sake of fun but also as a way to enhance creativity and manage the psychological stressors of waking life. Some people are natural lucid dreamers while others need more practice. One way to increase your chances of having a lucid dream is to regularly ask yourself if you're dreaming. The idea is that if you get into the habit of questioning the reality of your phenomenal experience while awake, you'll also do it while dreaming, thereby triggering lucidity. Now, Radboud University Medical Centre neuroscientists and their colleagues have shown that virtual reality can be an effective training tool for lucid dreaming. According to the researchers, spending waking time in surreal environments (such as provided by VR) inspires us "to question one's reality" with more frequency and focus. Always a good thing to do, I'd say. From Philosophical Transactions of the Royal Society B:
Lucid dreaming has been shown to occur with stronger dream control in patients with bipolar disorders and schizophrenia[…] which include dissociative and depersonalization-like symptoms as part of their central pathology. It could accordingly be argued that dissociative symptoms related to VR might instil a sense of 'dissreality' and 'reality scepticism' that increased the authenticity of reality checks. In other words: it could well have been a potential post-VR dissociative state that was 'dream like', rather than the VR content itself, supporting the initial premise of the study, albeit through serendipitous and unforeseen secondary consequence of the primary intervention.
It therefore stands to reason that the tentative gains seen in the VR group could be explained through a combination of several overlapping factors: dream-like VR scenarios provided a training ground for metacognitive reflections; bizarre and novel VR content was subsequently incorporated into participants' dream imagery; and this reminded them of the study goal when noticed. It is further worth considering whether the VR experience itself could have exerted some dissociative effects, which postspectively provided a fertile and convincing (dream-like) psychological state from which to question one's reality, as part of the required lucid dreaming training.