In their piece, Voss and Hobson consider the latest empirical evidence on lucid dreaming and set forth four hypotheses that, they suggest, would begin to explain the whys and the hows of lucid dreaming. The four hypotheses proposed—the BMH (Brain Maturation Hypothesis), the GBH (Gamma Band Hypothesis), the HSH (Hybrid State Hypothesis), and the SCH (Space of Consciousness Hypothesis)—are based on five years of scientific research on lucid dreaming and, together, are meant to provide a multi-faceted picture of what lucid dreaming is, how it arises, why it arises, and how it relates to other states of consciousness.
The first hypothesis they propose is the BMH (Brain Maturation Hypothesis), which serves as a potential explanation for why there is lucid dreaming. Evidence shows that lucid dreaming occurs naturally and most often during certain periods of brain development and maturation in children and young adults.[2] The empirical evidence also suggests that lucid dreams are peculiar mental states that occur during the final stages on frontal lobe integration and, as such, are “nothing but an accidental confounding of conscious states during a time of high cerebral diversification” (Voss & Hobson this collection, p. 8). For these reasons, Voss & Hobson hypothesize that “during childhood and puberty, frontal lobe activity is sometimes decoupled from the arousal state so that frontal lobes can become active in a state for which this type of activity is untypical”—the BMH (this collection, p. 8). This, they propose, explains why lucid dreaming occurs.
Voss and Hobson then offer three other hypotheses—GBH, HSH, and SCH—as explanations of how lucid dreaming occurs. The GBH (Gamma Band Hypothesis) provides an account of how lucid dreaming arises by appealing to specific changes in brain activity associated with the onset of a lucid dream during ongoing REM sleep. Specifically, this hypothesis holds that the principle brain correlate of lucid dreaming is 40Hz activation of the frontal cortex—activation at this frequency brings about the meta-awareness associated with secondary consciousness. The HSH (Hybrid State Hypothesis) & SCH (Space of Consciousness Hypothesis) shift away from particular brain activity and, rather, provide a brain-based explanation and classification, respectively, of what lucid dreaming is in relation to other mental states. The HSH suggests that lucid dreaming involves elements of both waking and dreaming consciousness, and is, indeed, a destabilized hybrid state involving both frontal cortex activation, as suggested by the GBH, and REM sleep cortical activation. The HSH explains the how of lucid dreaming by offering a way to reconcile the subjective reports of lucid dreamers with the empirical data of cortical activation. The SCH lays out a three-dimensional model with which to categorize various states of consciousness and to see how the spectrum of mental states relate to one another along certain variables. This model allows us to situate lucid dreaming within a state space of consciousness and ascertain the similarities it might hold with other waking states of consciousness. These four hypotheses work together to consolidate the quantitative and qualitative data on lucid dreaming and provide a picture of why and how lucid dreaming occurs. For my purposes here, I will set aside the BMH and the GBH and will instead return to the HSH and the SCH in sections 4 and 5.
Importantly, the authors specify that their interest lies in considering REM-sleep lucid dreaming. In other words, the focus of their paper is to consider cases where the dreamer correctly achieves insight into the fact that he or she is dreaming while the dream continues (see Voss & Hobson this collection, p. 4). The authors appeal to the Lucidity and Consciousness in Dreams Scale (LuCiD) they developed to assess the various features of a lucid dream state, and with this they describe eight features of lucid dream consciousness: insight, realism, control, memory, thought, positive emotion, negative emotion, and dissociation.[3] Of these eight factors, three are highlighted as particularly important to the study of lucid dreaming—insight, control, and dissociation—as they do not typically appear in non-lucid dreams.[4] The core criterion of lucid dreaming, however, appears to be insight. This feature, once it appears, then causally enables the possibility of control and dissociation. One of the issues that I will explore further in the next section is whether insight should be thought of as an epistemic or a phenomenal state, and what either of these interpretations might mean for understanding the role of insight in lucid dreaming.
Most of Voss and Hobson’s article discusses the features of insight and dissociation in relation to recent empirical evidence, and although there is indeed very illuminating discussion of these features, I nonetheless think there is still much conceptual confusion and semantic vagueness with regard to what exactly they are and how they relate to our non-dreaming conscious states. As I show in the next section, this is where philosophical considerations can help clarify the conceptual landscape and help move the empirical project forward.