How deep is the rift between conscious states in sleep and wakefulness? Spontaneous experience over the sleep–wake cycle

The conventional view that sleep and wakefulness mark a sharp divide in conscious experience is challenged by recent research showing that mind wandering occupies much of waking life and that dreaming resembles intensified mind wandering. This suggests a continuum of spontaneous experience spanning both states. A conceptual framework distinguishing subtypes of spontaneous thoughts and experiences independently of behavioral state is proposed and applied to findings from dream and mind-wandering research. The argument holds that assessing the relationship between spontaneous experience and sleep or wakefulness requires looking beyond dreams to include dreamless sleep-related experiences. Considering the full range of spontaneous thoughts and experiences reveals variation both within and across behavioral states, undermining the coarse-grained distinction between sleep and waking and their assumed link to conscious states.

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Abstract

Whether we are awake or asleep is believed to mark a sharp divide between the types of conscious states we undergo in either behavioural state. Consciousness in sleep is often equated with dreaming and thought to be characteristically different from waking consciousness. Conversely, recent research shows that we spend a substantial amount of our waking lives mind wandering, or lost in spontaneous thoughts. Dreaming has been described as intensified mind wandering, suggesting that there is a continuum of spontaneous experience that reaches from waking into sleep. This challenges how we conceive of the behavioural states of sleep and wakefulness in relation to conscious states. I propose a conceptual framework that distinguishes different subtypes of spontaneous thoughts and experiences independently of their occurrence in sleep or waking. I apply this framework to selected findings from dream and mind-wandering research. I argue that to assess the relationship between spontaneous thoughts and experiences and the behavioural states of sleep and wakefulness, we need to look beyond dreams to consider kinds of sleep-related experience that qualify as dreamless. I conclude that if we consider the entire range of spontaneous thoughts and experiences, there appears to be variation in subtypes both within as well as across behavioural states. Whether we are sleeping or waking does not appear to strongly constrain which subtypes of spontaneous thoughts and experiences we undergo in those states. This challenges the conventional and coarse-grained distinction between sleep and waking and their putative relation to conscious states. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.