We spend roughly one third of our lives asleep, and research tells us that a considerable portion of this time is spentdreaming. Yet, most of us rarely remember our dreams, and even when we do, we would be hard-pressed to de-scribe more than a single dream per night. This paucity of spontaneous dream recall stands in marked contrast tothe diverse kinds of dreams and other types of cognitive activity that participants report following timed awakeningsin the sleep laboratory. Scientic sleep and dream research are now producing a steady stream of empirical data,and it stands to reason that this research will have a profound impact on scientic and philosophical theories ofconsciousness and the self. Yet, in order to make sense of these results, a comprehensive framework for describingconscious experience in sleep and dreams is needed.

Providing the outlines of such a framework is the goal of Dreaming. In this series of blogposts, I will address a numberof questions that I take to be particularly pressing for an empirically informed (and hopefully also empirically infor-mative) philosophical theory of dreaming. I start out by giving a brief and highly selective overview of changing con-

CONSCIOUSNESS, DREAMING, JENNIFER WINDT: DREAMING, PSYCHOLOGY

(RE-)MAPPING THE CONCEPT OF DREAMINGJULY 5, 2015 | JENNIFER WINDT | 1 COMMENT

The Brains Blog

ceptions of sleep and dreaming in scientic research and in philosophy.

The elusiveness of dream recall is paralleled by shifts in scientic and philosophical theorizing about sleep anddreaming. The most well-known of these are Freudian dream theory, which casts dreaming as a carefully disguisedand censored form of wish-fulllment, and the discovery of REM sleep in the 1950s, which marked the beginning ofthe scientic investigation of dreaming, but also of sleep (for an excellent overview, see Kroker 2007). But both be-fore and after these paradigmatic shifts, dream theories, and with them the concepts of sleep and dreaming, under-went various adjustments and renements. While the ancients viewed dreams as messages from the gods, Aristotle,in his treatise On Dreams, provided the rst strictly naturalistic theory of dreaming: dream imagery was, he thought,linked to the residual movements of the sensory organs during sleep. Like reections in a pool of water, these move-ments were clearest in the quiet of deep sleep, which consequently gave rise to the clearest types of dream imagery.Dreaming was, in a sense, the after-effect of waking perception, and sleep, quite simply, the absence of wakefulness.This basic idea of sleep and waking as opposites persisted all the way into the 20 century, where sleep was com-monly regarded as a uniform period of reduced brain activity, a state in which we are, largely, dead to the world.

In the 1950s, the discovery of a period of sleep characterized by wake-like activation of the EEG, near-completemuscular paralysis and rapid eye movements (hence the term REM sleep) revolutionized scientic conceptions ofsleep. Sleep was now seen to have a complex architecture, consisting of periodic transitions through different stagesof sleep. It was also thought that dreaming could be assigned its own sleep stage, rather than occurring throughoutsleep. In general, participants in sleep laboratory studies report dreams following almost 80% of awakenings fromREM sleep, but do so much more rarely when awakened from the stages of NREM (or non-REM) sleep (Nielsen2000). This combination of rich subjective experience and high-levels of brain activity in the absence of behavioralresponsiveness and the outward signs of behavior initially seemed paradoxical (indeed, REM sleep is sometimes alsocalled paradoxical sleep). It strongly contradicted behaviorist sentiments and seemed to suggest that the occur-rence of dreaming could be objectively measured and even predicted based on polysomnographic measurementsobtained during REM sleep (see for instance Dement & Kleitman 1957). This development threatened to dethronesubjective dream reports, which so far had been the sole arbiter of whether a dream had been experienced or not.

The result was a tug-of-war between philosophical dream theories and the developing eld of scientic dream re-search. Norman Malcolm (1956, 1959) famously declared that the very attempt to study dreams scientically, inde-pendently of and perhaps even in contradiction to subjective dream reports, was a conceptual absurdity: Dreamsoccur in sound sleep, and if a person is in any state of consciousness it logically follows that he is not sound asleep(Malcolm 1956, 21). Others suggested that studying dreams in the laboratory may be the only way to talk senseabout dreams: Couldnt our retrospective impression of having dreamt be profoundly misleading, the product of amemory insertion produced instantaneously at the moment of awakening (Dennett 1976)? If so, dream reportswould be virtually worthless for the study of dreaming. Today, most reject these radical forms of skepticism aboutdreaming and dream reporting. Yet, the exact contribution of dream reports to a science of dreaming continues tobe controversial (for my own take on this, see Windt 2013 and Dreaming, chapters 1 and 4).

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There has certainly been important methodological progress. There are well-established methods for scoring thecontent of dream reports. Also, while early dream researchers tended to identify dreaming and REM sleep, mostcontemporary researchers allow that dreams can occur in all stages of sleep. Neuroimaging paints a differentiatedpicture of how the transition from wakefulness via sleep onset and the stages of NREM sleep to REM sleep is accom-panied by regional changes in brain activation patterns. These shifts nicely match the phenomenological character-istics of dreamingdreams, for instance, are intensely visual and emotional and often include motor imagery, aswould be predicted from the high activation of the temporo-occipital, motor, and limbic areas in REM sleep (Des-seilles 2011). Perhaps, in the future, such data can be used to predict the content of individual dream reports (for avery rst step in this direction for sleep-onset experiences, see Horikawa et al. 2013). Or perhaps, these insights caneven be used to experimentally manipulate our dreams as they unfold. For instance, Voss et al. (2014; see also Voss& Hobson 2015) have investigated whether electrical stimulation over the frontal-temporal areas, which are nor-mally deactivated in REM sleep, can induce dream lucidity, or the realization that one is dreaming while one isdreaming. And nally, the contrast between dreaming and nondreaming within the same sleep stage may extend ex-isting work on the neural correlates of consciousness (Noreika 2009, Siclari 2014).

There has also been theoretical progress. Philosophers of mind now commonly accept that dreams are experiences,in the sense that dreams are phenomenal states or that it is like something to dream, and they have begun to developpositive accounts of how exactly dreams can be related to standard and altered wake states. Some, for instance,liken dreams to virtual realities, suggesting that the sense of presence and immersion targeted by modern virtual re-ality technology is at best an approximation of nocturnal dreaming (Revonsuo 1995, 2006; Metzinger 2003).Dreaming, in this view, is a multimodal hallucination that closely mimics the phenomenology of being awake. Othersargue that dreaming should rather be likened to imagining or daydreaming, or question whether dreaming involvesbeliefs (McGinn 2004; Ichikawa 2009).

All of this gives rise to important conceptual and methodological questions. Where exactly should the concept ofdreaming dreaming be located on the map of concepts commonly used to describe standard and altered wakestates? What is the relationship between dreaming and dream reporting, and how do dream reports relate to othertypes of evidence commonly used for the study of dreaming? And what role does phenomenal selfhood, or the ex-perience of being or having a self, play in different types of dreams?

In Dreaming, I integrate results from scientic sleep and dream research with theoretical-conceptual considerationsfrom philosophy of mind and cognitive science to work towards a new, comprehensive framework for describingdreaming. I also consider changing theoretical conceptions of sleep and dreaming throughout the history of philos-ophy up until the present and investigate how they have inuenced (or have themselves been inuenced by) empiri-cal ndings. Often, these historical bypaths raise important but forgotten questions and highlight the contingenciesof currently popular views. The next post is an introduction to a central theme discussed throughout the book. Thisis the claim that the analysis of self-experience in dreams is the key towards a more comprehensive theory of dream-ing, but can also inform contemporary theories of self-consciousness.

References

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Dennett, D. C. (1976). Are dreams experiences? Philosophical Review, 85(2), 151171.

Desseilles, M., Dang-Vu, T. T., Sterpenich, V., & Schwartz, S. (2011). Cognitive and emotional processes duringdreaming: A neuroimaging view. Consciousness and Cognition, 20(4), 9981008.

Horikawa, T., Tamaki, M., Miyawaki, Y., & Kamitani, Y. (2013). Neural decoding of visual imagery during sleep. Sci-ence, 340(6132), 639642. doi:10.1126/science.1234330.

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