Several theories claim that dreaming is a random by-product of REM sleep physiology and that it does not serve any natural function. Phenomenal dream content, however, is not as disorganized as such views imply. The form and content of dreams is not random but organized and selective: during dreaming, the brain constructs a complex model of the world in which certain types of elements, when compared to waking life, are underrepresented whereas others are over represented. Furthermore, dream content is consistently (...) and powerfully modulated by certain types of waking experiences. On the basis of this evidence, I put forward the hypothesis that the biological function of dreaming is to simulate threatening events, and to rehearse threat perception and threat avoidance. To evaluate this hypothesis, we need to consider the original evolutionary context of dreaming and the possible traces it has left in the dream content of the present human population. In the ancestral environment human life was short and full of threats. Any behavioral advantage in dealing with highly dangerous events would have increased the probability of reproductive success. A dream-production mechanism that tends to select threatening waking events and simulate them over and over again in various combinations would have been valuable for the development and maintenance of threat-avoidance skills. Empirical evidence from normative dream content, children's dreams, recurrent dreams, nightmares, post traumatic dreams, and the dreams of hunter-gatherers indicates that our dream-production mechanisms are in fact specialized in the simulation of threatening events, and thus provides support to the threat simulation hypothesis of the function of dreaming. Key Words: dream content; dream function; evolution of consciousness; evolutionary psychology; fear; implicit learning; nightmares; rehearsal; REM; sleep; threat perception. (shrink)

Although philosophical approaches to the self are diverse, several of them are relevant to cognitive science. First, the notion of a 'minimal self', a self devoid of temporal extension, is clarified by distinguishing between a sense of agency and a sense of ownership for action. To the extent that these senses are subject to failure in pathologies like schizophrenia, a neuropsychological model of schizophrenia may help to clarify the nature of the minimal self and its neurological underpinnings. Second, there is (...) good evidence to suggest that although certain aspects of the minimal self are primitive and embodied, other aspects may be accessed only in reflective consciousness. Employing a modified concept of the minimal self, it may be possible to construct a robotic form of non-conscious self-reference that depends on an interaction between the robotic body and its environment. In contrast to the minimal self, the narrative self involves continuity over time and is directly relevant to discussions of memory and personal identity. There is growing consensus among philosophers and cognitive scientists about the importance of narrative and its relation to episodic memory and left-hemisphere functions. There are, however, at least two different views of how the narrative self is structured. On one model it is nothing more than an abstract point. On a more extended view, proposed here, the self is a rich amalgam of narratives that allows for the equivocations, contradictions, and self-deceptions of personal life. Even in this case, however, neurocognitive models contribute to our understanding of how narrative identity is structured. (shrink)

The "Nightcap," a relatively nonintrusive and "user-friendly" sleep monitoring system, was used by 11 subjects on 10 consecutive nights in their homes. Eighty-eight sleep mentation reports were obtained after spontaneous awakenings from Nightcap-identified REM sleep and 61 were obtained from NREM awakenings. Sleep mentation was recalled in 83% of REM reports and 54% of NREM reports. The median length of REM reports was 148 words compared to 21 words for NREM reports. Twenty-four percent of the REM reports were over 500 (...) words long; no NREM reports over 500 words were obtained. REM report lengths were lowest during the first 15 min of the REM cycle and longest 15–45 min into the period. In contrast, 7 of the 9 NREM reports more than 100 words long occurred within the first 15 min of NREM periods. The Nightcap thus appears to be an effective and efficient method of collecting large numbers of sleep mentation reports with correlated sleep staging under normal ecological conditions. (shrink)

In chapter 1 of Reason, Truth, and History, Hilary Putnam argues from some plausible assumptions about the nature of reference to the conclusion that it is not possible that all sentient creatures are brains in a vat. If this argument is successful, it seemingly refutes an updated form of Cartesian skepticism concerning knowledge of physical objects. In this paper, I will state what I take to be the most promising interpretation of Putnam's argument. My reconstructed argument differs from an argument (...) strongly suggested by Putnam's text. I will show that the latter argument obviously does not work. The more promising argument which I reconstruct on behalf of Putnam raises some interesting questions about the relation between the contents of one's beliefs and one's environment and about how this relation affects the evaluation of anti-skeptical arguments. I conclude that my reconstructed argument ultimately fails as a response to Cartesian skepticism: the argument engenders a skepticism about knowledge of meaning, or propositional content, which undercuts its anti-skeptical force. (shrink)

In this paper, I discuss the relationship between bodily experiences in dreams and the sleeping, physical body. I question the popular view that dreaming is a naturally and frequently occurring real-world example of cranial envatment. This view states that dreams are functionally disembodied states: in a majority of dreams, phenomenal experience, including the phenomenology of embodied selfhood, unfolds completely independently of external and peripheral stimuli and outward movement. I advance an alternative and more empirically plausible view of dreams as weakly (...) phenomenally-functionally embodied states. The view predicts that bodily experiences in dreams can be placed on a continuum with bodily illusions in wakefulness. It also acknowledges that there is a high degree of variation across dreams and different sleep stages in the degree of causal coupling between dream imagery, sensory input, and outward motor activity. Furthermore, I use the example of movement sensations in dreams and their relation to outward muscular activity to develop a predictive processing account. I propose that movement sensations in dreams are associated with a basic and developmentally early kind of bodily self-sampling. This account, which affords a central role to active inference, can then be broadened to explain other aspects of self- and world-simulation in dreams. Dreams are world-simulations centered on the self, and important aspects of both self- and world-simulation in dreams are closely linked to bodily self-sampling, including muscular activity, illusory own-body perception, and vestibular orienting in sleep. This is consistent with cognitive accounts of dream generation, in which long-term beliefs and expectations, as well as waking concerns and memories play an important role. What I add to this picture is an emphasis on the real-body basis of dream imagery. This offers a novel perspective on the formation of dream imagery and suggests new lines of research. (shrink)

Hallucinatory states are experienced not only in connection with drugs and psychopathologies but occur naturally and spontaneously across the human circadian cycle: Our nightly dreams bring multimodal experiences in the absence of adequate external stimuli. The current study proposes a new, tighter measure of these hallucinatory states: Sleep onset, REM sleep, and non-REM sleep are shown to differ with regard to motor imagery indicating interactions with a rich imaginative world, and cognitive agency that could enable sleepers to recognize their hallucinatory (...) state. Mentation reports from the different states were analysed quantitatively with regard to two grammatical–semantic constructs, motor agency and cognitive agency. The present results support earlier physiological and psychological evidence in revealing a decline in cognitive functions and an increase in simulated interactions with a hallucinatory world, en route to normal REM sleep. This leads us to introduce the hypothesis that REM sleep, which exhibits remarkably high levels of sensorimotor processes, may have evolved to serve as a virtual laboratory for the development and rehearsal of embodied cognition. The new measure of hallucinatory states presented here may also hold implications for the study of executive functions and cognitions, which might be interesting, for example, for the investigation of lucid dreaming. (shrink)

Hypnagogic and hypnopompic experiences (HHEs) accompanying sleep paralysis (SP) are often cited as sources of accounts of supernatural nocturnal assaults and paranormal experiences. Descriptions of such experiences are remarkably consistent across time and cultures and consistent also with known mechanisms of REM states. A three-factor structural model of HHEs based on their relations both to cultural narratives and REM neurophysiology is developed and tested with several large samples. One factor, labeled Intruder, consisting of sensed presence, fear, and auditory and visual (...) hallucinations, is conjectured to originate in a hypervigilant state initiated in the midbrain. Another factor, Incubus, comprising pressure on the chest, breathing difficulties, and pain, is attributed to effects of hyperpolarization of motoneurons on perceptions of respiration. These two factors have in common an implied alien ''other'' consistent with occult narratives identified in numerous contemporary and historical cultures. A third factor, labeled Unusual Bodily Experiences, consisting of floating/flying sensations, out-of-body experiences, and feelings of bliss, is related to physically impossible experiences generated by conflicts of endogenous and exogenous activation related to body position, orientation, and movement. Implications of this last factor for understanding of orientational primacy in self-consciousness are considered. Central features of the model developed here are consistent with recent work on hallucinations associated with hypnosis and schizophrenia. (shrink)

Felt presence, a sensation that “someone is there”, is an integral part of our everyday experience. It can manifest itself in a variety of forms ranging from most subtle fleeting impressions to intense hallucinations of demonic assault or visions of the divine. Felt presence phenomenon outside of the context of neurological disorders is largely neglected and not well understood by contemporary science. This paper focuses on the experiential and expressive qualities of the phenomenon and attempts to bring forth the complexity (...) and the richness of possibilities for inter- and intrasubjective awareness represented by these experiences. Are these simply misperceptions and hallucinations heightened and enforced by the mystical or superstitious mind? Or are these entities projections of our own “selves”, elements of self-estrangement? How are such experiences shaping our understanding of ourselves and of others? And finally, what is the interplay between intersubjective, private experiences and private or public spaces of dwelling? (shrink)