Introduction

Introduction
Although Freud (1900) proposed that dreaming and, specifically, the meaningful content of dreams are related to mental functioning, the tenuous and misunderstood nature of dreams has made the proposition of empirically providing support for, or falsifying, this claim very problematic. The inability to study the effects of dreams on mental functioning has forced many researchers to view dreams as the result of random neural activity (e.g., the activation-synthesis hypothesis; Hobson and McCarley, 1977). If postulations regarding the random nature of dreams are indeed true, then it becomes challenging to construct a theory of how the phenomenology of the dream state could serve a functional role and be better understood through an evolutionary analysis. However, recent research, to be discussed in this paper, which takes into account the physiological mechanisms underlying sleep and dreams, the content of dreams, and the environmental conditions of selection, points toward the natural selection of dreaming as a state of consciousness which has persisted across the development of the human species. This tends to suggest that the dream state was selected for as an adaptation which increases overall fitness. The leading theory addressing the adaptive qualities of dreaming uses the concept of virtual threat, defined as a dream-state wherein a threatening situation is constructed virtually, and explains that through the rehearsal of various threatening scenarios we may be better equipped to handle real-world threats (Revonsuo, 2000). While this theory offers a plausible evolutionary account of dreaming, the goal of the current paper is to extend the theoretical underpinnings of this hypothesis by commenting on other fitness-enhancing aspects of dreams and the broader influence of dreaming in the evolution of higher mental functioning.