Do dreams really guard sleep? Evidence for and against Freud's theory of the basic function of dreaming

According to the classic theory framed by Sigmund Freud, the basic and teleological function of dreaming is to protect sleep from disruption (Freud, 1900/1953); a quite rational hypothesis since sleep constitutes a vital need for living species (Kryger et al., 2011). This aspect of Freud’s dream model—which as a whole is considered as the initial cornerstone of psychoanalysis (Laplanche and Pontalis, 1988)—leads to two empirically testable conjectures, thus allowing its scientific examination: (1) arousal during sleep triggers dreaming; and (2) non-dreaming causes sleep disruption.We review here the experimental, medical, and neuropsychological data which allow testing these two conjectures; in this paper, the term “significant” denotes statistical significance at the p < 0.05 level.