Processing of a Subliminal Rebus during Sleep: Idiosyncratic Primary versus Secondary Process Associations upon Awakening from REM- versus Non-REM-Sleep.
Frontiers in Psychology January 1, 2017 Jana Steinig, Ariane Bazan, Svenja Happe et al.
The study tested whether REM-sleep involves primary process thinking (associative, condensational) and non-REM-sleep involves secondary process thinking (perspective-taking, logical). Participants were subliminally shown a rebus image combining a comb and a raft, which together form the German word for "without a struggle." After awakenings from REM and non-REM sleep, they gave dream reports and free associations. Using objective association norms, conceptual associations related to the individual images (indicating secondary process) were significantly more frequent after non-REM awakenings than REM awakenings.