Differential access to memory traces in the production of mental experience.

Two experiments were performed to determine the nature of the memory traces used in the production of mental experiences (dreams, daydreams). Free associations with dreams, collected upon experimental awakenings in Sleep Onset and rapid eye movement (REM) sleep, were classified as strict episodes, abstract self-references, or semantic traces, adapting Tulving's model (Experiment 1). Results showed that associations with Sleep Onset dreams were mainly strict episodes while REM associations were evenly distributed: that represents a psychophysiological state-dependency of the access to memory traces. A comparison of free associations with dream, daydreams, and films (Experiment 2) showed a similarity between access to memory traces in daydreaming and Sleep Onset dreaming. Physiological condition was not a discriminating factor. This homogeneity suggests that cognitive processes involved in the creation of original narrative sequences may be similar in sleep and waking. These findings and their interpretation tend to support a unitary theory of the mind rather than dichotomous models which, in dream research, have often been misleading.