Memory sources associated with REM and NREM dream reports throughout the night: a new look at the data.

The data from three previously published studies on the memory sources of dreams, representing nine different moments of awakening throughout the night, are re-examined. In the original studies, elicited reports were recorded and segmented online into thematic units. The segmented reports were played back to Ss who were asked to identify memory sources or to associate to each segment. Memory sources were classified as episodic, semantic, or abstract self-references. In the meta-analysis and re-analyses reported here, the mean percentages of episodic memory sources are plotted separately for NREM and REM awakenings throughout the night. Within stages, neither NREM nor REM mean percentages differ significantly from each other, whereas between stages the mean percentage of episodic memory sources is significantly greater for NREM than for REM. Even when the correlation between report length and sleep stage is controlled by computing memory source density, the stage effect throughout the night persists for episodic memory sources. The relatively flat episodic memory curves for both NREM and REM indicate a rather constant recruitment of episodic memory sources throughout the night. No stage effect was found for strictly semantic memory sources. When semantic memory was defined generically, however, to include all non-spatio-temporal, "unmarked," information of self as well as of world, significantly more generic semantic memory sources derived from REM than from NREM reports, though not when corrected for the length of dream reports.

How are dreams made? Towards a computational model.

In order to account for how dreams are made, both information structures and energy systems must be made more explicit. This paper attempts to spell out in more detail two of the three components that Foulkes postulated as essential to dream construction, namely, memory and planning. It draws on the mechanisms in Mueller's computational model of human daydreaming, in particular, a planner--which consists of personal goals, daydreaming goals, and planning and inference rules for a particular domain--and a set of emotions that determine the choice of daydreaming goals. We analyzed the laboratory REM dream of an adult male subject in terms of the three kinds of goals in Mueller's model: namely, the personal goals that derive form the day residue elicited from the subject prior to the dream; the dream goals of reversal, rehearsal, rationalization, and revenge; and the planning goals or script identified in a metaphoric problem space. The sequence of scenes from the script determines the skeletal structure of the dream, and the emotion of humiliation, decomposed into embarrassment and anger, largely determines the choice of dream goals. Much of the dream content itself is the instantiation of an inference rule for restoring social esteem. Finally, it is argued that the kind and quantity of mechanisms that are postulated by Mueller for human daydreaming are also necessary to account for basic processes of night dream construction.