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The aims of the experiment were: (1) to establish the proportion of sleep stages in morning spontaneous awakening and to observe whether any stage-dependent differences can be found in the mentation reports; and (2) to compare the characteristics of mental activity during sleep onset (SO) and during the latest sleep period. One hundred forty-four dream reports and their association reports were collected from 36 subjects in a lab experimental design. Dream reports were analyzed as to structure (length, narrative continuity), content (self, setting, lab references, nonself characters, dimensional distortions, body feelings, bizarreness and emotions), and awareness (reality testing). Associations were classified as episodic, abstract self-referred, and semantic memories. The morning awakenings results were not affected by the stage of sleep during which dreaming occurs. SO reports prevalently show a lifelike nature, while sleep-offset reports are prevalently dreamlike. On the other hand, there seems to be a similar availability of mnemonic systems in the two sleep conditions.

Upon nighttime experimental awakening of 27 subjects in four sleep conditions (sleep onset early; sleep onset late; Stage 2; and rapid eye movement, REM, sleep), 108 dream reports and their association reports were collected. Dream reports were analyzed for length (temporal units) and content categories (continuity; implausibility; presence of the dreamer [i.e., "the self"], a setting, characters). Associations were classified as episodic, abstract self-referred, and semantic memories. The two sets of results tend to show a basic homogeneity among mentation reports in the four sleep conditions considered. These findings are interpreted as supporting the hypothesis that the same cognitive mechanisms operate, at different levels of engagement, in dream generation rather than the hypothesis of multiple dream-generation systems dependent upon the physiological characteristics of the various sleep stages.

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Reports of 56 dreams from 5 subjects, given upon awakening during the second REMP, were analyzed and compared with a further 3 reports of each dream, obtained the following morning, 3 days, and 1 wk. later, using a system of Coding Units (CUs) and the Scoring System for Latent Structure of Foulkes. There were no significant differences between the second, third, and fourth reports, while the most important differences between the first and subsequent reports concerned: (a) a decrease in the number of CUs, words and sentences as indicated by the scoring; (b) a partial restructuring of the material, interpretable as secondary revision; (c) a decrease in the motivational component (interactive sentences) vs the cognitive component (associative sentences); (d) a decrease in the interactive sentences with Ego present in the text vs those without Ego present. Results are discussed in the light of interference and repression hypotheses.

Nielsen's model presents a new isomorphic brain-mind viewpoint, according to which the sole dream generator is found in a REM-on (explicit or covert REM) mechanism. Such a model cannot explain the dreamlike activity during SWS (slow wave sleep), SO (sleep onset) and in the last period of sleep. Moreover the hypothesis contrasts with Solms's data, which show that dreaming is present also in case of destruction of the REM generator.[Nielsen; Solms]