FIGURE 1.

(A) Experimental design and time line of Experiments 1 and 2. In the Learning phase participants learned a short (40) or a long list (Experiment 1: 160, Experiment 2: 320) of word-pairs (within-subject cross-over design). During the following night, they were allowed to sleep at home (sleep group – blue fills) or stayed awake while watching animal documentaries at the lab (wake group – green fills). Roughly 36 h after the Learning phase, retrieval of the word-pairs was tested (Retrieval phase, see further explanations in the Section “Materials and Methods”). (B) Mean (SEM) absolute number of word-pairs correctly recalled immediately after learning (Learning phase) and at retrieval testing 36 h later (Retrieval phase) in Experiments 1 and 2 (Note that scaling of the y-axis was adapted between the experiments). (C) Mean differences (SEM) between performance at delayed recall during the Retrieval phase minus performance at immediate recall during the Learning phase (used as measure of retention) in Experiments 1 and 2. (D) Individual data for each participant’s performance during the Retrieval phase (word pairs recalled at delayed recall – y-axis) plotted against his performance during the Learning phase (word-pairs recalled at immediate recall – x-axis) for each condition in the sleep (blue) and the wake (green) groups (Note that scaling of the axes was adapted between the conditions). ^∗∗p ≤ 0.01, ^∗p ≤ 0.05.