Dear Margaret,

Thank you very much for your interest in our work and for raising this issue. Concerning your first question, Exp. 2 and 3 were separate control experiments for Exp. 1, with different aspects being manipulated and we did not intend to directly compare these experiments. In Exp. 2 we aimed at showing that sleep deprivation at retrieval (also during the second night) enhances false memories. Retrieval testing took place in the morning so that the length of sleep deprivation was comparable to Exp. 1 (24 h). Exp. 3 was designed to manipulate sleep vs. wakefulness after learning without the confounding factors sleep deprivation at retrieval and circadian variation. Exp. 1 showed that the sleep group and day wake group did not differ in false memory rate. However, these two groups differed substantially with respect to circadian factors: encoding, consolidation and retrieval occurred during different circadian phases and circadian factors are known to have substantial impact on cognitive processing (e.g., Schmidt et al, 2007, Cogn Neuropsychol, 24(7), 755-789). To control for circadian variations we wanted to introduce learning and retrieval during the same circadian phase in Exp. 3 and therefore retrieval testing was shifted to 18:30. In this way, groups were not only comparable for encoding, consolidation and retrieval times but even within subjects, encoding and retrieval took place in the same circadian phase.
We further established a retention interval of 9 and 33 hours due to considerations concerning learning and retrieval times in the sleep groups. We wanted learning to take place immediately before sleep, subjects should sleep for 8 hours and retrieval testing should be done half an hour after awakening. In Exp. 3 retrieval testing was postponed to the evening phase as mentioned above, resulting in a 44 hours retention interval.

I hope this helped clarifying the issue.

All the best,

Susanne