Fig. 6.

Timeline of the encoding and test sessions of WPA task and details of the encoding and test sessions. (A) Participants in group 1 (n = 26 after excluding participants who did not complete all the task sessions) reported to the laboratory in the evening and completed the encoding session of WPA and immediate testing (Test 1, presleep) at around 9 PM and prepared for sleep. They were awakened in the morning and after breakfast completed the next testing session (Test 2, postsleep) at 10:30 AM. In group 2, participants (n = 26 after excluding participants who did not complete all the task sessions) completed the WPA encoding and immediate testing session (Test 1) at around 8:30 AM. Then, participants left the laboratory to continue their day and came back to the laboratory to complete the second testing session (Test 2, presleep) at around 9 PM. The next morning, participants were awakened at 9 AM and after breakfast completed the last test (Test 3, postsleep) at 10:30 AM. (B) In the encoding session of the WPA task, 60 pairs of words with length of three to nine letters were presented vertically stacked and shown twice in random order. Each word pair was presented for 1,000 ms and followed by a fixation cross for 1,000 ms. Immediately after encoding, subjects were trained to criterion using a test in which participants were shown one word of the pair and were required to type in the associated word. Incorrect trials were repeated, and feedback was provided. The participants had to achieve 70% accuracy to finish the encoding session. The used word pairs in the encoding session were divided into three groups of 20 word pairs for the testing sessions. In each testing session, participants were shown one word of the pair and were required to type the associated word.