Figure 1.

Improvement in performance speed across training. Improvement during training session 1 (trials 1–12) was similar for subjects trained at 10 AM (group 1, □) and 1 PM (groups 2 and 4, ⋄; and group 3, •). Subjects in group 3 performed a second successive training session (trials 13–24), demonstrating modest continued improvements, similar to the predicted improvement rate based on the logarithmic regression across the first 12 trials of training in Session 1 (broken line).