Figure 5.

Data from subject 15, who was restudied at a later date. Symbols and format are as in Figure 1. The subject demonstrated 345 days of spontaneous transient entrainment (days 809-1,154) during which her average drift rate was only 0.01 h/day (4.1 hours of drift over 345 days, the linear regression drift rate was 0.00 ± 0.01 h/day). She then spontaneously resumed a nonentrained pattern (days 1,168-1,245) with an average drift rate of 0.31 h/day (23.86 h of drift over 77 days, linear regression drift rate of 0.33 ± 0.06 h/day).