Fig 3. Curves I through IV: Representative cumulative records based on Equation 2, and elaborated from median best-fitting parameter values (see horizontal marks in Figure 2).

Roman numerals at the end point of each record indicate pretraining condition: (I) Brief PA; (II) Extended PA and no instrumental training; (III) Extended PA and instrumental training; (IV) Extended PA, prior NA, and instrumental training. Curve V: Representative cumulative record elaborated in the same way as Curves I through IV, but based on parameter estimates that provided the best fit to Williams & Williams's (1969, Figure 1) NA data; the continuous curve stops at the median cumulative exposure to key light (44 min), and is extrapolated as a dashed curve for comparison purposes.