In a recent study we established that following a partial acquisition of a brightness discrimination escape task (15 trials), Sprague-Dawley albino rats exhibited a long-term spontaneous improvement of performance (LTSI) after 7 to 14 days. Some evidence suggests a relation between the strength of the initial training and the delay of the optimal retention performance. This study investigates such a possibility in studying performance of rats (number of trials needed to reach a criterion of 10 errorless trials) following nine different retention intervals: 10 min, and 1, 3, 5, 7, 10, 14, 21, and 28 days, after a strengthened initial training (25 trials). Under those conditions, LTSI occurred after a delay of 5 to 7 days. Theoretical implications for an inverse relationship between the strength of initial training and the length of delay leading to LTSI are discussed. © 1990 Academic Press, Inc.
