17 rats were trained on a FI-1 schedule for 3 days. Performance was assessed by the ratio of responses made during the 1st 30 sec. of the interval to the number made during the entire interval. Ss in 2 groups, matched on the basis of the ratio they achieved on the last day of training, were tested again either 24 hr. or 24 days later. On the test day the ratio was greater for Ss tested after the longer retention interval, indicating that forgetting in animals may be manifested as an increase in response strength if what was learned originally involved the suppression of a response. (PsycINFO Database Record (c) 2006 APA, all rights reserved)