24 hours after 16 white rats (2½ months old) had been conditioned for 15 trials to run on an elevated runway from starting box to food box, and the response had been extinguished to the point that the latent period (the time elapsing after the door was opened until the rat left the starting box) had increased to 3 minutes or more, a reconditioning curve for this response was determined. Reconditioning was carried on until 3 successive responses were made with latent periods of 5 seconds or less. The animals were then divided into 4 groups of 4 each and reconditioning experiments carried out in the 4 groups respectively after periods of 3, 7, 14, and 28 days. The curves showing amount of retention as a function of days after original conditioning exhibit progressive loss in retention at a rate which is initially more rapid, then more retarded. (PsycINFO Database Record (c) 2006 APA, all rights reserved)