Changes Accompanying Practice upon Successive Samples of Verbal Material

Three groups of rats received either continuous, partial, or zero reinforcement in a first acquisition phase which was followed by an extended extinction phase. Then all Ss were given a reacquisition phase under continuous reinforcement conditions followed by a second extinction phase. While the usual partial reinforcement extinction effect (PREE) was found during the major part of the first extinction phase, it disappeared during the last few trials of that phase. No PREE was obtained during the second extinction phase in any of the three sections of the runway. The abolition of the PREE was attributed to the extinction of the r_F-s_F mechanism in the partial reinforcement group.