44 RATS RECEIVED ACQUISITION TRAINING IN A RUNWAY FOR 3 TRIALS EACH DAY FOR 6 DAYS WITH 2 LEVELS OF REWARD MAGNITUDE (.09 VS. 1.08 GM. OF FOOD) AND 2 SCHEDULES OF PARTIAL REWARD (PRESENCE VS. ABSENCE OF NONREWARDED-REWARDED; N-R TRANSITIONS). ABILITY OF LARGE PARTIAL REWARD TO INCREASE RESISTANCE TO EXTINCTION, AS PREVIOUSLY FOUND UNDER IRREGULAR SCHEDULES, WAS EXCLUSIVELY ASSOCIATED WITH N-R TRANSITIONS. LARGE REWARD PRODUCED GREATER RESISTANCE TO EXTINCTION THAN SMALL REWARD IN THE SCHEDULE CONTAINING N-R TRANSITIONS, BUT NOT IN THE SCHEDULE LACKING N-R TRANSITIONS; SMALL-REWARD N-R SCHEDULE PRODUCED GREATER RESISTANCE TO EXTINCTION THAN THE LARGE-REWARD SCHEDULE LACKING N-R TRANSITIONS. (PsycINFO Database Record (c) 2006 APA, all rights reserved)