ACQUISITION, EXTINCTION, AND REACQUISITION OF THE EYELID RESPONSE WERE STUDIED WITH EACH OF 43 MALE NEW ZEALAND WHITE RABBITS, 12-15 WK. OLD, AS A FUNCTION OF THE INTERSTIMULUS INTERVAL (ISI). ALTHOUGH ASYMPTOTIC RESPONSE LEVELS WERE SIMILAR FROM 250 MSEC. TO 1 SEC., RATE OF ACQUISITION WAS A U SHAPED FUNCTION OF THE ISI WITH FASTEST CONDITIONING OCCURRING AT 400 MSEC. EXTINCTION AND REACQUISITION RATES WERE SIMILAR FOR ISIS FROM 400 MSEC. TO 1 SEC., BUT THE 250-MSEC GROUP EXTINGUISHED MORE SLOWLY THAN OTHERS. LATENCY DISTRIBUTIONS WERE SIMILAR FOR THE DIFFERENT ISIS WITH CENTRAL TENDENCIES APPROXIMATELY 3 OF THE WAY THROUGH THE CS-UCS INTERVAL. A MODEL OF CONDITIONING WHICH INCORPORATED THESE DATA IS PRESENTED. (PsycINFO Database Record (c) 2006 APA, all rights reserved)