Group 1 received 6,000 trials on CRF, Group 2 6,000 trials on FR 10, and Group 3 60,000 trials on FR 10. All Ss were then extinguished under 3 conditions: the magazine click was presented on CRF, on FR 10, or not at all. The click was a weak but effective incentive for CRF Ss and a strong incentive for FR 10 Ss. With extended training the click also became an informative stimulus for FR 10 Ss in that it reduced resistance to extinction.