Differential control of operant and consummatory licking in rats.

The failure of rats to optimize their behavior when drinking from two retractable spouts available for single licks was analyzed. The rats were trained in an apparatus where the contacted spout was withdrawn after completion of a lick and the other spout was presented. After 5 days of such forced spout alternation training the animals continued to emit 2.7 instead of the optimum 1.0 lick per spout presentation (LPSP). With water available in one spout only the average LPSP at the empty spout dropped to 1.2 and increased to 3.6 at the water containing spout. It is argued that the operant licks at the dry spout approach the ideal value of 1.0 LPSP whereas the number of LPSPs at the water spout is increased by the consummatory nature of licking triggered by the presence of water in the oral cavity.