Shaping, acquisition, extinction and spontaneous recovery of lever pressing behavior in pigs under feeding scheme of livestock industry

Abstract

The present study examined operant conditioning in domestic pigs that were bred under the ordinary feeding scheme of the livestock industry. Two castrated male pigs were shaped to press a lever by successive approximation method with 3.4-g food pellets and 2-s buzzers. Shaping was accomplished within about 40 min and about 90 reinforcements. During acquisition, the number of responses in a 20-min session was increased from about 100 to 200 during 20 sessions of training with continuous reinforcement. During extinction sessions, rapid extinction and minimal spontaneous recovery was observed. In later sessions during the acquisition phase, pigs began to press the lever several times consecutively before consuming rewards in the feeder. In Experiment 2, the consecutive responses were eliminated when only one reinforcer was delivered for a train of responses. This result suggests that the consecutive response is a foraging strategy to save response cost required for shuttling behavior between the lever and the feeder.