Factors affecting choice of signaled or unsignaled food schedules.

Choice between signaled and unsignaled food schedules was assessed in two experiments using a shuttlebox. Experiment 1 examined preference with both a five-second signal and a thirty-second signal. Subjects preferred the unsignaled side with a five-second signal but preferred the signaled side with a thirty-second signal. Experiment 2 assessed preference using either a commitment procedure (a shuttle response resulted in exposure to the schedule for a fixed time) or a noncommitment procedure (each shuttle response changed the schedule in effect). Subjects preferred the signaled condition with the commitment procedure but the unsignaled condition with the noncommitment procedure. These results indicate that the discrepant findings of earlier studies are due to procedural differences involving signal duration and choice commitment. The data are consistent with a conditioned reinforcement interpretation of choice.