To peck or not peck: Which do pigeons prefer?

Animals are expected to minimize time and effort to reinforcement. Thus, not pecking should be preferred over pecking. However, even if time is held constant, pigeons often peck when it is allowed but not required (e.g., fixed time schedules), but with such schedules pecking may be adventitiously reinforced. In the present experiment, to better compare a schedule of reinforcement that requires pecking with one that requires the absence of pecking, we compared a modified fixed-interval (FI) schedule in which reinforcement follows the first peck after the interval has elapsed and a differential-reinforcement-of-other behavior (DRO) schedule, which requires pigeons to abstain from pecking for a similar interval. The delay to reinforcement was matched on a trial-by-trial basis by yoking the duration of the FI to match the DRO schedule that preceded it. Of 12 pigeons, six preferred the DRO schedule over the FI schedule and six did not show a schedule preference. Those that were indifferent between the schedules apparently had a stronger spatial preference than their schedule preference. Individual differences in the preference of the pigeons may have been related to their behavior during the DRO schedule.