We present evidence that changeover delays (CODs) create response chunks and that the discriminative control of these units contributes to observed preference during concurrent variable-interval (VI) VI schedules of reinforcement. Two experiments were conducted with pigeons. Both utilized multiple VI 30-s VI 60-s, VI 30-s VI 60-s schedules of reinforcement. One of the VI 30-s schedules was further paired with a 2.5-s changeover delay (COD). After training, unreinforced probes trials were conducted that paired the two stimuli associated with the VI 30-s schedules. In both experiments, during training, birds showed a preference for the VI 30-s schedule over the VI 60-s schedule. This preference was more extreme for the schedule pair in which a COD was programmed with the VI 30-s schedule. Further, an analysis of molecular response patterns found that the application of a COD led to discrete bursts of rapid responding when birds first switched into the VI 30-s schedule. This burst was not observed at the VI 30-s schedule in which no COD was assigned. Finally, during probes we observed a preference for the VI 30-s stimulus associated with a COD, but only when our probes maintained discriminative control of response bursts. Without this discriminative control, preference was reversed, mirroring the local reinforcement rates obtained during training.