Reply to Pellón and Killeen's (2015) commentary on Boakes, Patterson, Kendig, and Harris (2015).

This reply notes the importance of data from variable-time schedules for resolving the issue of whether competition from magazine approach behavior is a major factor responsible for the concentration of schedule-induced drinking early in interpellet intervals. Pellón and Killeen propose that this temporal distribution of schedule-induced drinking reflects the effectiveness of adventitious reinforcement of this behavior over a delay, as detailed in their model. However, there is no evidence to support either of their key assumptions: (a) that schedule-induced behaviors are maintained by adventitious reinforcement ("are operants") and (b) that behaviors vary in their sensitivity to a delay before the subsequent occurrence of a reinforcer.