An application of the active time model to multiple concurrent variable-interval schedules.

The current experiment investigates whether an active time model can account for anomalous results that have emerged from multiple schedule, concurrent variable-interval (VI) VI experiments. The model assumes that (1) during concurrent VI VI training pigeons learn a function that relates time since the most immediate response, i.e., active time, to changeover probabilities and (2) that molar preference is the result of an interaction between inter-response time frequencies and the learned active time changeover functions. Pigeons were trained under a concurrent VI 30-s VI 30-s schedule and a concurrent VI 60-s VI 60-s schedule. Probes were conducted in which VI 30-s and VI 60-s stimuli were paired. During these probes, birds allocated choices equally to the stimuli. The active time model accurately fit individual subject data. In contrast data were not fit by a variant of scalar expectancy theory proposed by Gibbon [Gibbon, J., 1995. Dynamics of time matching: arousal makes better seem worse. Psychon. Bull. Rev. 2, 208-215].