How reinforcement context affects temporal production and categorization

The behavioral theory of timing assumes that timing is governed by a pacemaker whose pulses move organisms from one state to the next, and that the speed of the pacemaker covaries with the rate of reinforcement in the experimental context. The goal of the present experiments was to clarify just what constitutes that context. In Experiment 1, pigeons responded on signaled fixed-interval 20-sec and 40- sec schedules of food reinforcement that were presented randomly within sessions (alternating condition) or between sessions (isolated condition). In Experiment 2, pigeons categorized the duration of a short or a long set of intervals in the alternating or the isolated condition. Performance in both experiments was under strong control by the signals, with scalar timing between long and short sets, but no significant differences between the alternating and isolated conditions. The context of reinforcement that determines pacemaker period can thus be specific to a particular timing task and signal.