Four pigeons were trained on a concurrent chain schedule, in the terminal links of which food was delivered according to variable interval schedules. For one key in Experiment 2 reinforcement was contingent on not responding. Three control experiments were also run: baseline, return to baseline, and unequal reinforcement frequencies. Although rate differences of over 50 to 1 were obtained in the terminal links of Experiment 2, the pigeons remained indifferent between these schedules. The only change in preference occurred in Experiment 4, where preference matched reinforcement frequency.