The degree to which responding came under discriminative control by the stimuli in each condition, and hence the extent to which the stimulus-food relation was discriminated, may be inferred from the speed with which responding shifted from favoring the H→ L key to favoring the L →H key at the probability-reversal time. To illustrate, Fig. 4 shows response rates on the L →H and H→ L key as a function of time (s) since the most recent food delivery, from a selection of Continuous and Discrete conditions. The data shown in Fig. 4 were calculated from responses summed across all six pigeons. From Fig. 4, it is apparent that response rates changed in accordance with the probability reversal in both Continuous and Discrete conditions: Generally, response rates on the L →H key were lower before the reversal, and higher after the reversal, whereas responding on the H→ L key showed the opposite pattern of change.