Effects of reinforcement duration and ratio size on discrete-trials FR responding

Two pigeons were given discrete-trials fixed-ratio (FR) training with 2-, 4-, and 8-sec hopper times and ratio sizes of 30 or 60 responses. A final phase consisted of free-responding FR 60. The following results were found: (1) Start speeds and ratio rates were an increasing function of reinforcement duration when the schedule was discrete-trials FR 60, but not when it was FR 30; (2) the FR 60 schedule resulted in a lower level of responding than did the FR 30 schedule; and (3) the positive relationship between performance and reinforcement duration with discrete-trials FR 60 did not persist with free-responding FR 60. These results suggest that discrete-trials procedures may be more sensitive to reinforcement density manipulations than free-responding procedures.