Effects of probability and duration of reinforcement on choice behavior in discrete trial intervals

Pigeons were trained to peck at blue or amber keys presented simultaneously in discrete trials. In the first experiment, there were seven discrete trials with reinforcement scheduled probabilistically every seventh trial in the reinforcement interval. The key light went off either after two seconds with no response or after a response had been made. There were no contingencies on pecking in the first six post-reinforcement trials, while on the seventh and following trials the reinforcement remained available until a response was emitted on the key with the scheduled reinforcer. The first experiment varied probability of reinforcement and held duration of reinforcement equal. In the second experiment, duration of reinforcement was the variable manipulated, with all other reinforcement variables, including probability of reinforcement presentation, held equal