Mazur J E
J Exp Anal Behav. 1985 May;43(3):341-51. doi: 10.1901/jeab.1985.43-341.
Pigeons chose between two alternatives that differed in the probability of reinforcement and the delay to reinforcement. A peck on the red key always produced a delay of 5 s and then a possible reinforcer. The probability of reinforcement for responding on this key varied from .05 to 1.0 in different conditions. A response on the green key produced a delay of adjustable duration and then a possible reinforcer, with the probability of reinforcement ranging from .25 to 1.0 in different conditions. The green-key delay was increased or decreased many times per session, depending on a subject's previous choices. The purpose of these adjustments was to estimate an indifference point, or a delay that resulted in a subject's choosing each alternative about equally often. In conditions where the probability of reinforcement was five times higher on the green key, the green-key delay averaged about 12 s at the indifference point. In conditions where the probability of reinforcement was twice as high on the green key, the green-key delay at the indifference point was about 8 s with high probabilities and about 6 s with low probabilities. An analysis based on these results and those from studies on delay of reinforcement suggests that pigeons' choices are relatively insensitive to variations in the probability of reinforcement between .2 and 1.0, but quite sensitive to variations in probability between .2 and 0.
鸽子在两种强化概率和强化延迟不同的选择之间做出抉择。啄红色按键总会产生5秒的延迟，然后可能得到一次强化。在不同条件下，对该按键做出反应的强化概率从0.05到1.0不等。啄绿色按键会产生持续时间可调节的延迟，然后可能得到一次强化，在不同条件下，强化概率从0.25到1.0不等。绿色按键的延迟在每次实验过程中会多次增加或减少，这取决于实验对象之前的选择。这些调整的目的是估计一个无差异点，即导致实验对象对每种选择的选择频率大致相同的延迟时间。在绿色按键的强化概率比红色按键高五倍的条件下，无差异点处绿色按键的延迟平均约为12秒。在绿色按键的强化概率是红色按键两倍的条件下，无差异点处绿色按键的延迟在高概率时约为8秒，在低概率时约为6秒。基于这些结果以及强化延迟研究结果的分析表明，鸽子的选择对0.2到1.0之间的强化概率变化相对不敏感，但对0.2到0之间的概率变化相当敏感。
