Pigeons typically prefer a 20% probability of signaled reinforcement over a 50% probability of unsignaled reinforcement. There is even evidence that they prefer 50% signaled reinforcement over 100% reinforcement. It has been suggested that this effect results from contrast between the expected probability of reinforcement (e.g., 50%) at the time of choice and the value of the positive signal for reinforcement (100%). Alternatively, it is primarily the value of the positive signal for reinforcement itself that determines suboptimal choice. To attempt to distinguish between these two hypotheses, in Experiment 1, we gave pigeons a choice between (a) a 50% reinforcement alternative that was followed by one of two signals for 100% reinforcement, each 25% of the time, or a signal for the absence of reinforcement 50% of the time (50% contrast) and (b) a 25% reinforcement alternative that was followed by a signal for 100% reinforcement 25% of the time, or a signal for the absence of reinforcement 75% of the time (75% contrast). In spite of the difference in contrast, the pigeons were indifferent between the two alternatives. In Experiment 2, when contrast was held constant at 50% and the value of the positive signals for reinforcement were different, we found support for choice based on the value of the positive signal for reinforcement. Thus, it appears that pigeons' choice depends primarily on the value of the outcome rather than its frequency or contrast. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

中文翻译：

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鸽子的选择主要取决于结果的信号值，而不是其频率或对比度。

鸽子通常更喜欢 20% 的有信号强化概率，而不是 50% 的无信号强化概率。甚至有证据表明，他们更喜欢 50% 的信号强化而不是 100% 的强化。有人提出，这种效果是由于选择时的预期强化概率（例如，50%）与强化的积极信号值（100%）之间的对比造成的。或者，决定次优选择的主要是强化本身的积极信号的值。为了试图区分这两个假设，在实验 1 中，我们让鸽子选择（a）一个 50% 的强化替代方案，然后是两个 100% 强化的信号之一，每个 25% 的时间，或 50% 的时间没有强化的信号（50% 的对比）和 (b) 25% 的强化替代方案，然后是 25% 的时间 100% 强化的信号，或没有强化的信号75% 的时间强化（75% 的对比）。尽管对比度有所不同，但鸽子对这两种选择无动于衷。在实验 2 中，当对比度保持在 50% 且增强的正信号值不同时，我们发现支持基于增强的正信号值进行选择。因此，鸽子的选择似乎主要取决于结果的价值，而不是其频率或对比度。（PsycInfo 数据库记录 (c) 2022 APA，保留所有权利）。