In a concurrent‐chain procedure, pigeons choose between 2 initial‐link stimuli; one is followed by terminal link stimuli that signal reliably whether food will be delivered after a delay; the other is followed by terminal link stimuli that do not signal whether food will be delivered after the delay. Pigeons prefer the former alternative even when it yields a lower overall probability of food. Recently, we proposed the Delta‐Sigma (∆‐∑) hypothesis to explain the effect: Preference depends on the difference (∆) between the reinforcement probabilities associated with the terminal link stimuli, and the overall probability of reinforcement (∑) associated with the alternative. The hypothesis predicts that, for constant ∑, animals should prefer alternatives with greater ∆ values regardless of the specific probabilities of reinforcement that determine ∆. In 2 experiments, we tested this prediction by comparing a ∆ = .5 against a ∆ = 0 alternative, with the former obtained with different pairs of reinforcement probabilities across conditions. The results supported the hypothesis when the 2 probabilities defining ∆ were significantly greater than 0, but not when one of them was close to 0. The results challenge our theoretical accounts of suboptimal choice and the variables considered to determine pigeons’ preference.

中文翻译：

---

在次优选择任务中检验 Δ-∑ 假设：具有不同强化概率的相同 delta

在并发链过程中，鸽子在 2 个初始链接刺激之间进行选择；一个是终端链接刺激，它可靠地发出信号是否会在延迟后交付食物；另一个紧随其后的是终端链接刺激，它不表示延迟后是否会提供食物。鸽子更喜欢前一种选择，即使它产生的食物总体概率较低。最近，我们提出了 Delta-Sigma (Δ-∑) 假设来解释这种效应：偏好取决于与终端链接刺激相关的强化概率之间的差异 (Δ)，与与终端链接刺激相关的整体强化概率 (∑)选择。该假设预测，对于常数 ∑，动物应该更喜欢具有更大 Δ 值的替代方案，而不管决定 Δ 的强化的具体概率如何。在 2 个实验中，我们通过将 Δ = .5 与 Δ = 0 替代方案进行比较来测试该预测，前者通过不同条件下的不同强化概率对获得。当定义 ∆ 的 2 个概率显着大于 0 时，结果支持了假设，但当其中一个概率接近 0 时则不支持。结果挑战了我们对次优选择的理论解释和考虑确定鸽子偏好的变量。