School of Psychology, University of Minho, Portugal.
Department of Education and Psychology, University of Aveiro, Portugal.
J Exp Anal Behav. 2020 Sep;114(2):233-247. doi: 10.1002/jeab.621. Epub 2020 Jul 28.
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.
在并发链程序中，鸽子在两个初始链接刺激之间进行选择；其中一个链接刺激之后是终端链接刺激，这些刺激可靠地表明延迟后是否会提供食物；另一个链接刺激之后是终端链接刺激，这些刺激不表明延迟后是否会提供食物。即使前者的整体食物获得概率较低，鸽子也更喜欢前者。最近，我们提出了 Delta-Sigma（∆-∑）假说来解释这种效应：偏好取决于与终端链接刺激相关的强化概率之间的差异（∆），以及与替代方案相关的强化的整体概率（∑）。该假说预测，对于恒定的∑，无论决定∆的具体强化概率如何，动物都应该更喜欢具有更大∆值的替代方案。在 2 项实验中，我们通过比较∆=.5 与∆=0 的替代方案来检验这一预测，其中前者是通过不同条件下的不同强化概率对获得的。当定义∆的 2 个概率明显大于 0 时，结果支持该假说，但当其中一个概率接近 0 时，结果则不支持该假说。这些结果挑战了我们关于次优选择的理论解释，以及我们认为决定鸽子偏好的变量。
