Experiments with two stimuli (S1 and S2) and two responses suggest the existence of a stage of processing that cannot be shared between two concurrent tasks. Widespread support has been found for the hypothesis that response selection for Task2 is postponed when the S1 to S2 stimulus onset asynchrony (SOA) is short (Pashler, 1994a). At short SOAs, manipulations which impact Task2 processing prior to response selection (e.g., degradation of stimulus quality) have little effect on Task2 response times (RTs). On the other hand, manipulations which are thought to impact response selection or execution (e.g., Stroop interference) always impact Task2 RTs. There is, however, one particularly compelling demonstration that appears to be inconsistent with the response selection bottleneck hypothesis: Karlin and Kestenbaum (1968) report that the RT difference between detection (i.e., 1-choice) and 2-choice discrimination dramatically decreases with decreasing SOA. Given that the primary difference between detection and discrimination is believed to be at response selection, their result may indicate a processing bottleneck at response execution (Keele, 1973). We fail to replicate the Karlin and Kestenbaum result in two substantive replications of Karlin and Kestenbaum's tasks and procedures. In the single experiment in which Karlin and Kestenbaum's result is replicated, a simple response execution bottleneck account is ruled out by the stability of the difference between 2-choice and 3-choice discrimination times across SOA. Two additional experiments demonstrate that response preparation and task strategy do not substantially contribute to the attenuation of response selection-level effects with decreasing SOA.

中文翻译：

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双任务干扰中的决策与响应

两个刺激（S1 和 S2）和两个响应的实验表明存在一个不能在两个并发任务之间共享的处理阶段。当 S1 到 S2 刺激开始异步 (SOA) 较短时，Task2 的响应选择被推迟的假设得到了广泛支持（Pashler，1994a）。在短 SOA 中，在响应选择之前影响 Task2 处理的操作（例如，刺激质量的降低）对 Task2 响应时间 (RT) 几乎没有影响。另一方面，被认为会影响响应选择或执行的操作（例如，Stroop 干扰）总是会影响 Task2 RT。然而，有一个特别引人注目的证明似乎与响应选择瓶颈假设不一致：Karlin 和 Kestenbaum (1968) 报告说，随着 SOA 的降低，检测（即 1 项选择）和 2 项选择区分之间的 RT 差异显着降低。鉴于检测和辨别之间的主要区别被认为是响应选择，它们的结果可能表明响应执行时的处理瓶颈（Keele，1973）。我们未能复制 Karlin 和 Kestenbaum 的结果，导致 Karlin 和 Kestenbaum 的任务和程序的两次实质性复制。在复制 Karlin 和 Kestenbaum 的结果的单个实验中，SOA 中 2 选项和 3 选项区分时间之间差异的稳定性排除了简单的响应执行瓶颈帐户。