中国有句谚语：人多力量大。然而在记忆研究领域，这句话是否还适用？以往研究通常使用经典的协作提取研究范式，来考察小组模式对记忆效果的影响。研究发现协作小组提取的信息总量比等量个体单独提取的信息量的无叠加之和要少，即协作提取过程会对小组提取成绩产生消极影响，这一现象被称作协作抑制。针对该现象的机制解释，大量研究者将关注点集中于“策略破坏假说”。该假说认为协作组的提取量成绩差，是因为协作组成员的提取结果对组内其他成员最初单独形成的信息组织策略产生了干扰和破坏，因此导致协作组的提取成绩低于名义组。然而近期的一些研究结果却没有证实策略破坏假说的观点。本论文的主要贡献在于，在前人理论研究的基础上，首先检验了策略破坏是否能作为协作抑制单一影响机制的问题，在此基础上，进一步逐步推进地探索并验证了可能存在于协作抑制中的其他认知机制。

本论文包括三项研究，共5 个实验。研究一首先检验策略破坏机制是否能完全解释不同实验条件下的协作抑制现象，包括一个实验：实验1 使用无关联词作为实验材料，考察在提取阶段协作组内成员持有项目的异同对协作抑制的影响。结果发现，在协作提取过程中，小组成员所持有的信息及其各自的组织策略完全不同时，协作抑制现象仍出现。因此，本研究的结果认为在策略破坏不存在时，协作抑制仍出现，即否定了策略破坏假说作为协作抑制的唯一解释。

研究二继续探索在不同提取项目协作组的实验条件下，引起或影响协作抑制的原因和因素。包括一个实验：实验2 控制了提取阶段协作组内已提取项目的反应竞争强度，以考察其对协作抑制效应的影响。结果发现，在无项目反应竞争条件下的协作组内，协作抑制现象消失。这一结果说明在不同提取项目协作组内，已提取项目的反应竞争强度是导致协作抑制的关键因素。该结果符合协作抑制的“提取抑制假说”对该现象的预测和解释。该假说的核心观点认为，协作组内成员的已提取项目对所有未提取的项目均产生了表征抑制，若小组内已提取项目的反应竞争强度越强，则对未提取项目的抑制效应就越强，因此协作抑制效应越大。

研究三通过3 个实验，将协作提取范式与情绪Stroop 范式相结合，进一步检验协作抑制的长时抑制观点。实验3 考察了协作提取后的抑制过程；实验4考察了最终个人提取任务完成后的抑制过程；实验5 考察了最终个人提取任务未完成时的抑制过程。3 个实验分别在协作提取后的不同阶段安插情绪Stroop 任务，以比较协作提取和无提取（控制）条件下的被试分别在情绪Stroop 任务中的表现，进而以反应时作为指标检验提取抑制机制的长时抑制观点。结果显示，在协作提取任务后，小组成员对情绪词颜色判断的反应时显著短于无提取条件；这种反应时的差异在未完成的最终个人提取任务中仍持续出现，然而当最终个人提取任务完成后，小组成员对情绪词颜色判断的反应时与无提取条件下的反应时无异。该结果说明，协作抑制在协作提取后随即发生，且直到最终的提取任务完全结束，抑制效应一直存在。

本论文通过三项研究，使用统一的协作提取研究范式，探索并验证了存在于协作抑制中的另一种认知机制——提取抑制机制。研究一探索了策略破坏假说是否能完全解释协作抑制现象；研究二在研究一的基础上，探索了提取抑制机制对协作抑制的影响；研究三直接验证了提取抑制机制对协作抑制发生发展的影响作用，是对研究二的补充验证。本文三项研究共同揭示了提取抑制机制在协作抑制中的作用。根据现有的研究结果，我们在文章最后讨论了协作抑制的认知模型、协作抑制研究的范式与方法以及协作抑制的个体差异研究，同时我们也分析了本文的创新性贡献并对未来研究方向做一展望。

Intuition suggests that “two heads together are better than two heads apart” when completing cognitive tasks, particularly problem solving. However, this does not appear to be the case for memory tasks. Researchers demonstrated that, during retrieval, individuals working together as a collaborative group performed much more poorly than did the same number of people recalling individually (nominal group). This phenomenon is called collaborative inhibition. The most common explanation for this effect is the retrieval-disruption hypothesis, which states that each individual’s idiosyncratic organization of overlapping information is disrupted during collaborative recall phases. However, several recent studies have obtained conflicting results concerning this viewpoint. In this dissertation, we first explored whether retrieval-disruption hypothesis could be the sole-mechanism underlying collaborative inhibition. Based on the results, we then examined another hypothesis could also contributed to collaborative inhibition besides retrieval disruption.
This dissertation includes three main studies. In the first study, which involves one experiment, item similarity was manipulated by requiring participants to study overlapping or non-overlapping materials. The unstructured instructions were then manipulated during recall tasks between conditions. The results showed that collaborative inhibition occurred for both overlapping and non-overlapping conditions in our Experiment 1.
Subsequently, response competition during collaborative recall, in addition to item similarity, was manipulated in the second study, and the results showed that when group members were instructed to monitor their partner’s recall (the response-competition condition), collaborative inhibition occurred. However, no such effect was shown when group members were instructed not to communicate with each other, but to simply recall in turn while in a group (no-response-competition condition) in our Experiment 2. Together, these results suggest that collaborative inhibition obtained in the current two studies were more likely caused by the differing instructions of each, which resulted in an inducement of response competition in collaborative settings. These results could be explained by the retrieval inhibition hypothesis.
In the third study, we investigated the inhibitory process of collaborative inhibition through three experiments by combining the collaborative memory paradigm with an emotional Stroop task. After studying emotionally negative words individually, participants completed a filler task and then were randomly allocated into three conditions. Two-thirds of participants completed a first recall task (collaborative- or individual-recall condition), while the remainder continued with the filler task (no-first-recall condition). Then, all participants completed a final individual-recall task. The emotional Stroop task, wherein participant attempted to discriminate the colours of studied words, took place at three different points across the three experiments. When performing the emotional Stroop after the first recall task (Experiment 3) or before fully completing the individual-recall task (Experiment 5), participants experienced more rapid discrimination of emotional words’ colour information in the collaborative-recall condition than in the no-first-recall condition; conversely, when the Stroop task was performed after the final individual-recall task (Experiment 4), there were no differences in discrimination among the conditions. Thus, the inhibitory process might occur immediately after collaboration and be mediated by the retrieval task. We discuss retrieval inhibition as an underlying mechanism of collaborative inhibition.
Based on the above results, we discussed the mechanisms underlying collaborative inhibition. We also discussed the methods of collaborative recall and individual researches of collaborative inhibition. In addition, we give some important points to the future studies.