视觉工作记忆的同类别存储优势

概念规律如记忆项间的类别关系如何影响视觉工作记忆容量是一个有争议的问题。针对该问题, 学界存在两种预测截然不同的假说：(1)混合类别优势假说, (2)同类别优势假说。综述文献发现, 该类研究均采用带有细节特征的真实客体作为实验材料, 因此前人研究中发现的混合类别优势效应或同类别优势效应中必然混有低水平知觉特征的影响。故本研究采用去除细节信息的动物剪影作为记忆材料来排除上述因素的影响, 旨在厘清上述两种假设, 并采用对侧延迟活动作为神经指标, 来进一步探讨概念规律影响工作记忆容量的内在机制。两个行为实验发现, 不论记忆项同时呈现还是序列呈现, 均存在同类别记忆优势效应。脑电实验结果发现相比记忆不同类别客体, 记忆同等数量的同类别客体诱发的对侧延迟活动的幅值更小。上述结果一致表明, 视觉工作记忆可借助概念的方式将同类别客体加以组织, 从而有效扩大视觉工作记忆容量, 支持了同类别优势假说。

Same-category advantage on the capacity of visual working memory

Visual working memory (VWM) is a limited-capacity cognitive system that is responsible for temporarily storing up to three or four items, maintaining their availability for current cognitive processing. Although VWM capacity is limited, the limit is not fixed. Factors such as the complexity, statistical regularity, real-world spatial regularity, and perceptual grouping principles of memory objects can modulate this capacity. However, the potential influence of higher-order conceptual regularities, such as categorical relationships among memory objects, remains an open and controversial issue. The effect of object category on VWM capacity, if any, has two possibilities: a mixed-category advantage and a same-category advantage. The first is consistent with the neural resource theory, by which the ability to simultaneously process multiple items is limited by the extent to which those items are represented by nonoverlapping neural representations. The same-category advantage is consistent with a prediction yielded by an ideal-observer analysis of VWM, based on the rate-distortion theory. Although the mixed-category advantage is predicted by the neural resource theory, almost all current supporting evidence solely involves faces. On the other hand, although the same-category advantage is consistent with the ideal-observer prediction, there is still lack of direct evidence to support the generalization of this prediction from low-level to high-level features. Hence, in the present study, we used behavioral and electrophysiological methods to explore this issue.Here, we report two behavioral experiments and one event-related-potentials (ERPs) experiment that assess whether category knowledge affects VWM capacity. The experiments were carried out on 60 undergraduate students.A 2 (memory load: two or four) × 2 (category: same or different) × 2 (posture: high similar or low similar) within-subject design was used in Experiment 1. The results showed that category knowledge modulates the capacity of the VWM and leads to a same-category advantage.In Experiment 2, we changed the presentation of MIs from simultaneous to successive and replicated the findings from Experiment 1, demonstrating that category knowledge leads to larger memory capacity in the same-category rather than in the different-category condition, even if the MIs are sequentially presented.In Experiment 3, in addition to Cowan’s K, the contralateral delay activity (CDA, an electrophysiological index of VWM capacity) was measured to further explore the processing mechanism underlying the same-category advantage. The CDA results show for the first time that same-category objects can induce a smaller contralateral delay activity (an index of VWM capacity) than different-category objects. The CDA results combined with behavioral results indicated that category knowledge can help compact the representations of same-category objects and therefore enlarge the total information capacity of VWM.In conclusion, our data clearly demonstrate an advantageous same-category effect on the capacity of VWM, which indicates that categorical relationships among objects play an important role in expanding the capacity of VWM by enabling the grouping of same-category objects. This suggests that VWM capacity is not fixed but can be flexible depending on the type of information to be remembered. Moreover, our data also suggest that the ideal-observer prediction can be extended from low-level to high-level features.