Pratte Michael S
Mississippi State University, PO Box 6161, Mississippi State, MS, 39762, USA.
Atten Percept Psychophys. 2020 Aug;82(6):2937-2949. doi: 10.3758/s13414-019-01902-5.
Visual working memory is often characterized as a discrete system, where an item is either stored in memory or it is lost completely. As this theory predicts, increasing memory load primarily affects the probability that an item is in memory. However, the precision of items successfully stored in memory also decreases with memory load. The prominent explanation for this effect is the "slots-plus-averaging" model, which proposes that an item can be stored in replicate across multiple memory slots. Here, however, precision declined with set size even in iconic memory tasks that did not require working memory storage, ruling out such storage accounts. Moreover, whereas the slots-plus-averaging model predicts that precision effects should plateau at working memory capacity limits, precision continued to decline well beyond these limits in an iconic memory task, where the number of items available at test was far greater than working memory capacity. Precision also declined in tasks that did not require study items to be encoded simultaneously, ruling out perceptual limitations as the cause of set size effects on memory precision. Taken together, these results imply that set size effects on working memory precision do not stem from working memory storage processes, such as an averaging of slots, and are not due to perceptual limitations. This rejection of the prominent slots-plus-averaging model has implications for how contemporary models of discrete capacities theories can be improved, and how they might be rejected.
视觉工作记忆通常被描述为一个离散系统，在这个系统中，一个项目要么存储在记忆中，要么完全丢失。正如该理论所预测的，增加记忆负荷主要影响项目在记忆中的概率。然而，成功存储在记忆中的项目的精度也会随着记忆负荷的增加而降低。对这种效应的主要解释是“插槽加平均”模型，该模型提出一个项目可以在多个记忆插槽中重复存储。然而，在这里，即使在不需要工作记忆存储的图像记忆任务中，精度也会随着集合大小的增加而下降，这排除了这种存储解释。此外，虽然“插槽加平均”模型预测精度效应应该在工作记忆容量极限时趋于平稳，但在一个图像记忆任务中，精度在远远超过这些极限时仍继续下降，在该任务中，测试时可用的项目数量远远大于工作记忆容量。在不需要同时对学习项目进行编码的任务中，精度也会下降，这排除了感知限制是集合大小对记忆精度产生影响的原因。综上所述，这些结果表明，集合大小对工作记忆精度的影响并非源于工作记忆存储过程，如插槽平均，也不是由于感知限制。对突出的“插槽加平均”模型的这种否定，对于当代离散容量理论模型如何改进以及如何被否定具有启示意义。
