Free-recall benefit, inhomogeneity and between-item interference in working memory

We investigated visual working memory (VWM) with a whole-report task, where participants were asked to sequentially recall all the items in an order either chosen by themselves (free recall) or randomly chosen by the computer (forced recall). Comparisons between free and forced recalls helped us understand important but largely neglected aspects of VWM, such as inhomogeneity (different levels of precision) and between-item interference. One unique part of our task was the introduction of a separate item-selection stage before each recall, during which participants located the next item to recall. Their mouse trajectory was recorded and served as a dynamic measure of between-item interference over time. We found a free-recall benefit: the overall precision of all items is higher in free recall than in forced recall. Meanwhile, during item-selection, free recall is associated with faster localization of the target and less interference from the other items in memory. We also found evidence for inhomogeneity and discuss the connection of inhomogeneity and between-item interference to the free-recall benefit.