Running after two hares in visual working memory: Exploring retrospective attention to multiple items using simulation, behavioral outcomes, and eye tracking

Multi-item retro-cueing effects refer to better working memory performance for multiple items when they are cued after their offset compared to a neutral condition in which all items are cued. However, several studies have reported boundary conditions, and findings have also sometimes failed to replicate. We hypothesized that a strategy to focus on only one of the cued items could possibly yield these inconsistent patterns. In Study 1, a Monte Carlo simulation showed that randomly selecting one of the cued items as the focus in each trial increased the chance of obtaining significant “multi-item retro-cueing effects” on the mean accuracy over the trials, providing an incorrect conclusion if interpreted as evidence for attending all the cued items. These high rates to obtain such data fit with inconsistent patterns in the literature. To try and circumvent this situation, we conducted two new experiments (Studies 2A and 2B) where participants were explicitly instructed to fixate their gaze on all the cued positions, verified through eye tracking (Study 2B). These produced robust multi-item retro-cueing effects regardless of previously identified boundary conditions. Notably, gazes were clearly fixated to multiple cued positions within each trial. Nevertheless, simulation revealed that our accuracy patterns could also in principle be produced by single-item enhancement on each trial. The present study forms the first step to disentangle overt gaze-based allocation of attention from single-item focusing strategies while also highlighting the need for improved methodologies to probe genuine multiplicity in working memory.