Abstract
The ability to guide attention is suggested to be superior for one of multiple items in working memory (WM). While this ability has been traditionally attributed to internal attention (Olivers et al., 2011), a new study proposed that the item with higher memory precision guides external attention (Williams et al., 2019). However, because internal attention also boosts precision, previous studies were unable to dissociate these two theories. Here, we aimed to independently manipulate internal attention and precision on the same trial. On each trial, two colors were shown. Then, on 70% of the trials, memory for each color was sequentially tested using a three-alternative forced-choice task. On 30% of the trials, a search task was given to quantify attentional guidance. Before either of these tasks, a retro-cue indicated which color will be tested first, thus should be attended. Critically, participants were also instructed that the test for the second color will require higher precision, as it will involve lure colors more similar to the memory color, making them harder to distinguish. Thus, we encouraged participants to direct their internal attention to the cued color while storing the non-cued color with higher precision via instructions (Experiment 1), additional feedback (Experiment 2), and reward (Experiment 3). Experiment 4 reversed the order of the test on some trials to control for the effects of output interference. To unconfound task difficulty from assessing precision, a minority of trials in each experiment tested both items with equal lure-target similarity. In all experiments, the cued item was reported more accurately, implying its higher precision. These results indicate that dissociating internal attention and precision in WM may not be possible, revealing the difficulty of isolating the determining factor of attentional guidance as internal attention or precision.