Auditory and visual working memory loads reduce fixation spread during free scene-viewing

Retaining information in working memory (WM) interferes with eye movements. Specifically, the presence of visual (color patches) and verbal (alphabet letters) WM loads reduced fixation spread during the free viewing of scenes (Cronin et al., 2020). In the present study, we examined whether auditorily or visually presented verbal WM loads similarly interfere with the free viewing of scenes. If the visual components of WM are critical to the reduction of fixation spread, no such reduction would occur with auditorily presented WM load. A sequence of seven letters was presented visually in the center of the monitor (Experiment 1, N=48) or auditorily through headphones (Experiment 2, N=48) as memory items, followed by a scene image during which eye movements were recorded. Under the load condition, participants maintained the letter sequence during scene-viewing and were tested by a memory probe at the end of each trial. In contrast, under the no-load condition, participants merely viewed the scene without any probe. The results of Experiment 1 indicated that the scan path length and the dispersion of fixations from the center under the load condition were smaller than those under the no-load condition. The same pattern of results was found when the memory items were presented auditorily in Experiment 2. These findings demonstrate that verbal WM load reduced fixation spread during the free viewing of scenes, regardless of the presentation modality. The reduction of fixation spread found in Cronin et al. (2020) was not specific to the presence of the visual component in the memory material. Rather, the present results suggest that modality-independent WM load restricts eye movement control, resulting in the shrinkage of the fixation spread.