Exploring the capacity and executive function of vibrotactile working memory through the frequency sequencing task

Working memory (WM) research has primarily focused on visual and verbal information, while relatively little is known about tactile information. This study aims to explore the capacity of vibrotactile WM (vtWM) using the frequency sequencing task, and focuses on its functions in the simultaneous maintenance and transformation of information, supervision, and coordination. We conducted four experiments: Experiments 1 and 2 used the simple frequency sequencing task, while Experiments 3 and 4 added additional processing tasks (a visual processing task and a tactile processing task) to the simple frequency sequencing task. We demonstrated a 3-unit capacity during vtWM that matches Cowan's suggested 3-5 unit chunks of pure WM capacity when memory items cannot be chunked. This measured capacity remains stable across WM tasks with different frequency values. Additionally, the mean accuracies of both the frequency sequencing task and the processing task were significantly different between Experiments 3 and 4. These results provide preliminary evidence for the relative dissociation of tactile and visual executive functions in WM. Taken together, by providing a new method for investigating the capacity of vtWM, the present study expands the field of WM capacity studies to nonverbal and nonvisual modalities.