When actions speak louder than words: The Final Position Judgement Task involves action imagery rather than verbal rehearsal

When imagining actions based on verbal movement instructions, maintaining an evolving mental representation across successive instructions is important. We examined this process from a working memory perspective, asking whether maintenance of verbally instructed action imagery depends on verbal working memory or can be sustained by imagery-related processes. In an adapted Final Position Judgment Task (FPJT), participants imagined four to seven successive movements from standardized auditory instructions and then judged whether an image of a human figure matched their imagined final position, once in baseline and once while repeating a syllable aloud to prevent verbal rehearsal. This articulatory suppression reduced self-reported verbal rehearsal and action imagery quality. While articulatory suppression increased errors, performance remained above chance, suggesting that it was not reducible to verbal rehearsal. Converging with this, FPJT errors were associated with visuospatial, but not verbal, working memory, with no evidence that these associations varied by FPJT condition. Across conditions, most participants reported visually rehearsing the instructed body parts in imagery, which was beneficial for FPJT performance, whereas verbal rehearsal was associated with slow responding. Our results suggest that maintaining verbally instructed action imagery in the FPJT relies primarily on imagery-related visual rehearsal supported by visuospatial working memory, with verbal rehearsal playing a rather supportive role. Given that FPJT performance also covaried with mental body rotation and mental paper folding performance, the FPJT can serve as a behavioral measure of action imagery ability.