Manual tracking modulates representational momentum independently of visual feedback

Representational momentum (RM) refers to the forward displacement of a moving object's remembered position in the direction of motion. Although RM in continuous motion is known to depend on oculomotor tracking, it remains unclear whether manual visuomotor tracking also modulates this bias and, if so, whether the effect reflects tracking-related predictive processing or compensation for proprioceptive uncertainty. In Experiment 1, participants (N = 21) observed a horizontally moving target through a semi-transparent mirror that spatially aligned the target with the tracking hand, without providing visual feedback of finger position. Eye behavior (smooth pursuit vs. fixation) and manual behavior (manual tracking vs. stationary) were independently manipulated in a 2 × 2 within-subject design. For the perceptual (memory-based) measure, RM was smallest during fixation and increased when either smooth pursuit or manual tracking was engaged, with the largest displacement observed in the eye-and-manual tracking condition. In contrast, the kinematic measures showed an effector-specific pattern: ocular overshoot increased with concurrent manual tracking, whereas manual overshoot increased when pursuit was withheld. In Experiment 2, online visual feedback of finger position was introduced during manual tracking. Despite improving tracking quality, visual feedback did not alter RM magnitude or overshoot, and Bayesian analyses provided weak-to-moderate evidence for the null. These findings suggest that RM under continuous tracking is more closely associated with tracking-related visuomotor processing than with compensatory extrapolation driven by effector uncertainty, a pattern consistent with-though not uniquely diagnostic of-an action-oriented predictive state estimation account.