Serial dependence in time perception requires consistent motor responses, not shared memory alone

Serial dependence-the bias from recent experience on present response-has been attributed to shared memory representations, yet previous studies yielded contradictory findings about whether consistent motor responses are required. To address this debate in time perception, we tested whether serial dependence emerges when tasks share identical stimulus features but differ only in response modes. We interleaved temporal reproduction and bisection tasks using a post-cue design that held duration encoding constant while varying motor output across trials. Grounded in binding and retrieval in action control (BRAC) theory, we hypothesized that response-feature binding retrieval drives serial dependence. Using structural equation modelling (SEM), we dissociated perceptual (stimulus-driven) and decisional (response-driven) components. With the same task, we replicated repulsive perceptual serial dependence and attractive decisional carryover. Critically, both effects vanished across tasks despite identical stimulus processing-demonstrating that response-mode consistency, not shared memory alone, drives sequential biases in temporal judgements. Our SEM approach uncovered repulsive perceptual influences that standard regression missed, highlighting its power to isolate overlapping effects. These findings reveal that response-specific reactivation of event files underpins serial dependence in temporal decision-making.