Hyung-Bum Park¹ (), Edward Awh¹; ¹University of Chicago

The debate on serial dependence questions its origin in perceptual versus post-perceptual working memory (WM) components, with mixed findings on whether perceptual decisions exhibit attractive serial dependence toward previous target or repulsive bias linked to sensory adaptation. The present study aims to examine the dynamics of serial biases across perception and WM processes at consolidation and retrieval. Participant performed a two-part experiment, with the first part involved immediate continuous estimations of color on color-wheel within view (perceptual report). The second part involved WM recall with dual-response. A memory color followed by masks was reported after stimulus offset (consolidation report), and the same item was reported again after delay on another color-wheel (retrieval report). Mouse trajectories for all responses were recorded to index direction and magnitude of serial bias. Behavioral reports showed a gradual evolution of serial bias across opposite directions: repulsion in perceptual reports, moderate attraction in consolidation, and stronger attraction in retrieval. Critically, we found a unique mouse trajectory pattern in consolidation reports, with a repulsive curvature from the previous target appearing on the color-wheel, while the overall trajectory exhibited attraction bias. Further examination of moment-by-moment trajectories, coupled with a median-split of movement onset latency, captured a ‘repulsion-to-attraction’ transition in consolidation reports, with early repulsion evolving into attraction as movements progressed. Moreover, the median-split analysis revealed a magnification of bias from early-onset to late-onset trials within their directions (stronger repulsion vs. attraction in perceptual and WM reports, respectively). These suggest that changes in serial biases across processes are not solely time-dependent, but originate from distinct perceptual and WM mechanisms. The repulsion-to-attraction transition during the WM consolidation phase offers an intermediate window into the interplay between sensory adaptation and serial dependence, jointly shaping serial bias in behavioral reports. Together, our study provides evidence supporting the mnemonic origin of serial dependence.