The across-trial accumulation of cardinal illusion in orientation estimation attenuates the significance of serial dependence.

The human visual system employs two complementary mechanisms-feature contrast enhancement and continuity maintenance-to effectively process extensive visual input. However, how these mechanisms interact to shape visual perception remains poorly understood. In this study, participants were asked to estimate the orientations of a serial of Gabor patches. Our results revealed two key perceptual biases: a cardinal bias, characterized by systematic deviations away from cardinal orientations (e.g., 0°), and serial dependence, where current estimates were attracted toward previously presented orientations. Notably, we found that the cumulative influence of cardinal bias across trials produced a repulsive history effect. When this effect was statistically removed from the estimation errors, the strength of serial dependence significantly increased. This suggests that while feature contrast enhancement and continuity maintenance generate opposing behavioral effects, they may share overlapping computational or neural processes. These mechanisms likely interact dynamically to refine and optimize visual perception. Moreover, our findings offer a robust methodological framework for isolating serial dependence effects, enabling future studies to more accurately quantify their role in perceptual decision-making. By disentangling these interacting biases, this work advances our understanding of how the visual system balances sensitivity to feature differences with the integration of perceptual history.