Decisional processes balance sensitivity and stability in visual perception

The human visual system recruits adaptation mechanisms that enhance perceptual sensitivity over time. However, such mechanisms can also introduce substantial repulsive biases, disrupting stable perceptual experiences. Research on serial dependence has suggested that the visual system promotes stability by mechanisms that integrate new sensory inputs with inputs obtained in the recent past, leading to an attractive bias to the past visual inputs. Yet, it remains unclear when and how the two mechanisms interact in visual processing. The present study tested the hypothesis that adaptation produces a repulsive bias during earlier processing, which is later mitigated by post-perceptual decisional processing. In two orientation perception tasks, observers used a mouse to reproduce the orientation of a briefly presented target. We recorded the mouse trajectory to track the temporal dynamics of their reproduction responses. We found that the mouse reports began more slowly when the current stimulus was similar to the prior stimulus. In the mouse-tracking data, the initial phase of the response exhibited a strong repulsive bias away from the prior stimulus, but this bias diminished significantly as the response unfolded, ending with either a weaker repulsive bias or a small attractive bias, depending on task contexts. These results indicate that post-perceptual decision processes are involved in both repulsive and attractive serial biases, suggesting that the visual system balances the competing demands of sensitivity and stability in perceptual experiences by reducing early repulsive biases through dynamic decisional mechanisms, thereby optimizing behavior in a given task context.