Serial Dependence in Human Visual Perception and Decision-Making

Decisions about a current visual stimulus are systematically biased by recently encountered stimuli, a phenomenon known as serial dependence. In human vision, for instance, we tend to report the features of current images as more similar â i.e., an attractive bias â or more different â i.e., a repulsive bias â to those seen a few seconds earlier. While the phenomenology is clear-cut, the nature and underlying mechanisms have continued to be hotly debated for decades.

In this thesis, I first provide an extensive review of the main research paradigms, the key factors determining the two opposite biases, and the theories about the underlying mechanisms of serial dependence. The review also focuses on the challenge of establishing a relationship between serial dependence and the concept of object continuity, specifically whether serial dependence assists in maintaining the perceptual continuity of visual features and objects.

Second, I investigate whether serial dependence selectively applies to low-level visual features and objects, and whether it integrates past and present information to form a more accurate perception by reducing current uncertainty, as suggested by Bayesian accounts. My findings reveal that serial dependence does neither selectively apply to low-level features nor to objects. Moreover, I demonstrate that the integration of past and present information does not facilitate perception by reducing current uncertainty.

Third, I further examine the role of the number of intervening stimuli and task relevance, in addition to the time interval between current and past stimuli, which has often been considered a criterion for serial dependence. The findings here indicate that serial dependence is modulated by an interplay of time, the number of stimuli, and task relevance, suggesting that no single criterion or general temporal tuning can independently define serial dependence.

Last, I explore the format of history in serial dependence â what propagates from the past to the present â to determine whether it is the mere history of visual stimuli or the history of internal representations that is integrated. My findings support the latter, demonstrating that serial dependence arises from internal representations, wherein diverse visual features are condensed into the essential formats required by a given task.

Taken together, serial dependence is an intriguing yet complex phenomenon. The research I present in this thesis highlights its influence on visual information processing at various stages and its simultaneous modulation by multiple factors during a task, resisting simplification into a single criterion.