The following is a summary of “Effects of satisfying and violating expectations on serial dependence,” published in the February 2023 issue of Ophthalmology by Abreo, et al.

Serial dependence is the tendency for observers to overstate the similarity (attractive dependence) or, in some situations, the difference between a stimulus and a preceding stimulus (repulsive dependence). The importance of bottom-up sensory interactions has been highlighted by numerous investigations that have shown serial reliance on various modalities and stimulus properties. Comparatively, fewer studies have examined how expectations and other higher-level cognitive processes may affect serial reliance. For a study, by placing target brightness gratings after a series of non-target gratings, researchers were able to influence observers’ expectations. 

The sequence spun either predictably, creating expectations, randomly, creating none, or predictably, with an unpredictable target orientation (violating expectations). Although observers’ estimates of expected stimuli were less inaccurate and showed less uncertainty, their responses were biased away from the penultimate stimulus in the sequence (repulsive dependence). Yet, when random sequences followed replies, there was an appealing bias toward the penultimate stimulus. Surprising targets displayed a hybrid of the two biases so that when targets (by chance) came up as predicted, responses were repellent but were drawn to target orientations that more blatantly deviated from expectations. 

According to the findings, while it was possible that responding to random and unanticipated occurrences by being attracted to past stimuli was a default strategy, some expectations might actually make that default bias turn into one that’s repellent.