While serial dependence has been shown to depend on spatial attention toward the previous stimulus location (Fischer & Whitney, 2014), it has also been reported to occur when previous stimuli were task irrelevant (Fornaciai & Park, 2018a, 2018b), suggesting that attention to a particular stimulus feature is not necessary for serial dependence to occur. In particular, it is unclear how a previous stimulus needs to be processed in order to exert a serial-dependence bias in subsequent perceptual decisions. Consequently, the precise boundaries within which a stabilization of neural representations could take place are not known. Generally, the ubiquity of serial dependencies in perceptual decisions is striking and suggests that they might arise from a general computation of the brain, potentially reflecting the stabilization of neural representations.Īlthough serial-dependence biases have been observed in perceptual decisions about a variety of stimulus features, the conditions under which they arise are still elusive. Such serial-dependence biases may arise at different stages during the perceptual decision-making process (Bliss et al, 2017 Cicchini et al., 2017 Fornaciai & Park, 2018a Fritsche et al, 2017 Pascucci et al., 2019) and could perhaps jointly occur at multiple levels of stimulus processing (Kiyonaga, Scimeca, Bliss, & Whitney, 2017).
Such features include orientation (Cicchini, Mikellidou, & Burr, 2017 Czoschke, Fischer, Beitner, Kaiser, & Bledowski, 2018 Fischer & Whitney, 2014 Fritsche, Mostert, & de Lange, 2017), numerosity (Cicchini, Anobile, & Burr, 2014 Corbett, Fischer, & Whitney, 2011 Fornaciai & Park, 2018a), spatial location (Bliss, Sun, & D'Esposito, 2017 Manassi, Liberman, Kosovicheva, Zhang, & Whitney, 2018 Papadimitriou, White, & Snyder, 2017), visual variance (Suárez-Pinilla, Seth, & Roseboom, 2018), face identity (Liberman, Fischer, & Whitney, 2014), emotional expression (Liberman, Manassi, & Whitney, 2018), and attractiveness (Xia, Leib, & Whitney, 2016). In line with this idea, recent studies have found that perceptual decisions about a large variety of visual stimulus features are biased toward features encountered in the recent past. In particular, by leveraging information from the recent past, neural representations could be smoothed in time to compensate for perturbations which are not caused by genuine changes in the physical world (Burr & Cicchini, 2014). Theoretically, this temporal continuity could be exploited to stabilize neural representations. Importantly, our environment is relatively stable over short timescales and thus exhibits temporal continuity (Dong & Atick, 1995). This suggests separate sources of these positive and negative perceptual biases. Conversely, the repulsive bias for stimuli with large orientation differences was not modulated by feature-based attention. The attractive bias was markedly reduced-to less than half of its original magnitude-when observers attended to the size, rather than the orientation, of the previous stimulus. We found an attractive bias in orientation estimations when previous and current stimuli had similar orientations, and a repulsive bias when they had dissimilar orientations. Here we investigated whether focusing attention on particular features of the previous stimulus modulates serial dependence.
However, it is unclear under which circumstances previous input attracts subsequent perceptual decisions, and thus whether serial dependence reflects a broad smoothing or selective stabilization operation. Serial dependence may serve to stabilize neural representations in the face of external and internal noise. Perceptual decisions about current sensory input are biased toward input of the recent past-a phenomenon termed serial dependence.
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