Abstract:

Serial dependence effect (SDE) refers to a stable and systematic attractive bias in which cognitive processing of the current stimuli is pulled toward the stimuli presented moments ago. Existing studies have revealed many factors modulating serial dependence effects. The first one is attention. Only stimuli that are consciously perceived can produce serial dependence effects. Secondly, sensory uncertainty of stimuli also affects serial dependence effects. Particularly, previous studies had found that stimuli with higher sensory uncertainty produced higher SDE intensity. The physical characteristics of stimuli also affect serial dependence effects. In addition, the spatial and temporal distances between the neighboring stimuli also have a tuning effect on serial dependence effects. All these distinctive features and special effects (caused perception bias, but did not influence reaction times) showed that the serial dependence effect is a brand new "history effect" (the influence of past stimuli on the current stimulus).

The cognitive and neural mechanisms of serial dependence effects have received much attention. There are currently several mainstream views since 2014. The earliest view, i.e., the “continuity field” theory, believes that serial dependence is an effect purely at the perceptual level and occurs before the stage at which sensory signals are transformed into conscious representations. Some researchers also believe that serial dependence effects occur at the perceptual level and further they are modulated by neural feedback signals from higher levels. Another view attributes serial dependence effects to dynamic biases in working memory, while some researchers believe that serial dependence effects stem from decision-making processes. Finally, some researchers propose that serial dependence effects may exist at multiple cognitive processing stages and cannot be explained by a single mechanism. Recently, empirical progress had been made upon the neural mechanism of serial dependence effects. For example, Electroencephalogram (EEG) studies had revealed electrophysiological signals that can represent serial dependence effects starting from early stages of perceptual processing in adaptation paradigms. Evidence from fMRI studies also demonstrated an attractive bias at the level of early sensory representation imposed by previous perceptions. The latest research had discovered abnormal serial dependence effects in patients with brain injury. In addition, it was found that the dorsal premotor cortex had significant influence on visual movement-based serial dependence. The underlying mechanism of serial dependence effects is being uncovered gradually.

Since been proposed, the serial dependence effect is thought to be a mechanism that promotes stability for visual processing by integrating visual input along the temporal dimension. However, some results are still controversial. Thus, there is still large space left for studies on serial dependence effects. In the future research, it is necessary to tackle the origin of serial dependence effects with multiple strategies, including innovation of experimental paradigms, data analysis approaches, and various cognitive neuroscience technologies. Further, future studies can focus on the modulating factors on serial dependence effects, and provide explanations to inconsistent results and individual differences of serial dependence effects in previous studies. Finally, it is also important to note that any psychological experimental design involving sequential visual stimuli in the future will have to consider the potential effects of serial dependence that may exist between past and current stimuli.

Key words: serial dependence effect, cognitive and neural mechanisms, perception, memory, decision