Abstract
Perceptual decisions are biased by recent perceptual history – a phenomenon termed ‘serial-dependence.’ Although ubiquitous and affecting our everyday perceptual decisions, the specific conditions that give rise to serial-dependence are not fully understood. Here, we investigated what aspects of perceptual decisions lead to serial dependence, and disambiguated the influences of low-level sensory information, prior choices and motor actions on subsequent perceptual decisions. Participants performed a visual location discrimination task in which they reported whether a brief stimulus (filled circle) lay to the left or to the right of the screen center. Test trials were preceded by several prior trials, designed to induce short-term biases, with varying degrees of relevance to the subsequent decisions. Following a short series of biased location discriminations, subsequent location discriminations were biased toward the prior choices. This attractive bias remained even when the prior and test choices were reported via different motor actions (using different keys), and when the prior and test stimuli differed in color. By contrast, prior discriminations about an irrelevant stimulus feature (color) did not substantially influence subsequent location discriminations, even though these were reported via the same action (motor biasing). Additionally, when color (not location) was discriminated, a bias in prior stimulus locations no longer substantially influenced subsequent location decisions. Hence, a key factor for serial-dependence is the degree of relevance between prior and subsequent perceptual decisions. These findings suggest that serial-dependence reflects a high-level mechanism by which the brain predicts and interprets new incoming sensory information in accordance with relevant prior choices.
Significance statement Recent perceptual experience influences subsequent perceptual decisions. In this study we investigated what elements of perceptual decisions contribute to this process. We found that choices themselves (rather than the sensory or motor elements) bias subsequent perceptual decisions. Such that, subsequent choices are more likely to be the same as prior choices. But, this only occurs when the prior and current perceptual decisions are about the same stimulus feature. Also, serial-dependence occurs irrespective of how, or whether, choices are reported. Hence, the degree of relevance between prior and subsequent perceptual decisions is a key factor underlying serial-dependence. These results suggest that the brain uses a high-level, predictive, mechanism to interpret new sensory information to be consistent specifically with relevant prior choices.