One function of perceptual systems is to construct and maintain a reliable representation of the environment. A useful strategy intrinsic to modern “Bayesian” theories of perception1, 2, 3, 4, 5, 6 is to take advantage of the relative stability of the input and use perceptual history (priors) to predict current perception. This strategy is efficient1, 2, 3, 4, 5, 6, 7 but can lead to stimuli being biased toward perceptual history, clearly revealed in a phenomenon known as serial dependence.8, 9, 10, 11, 12, 13, 14 However, it is still unclear whether serial dependence biases sensory encoding or only perceptual decisions.^15,16 We leveraged on the “surround tilt illusion”—where tilted flanking stimuli strongly bias perceived orientation—to measure its influence on the pattern of serial dependence, which is typically maximal for similar orientations of past and present stimuli.^7,10 Maximal serial dependence for a neutral stimulus preceded by an illusory one occurred when the perceived, not the physical, orientations of the two stimuli matched, suggesting that the priors biasing current perception incorporate the effect of the illusion. However, maximal serial dependence of illusory stimuli induced by neutral stimuli occurred when their physical (not perceived) orientations were matched, suggesting that priors interact with incoming sensory signals before they are biased by flanking stimuli. The evidence suggests that priors are high-level constructs incorporating contextual information, which interact directly with early sensory signals, not with highly processed perceptual representations.

感知系统的一个功能是构建和维护环境的可靠表示。现代“贝叶斯”感知理论 1、2、3、4、5、6 固有的一个有用策略是利用输入的相对稳定性并使用感知历史（先验）来预测当前感知。这种策略是有效的 1, 2, 3, 4, 5, 6, 7 但可能导致刺激偏向于知觉历史，这在称为连续依赖的现象中清楚地揭示了。8, 9, 10, 11, 12, 13, 14然而，尚不清楚串行依赖是偏向感觉编码还是仅偏向感知决策。^{15 , 16}我们利用“环绕倾斜错觉”——倾斜的侧翼刺激强烈地偏向感知方向——来测量它对连续依赖模式的影响，这对于过去和现在刺激的相似方向通常是最大的。^{7 , 10}当两个刺激的感知方向（而不是物理方向）匹配时，发生在幻觉刺激之前的中性刺激的最大连续依赖性，这表明偏向当前感知的先验包含幻觉的影响。然而，当它们的物理（未感知的）方向匹配时，中性刺激引起的虚幻刺激的最大串行依赖性发生，这表明先验与传入的感觉信号相互作用，然后再受到侧翼刺激的影响。证据表明，先验是包含上下文信息的高级构造，它们直接与早期感觉信号交互，而不是与高度处理的感知表征交互。