Expectations strongly affect and shape our perceptual decision-making processes. Specifically, valid expectations speed up perceptual decisions, and determine what we see in a noisy stimulus. Despite the well-established effects of expectations on decision-making, whether and how they affect low-level sensory processes remain elusive. To address this problem, we investigated the effect of expectation on temporal thresholds in an individuation task (detection of the position of an intact image, a house or face). We found that compared to a neutral baseline, thresholds increase when the intact images are of the unexpected category, but remain unchanged when they are of the expected category. Using a recursive Bayesian model with dynamic priors we show that delay in sensory processes is the result of further processing, consequently longer time, required in case of violated expectations. Expectations, however, do not alter internal parameters of the system. These results reveal that sensory processes are delayed when expectations are not met, and a simple parsimonious computational model can successfully explain this effect.

期望强烈影响和塑造我们的感知决策过程。具体来说，有效的期望会加速知觉决策，并决定我们在嘈杂的刺激中看到什么。尽管期望对决策的影响已经确立，但它们是否以及如何影响低水平的感觉过程仍然难以捉摸。为了解决这个问题，我们研究了期望对个性化任务（检测完整图像、房子或人脸的位置）中的时间阈值的影响。我们发现，与中性基线相比，当完整图像属于意外类别时，阈值会增加，但当它们属于预期类别时，阈值保持不变。使用具有动态先验的递归贝叶斯模型，我们表明感觉过程的延迟是进一步处理的结果，因此需要更长的时间，在违反预期的情况下需要。然而，期望不会改变系统的内部参数。这些结果表明，当期望没有得到满足时，感觉过程会延迟，一个简单的简约计算模型可以成功地解释这种效应。