Individuals are adept at estimating average properties of group visual stimuli, even following brief presentations. In estimating the directional heading of walking human figures, judgments are biased in a peculiar manner: groups facing intermediate directions are perceived to be more leftward- or rightward-facing than actual averages. This effect was previously explained as a repulsive bias away from a central category boundary; groups along this boundary (directly facing the observer) are estimated with lower variability and with relatively greater accuracy. Here we show that: (i) the original effect replicates and is constant over time in a novel estimation task with persistent directional states; and, (ii) novel patterns of response variability and durations align with the entire range of overestimation. A simple model of additive errors proportional to viewer uncertainty matches the observed bias magnitudes. We furthermore show that the bias generalizes beyond approaching walkers with the use of rearward-facing walkers presented at a nonparallel angle. Overall, the recurring relation between bias and uncertainty is also consistent with top-down and post-perceptual causes of misestimation.

个人擅长估计群体视觉刺激的平均特性，即使是在简短的演示之后。在估计行走人物的方向性时，判断会以一种特殊的方式出现偏差：面对中间方向的群体被认为比实际平均值更向左或向右。这种效应以前被解释为远离中心类别边界的排斥偏差。沿此边界（直接面向观察者）的组以较低的可变性和相对较高的准确度进行估计。在这里，我们表明：（i）在具有持久方向状态的新估计任务中，原始效果会随着时间的推移而复制并保持不变；(ii) 反应变异性和持续时间的新模式与整个高估范围一致。与观察者不确定性成比例的加性误差的简单模型与观察到的偏差幅度相匹配。我们进一步表明，通过使用以非平行角度呈现的后向步行者，这种偏见可以推广到接近步行者之外。总体而言，偏见和不确定性之间反复出现的关系也与自上而下和后知觉的错误估计原因一致。