Prat-Carrabin Arthur, Gershman Samuel J
Department of Psychology and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA.
PNAS Nexus. 2025 Aug 29;4(9):pgaf275. doi: 10.1093/pnasnexus/pgaf275. eCollection 2025 Sep.
A classic result of psychophysics is that human perceptual estimates are more variable for larger magnitudes. This "Weber behavior," however, has typically not been the focus of the prominent Bayesian paradigm. Here, we examine the variability of a Bayesian observer in comparison with human subjects. In two preregistered experiments, we manipulate the prior distribution and the reward function in a numerosity-estimation task. When large numerosities are more frequent or more rewarding, the Bayesian observer exhibits an "anti-Weber behavior," in which larger magnitudes yield less variable responses. Human subjects exhibit a similar pattern, thus breaking a long-standing result of psychophysics. Nevertheless, subjects' responses are best reproduced by a logarithmic encoding of magnitudes, a proposal of Fechner often regarded as accounting for Weber behavior. We thus obtain an anti-Weber behavior together with a Fechner encoding. Our results suggest that the increasing variability may be primarily due to the skewness of natural priors.
心理物理学的一个经典结果是，人类的感知估计对于更大的量级来说变化更大。然而，这种“韦伯行为”通常并不是著名的贝叶斯范式的关注焦点。在这里，我们将贝叶斯观察者的变异性与人类受试者进行比较。在两项预先注册的实验中，我们在数量估计任务中操纵先验分布和奖励函数。当大数量更频繁或更有奖励时，贝叶斯观察者表现出“反韦伯行为”，即更大的量级产生的反应变异性更小。人类受试者表现出类似的模式，从而打破了心理物理学的一个长期结果。尽管如此，受试者的反应最好通过量级的对数编码来重现，这是费希纳的一个提议，通常被认为可以解释韦伯行为。因此，我们得到了一种反韦伯行为以及费希纳编码。我们的结果表明，变异性增加可能主要是由于自然先验的偏度。
