Center for Visual Science, University of Rochester, Rochester, NY 14627-0270, USA.
Proc Natl Acad Sci U S A. 2013 Mar 12;110(11):E1064-73. doi: 10.1073/pnas.1214869110. Epub 2013 Feb 25.
Because of uncertainty and noise, the brain should use accurate internal models of the statistics of objects in scenes to interpret sensory signals. Moreover, the brain should adapt its internal models to the statistics within local stimulus contexts. Consider the problem of hitting a baseball. The impoverished nature of the visual information available makes it imperative that batters use knowledge of the temporal statistics and history of previous pitches to accurately estimate pitch speed. Using a laboratory analog of hitting a baseball, we tested the hypothesis that the brain uses adaptive internal models of the statistics of object speeds to plan hand movements to intercept moving objects. We fit Bayesian observer models to subjects' performance to estimate the statistical environments in which subjects' performance would be ideal and compared the estimated statistics with the true statistics of stimuli in an experiment. A first experiment showed that subjects accurately estimated and used the variance of object speeds in a stimulus set to time hitting behavior but also showed serial biases that are suboptimal for stimuli that were uncorrelated over time. A second experiment showed that the strength of the serial biases depended on the temporal correlations within a stimulus set, even when the biases were estimated from uncorrelated stimulus pairs subsampled from the larger set. Taken together, the results show that subjects adapted their internal models of the variance and covariance of object speeds within a stimulus set to plan interceptive movements but retained a bias to positive correlations.
由于存在不确定性和噪声，大脑应该使用场景中物体统计的准确内部模型来解释感觉信号。此外，大脑应该根据局部刺激环境中的统计数据来调整其内部模型。以打棒球为例。视觉信息的匮乏使得击球手必须利用有关先前投球的时间统计和历史知识，来准确估计投球速度。我们使用打棒球的实验室模拟来测试一个假设，即大脑使用对象速度统计的自适应内部模型来规划手的运动以拦截移动物体。我们通过贝叶斯观察者模型拟合了被试的表现，以估计被试在理想表现的统计环境下的表现，并将估计的统计数据与实验中刺激的真实统计数据进行了比较。第一项实验表明，被试准确地估计和使用了刺激集中对象速度的方差来调整击球行为的时间，但也表现出了次优的序列偏差，对于随时间不相关的刺激来说是次优的。第二项实验表明，即使从更大的刺激集中抽取不相关的刺激对来估计序列偏差，序列偏差的强度也取决于刺激集中的时间相关性。总的来说，这些结果表明，被试调整了刺激集中对象速度的方差和协方差的内部模型，以计划拦截运动，但仍保留了对正相关的偏差。
