Serwe Sascha, Drewing Knut, Trommershäuser Julia
Department of Psychology, Justus Liebig University Giessen, Germany.
J Vis. 2009 May 28;9(5):28.1-14. doi: 10.1167/9.5.28.
We present experimental and computational evidence for the estimation of visual and proprioceptive directional information during forward, visually driven arm movements. We presented noisy directional proprioceptive and visual stimuli simultaneously and in isolation midway during a pointing movement. Directional proprioceptive stimuli were created by brief force pulses, which varied in direction and were applied to the fingertip shortly after movement onset. Subjects indicated the perceived direction of the stimulus after each trial. We measured unimodal performance in trials in which we presented only the visual or only the proprioceptive stimulus. When we presented simultaneous but conflicting bimodal information, subjects' perceived direction fell in between the visual and proprioceptive directions. We find that the judged mean orientation matched the MLE predictions but did not show the expected improvement in reliability as compared to unimodal performance. We present an alternative model (probabilistic cue switching, PCS), which is consistent with our data. According to this model, subjects base their bimodal judgments on only one of two directional cues in a given trial, with relative choice probabilities proportional to the average stimulus reliability. These results suggest that subjects based their decision on a probability mixture of both modalities without integrating information across modalities.
我们提供了实验和计算证据，用于估计在向前的、视觉驱动的手臂运动过程中的视觉和本体感觉方向信息。我们在指向运动的中途同时且单独地呈现了有噪声的方向本体感觉和视觉刺激。方向本体感觉刺激由短暂的力脉冲产生，其方向不同，并在运动开始后不久施加到指尖。在每次试验后，受试者指出刺激的感知方向。我们测量了仅呈现视觉刺激或仅呈现本体感觉刺激的试验中的单峰表现。当我们呈现同时但相互冲突的双峰信息时，受试者的感知方向落在视觉和本体感觉方向之间。我们发现判断的平均方向与最大似然估计（MLE）预测相符，但与单峰表现相比，可靠性并未显示出预期的提高。我们提出了一种替代模型（概率线索切换，PCS），该模型与我们的数据一致。根据该模型，受试者在给定试验中仅基于两个方向线索之一做出双峰判断，相对选择概率与平均刺激可靠性成正比。这些结果表明，受试者基于两种模态的概率混合做出决策，而不是跨模态整合信息。
