Flanagan J Randall, Bittner Jennifer P, Johansson Roland S
Department of Psychology and Centre for Neuroscience Studies, Queen's University, Kingston, ON K7L 3N6, Canada.
Curr Biol. 2008 Nov 25;18(22):1742-7. doi: 10.1016/j.cub.2008.09.042.
The expectation that object weight increases with size guides the control of manipulatory actions [1-6] and also influences weight perception. Thus, the size-weight illusion, whereby people perceive the smaller of two equally weighted objects to be heavier, is thought to arise because weight is judged relative to expected weight that, for a given family of objects, increases with size [2, 7]. Here, we show that the fundamental expectation that weight increases with size can be altered by experience and neither is hard-wired nor becomes crystallized during development. We demonstrate that multiday practice in lifting a set of blocks whose color and texture are the same and whose weights vary inversely with volume gradually attenuates and ultimately inverts the size-weight illusion tested with similar blocks. We also show that in contrast to this gradual change in the size-weight illusion, the sensorimotor system rapidly learns to predict the inverted object weights, as revealed by lift forces. Thus, our results indicate that distinct adaptive size-weight maps, or priors, underlie weight predictions made in lifting objects and in judging their weights. We suggest that size-weight priors that influence weight perception change slowly because they are based on entire families of objects. Size-weight priors supporting action are more flexible, and adapt more rapidly, because they are tuned to specific objects and their current state.
物体重量随尺寸增加的预期指导着操纵动作的控制[1 - 6]，并且也影响重量感知。因此，人们会感知到两个等重物体中较小的那个更重，这种尺寸 - 重量错觉被认为是由于重量是相对于预期重量来判断的，对于给定的一类物体，预期重量会随着尺寸增加[2, 7]。在这里，我们表明重量随尺寸增加的基本预期可以通过经验改变，它既不是天生固定的，也不会在发育过程中固化。我们证明，连续多天练习举起一组颜色和质地相同、重量与体积成反比的积木，会逐渐减弱并最终反转用类似积木测试的尺寸 - 重量错觉。我们还表明，与尺寸 - 重量错觉的这种逐渐变化形成对比的是，感觉运动系统能迅速学会预测反转的物体重量，如举力所示。因此，我们的结果表明，在举起物体和判断其重量时所做的重量预测基于不同的适应性尺寸 - 重量图谱或先验知识。我们认为，影响重量感知的尺寸 - 重量先验知识变化缓慢，因为它们基于整个物体类别。支持动作的尺寸 - 重量先验知识更灵活，适应更快，因为它们针对特定物体及其当前状态进行了调整。
