Centre for Brain and Mind, Department of Psychology, University of Western Ontario, London, Canada.
Exp Brain Res. 2010 Aug;205(2):283-8. doi: 10.1007/s00221-010-2353-9. Epub 2010 Jul 8.
When lifting objects of identical mass but different sizes, people perceive the smaller objects as weighing more than the larger ones (the 'size-weight' illusion, SWI). While individual's grip and load force rates are rapidly scaled to the objects' actual mass, the magnitude of the force used to lift these SWI-inducing objects is rarely discussed. Here, we show that participants continue to apply a greater loading force to a large SWI-inducing cube than to a small SWI cube, lift after lift. These differences in load force persisted long after initial errors in grip and load force rates had been corrected. Interestingly, participants who showed the largest illusion made the smallest errors in load force. This unexpected relationship suggests that the motor system is consistently biased toward the expectations of heaviness for a particular stimulus in a Bayesian fashion, and that this loading error is subsequently reduced by SWI perceptual errors in the opposite direction.
当人们举起质量相同但大小不同的物体时，他们会感觉到较小的物体比较大的物体更重（“大小重量”错觉，SWI）。虽然个体的握力和负载力速率会迅速与物体的实际质量成比例缩放，但很少有人讨论用于举起这些产生 SWI 诱导物体的力的大小。在这里，我们表明，参与者会继续对大的 SWI 诱导立方体施加更大的加载力，而不是对小的 SWI 立方体施加更大的加载力，一次又一次。在最初纠正握力和负载力速率的误差后，这些负载力的差异仍然存在。有趣的是，表现出最大错觉的参与者在负载力上的误差最小。这种意外的关系表明，运动系统以贝叶斯的方式一致地偏向于对特定刺激的沉重感的期望，并且这种加载误差随后会被相反方向的 SWI 感知误差所减小。
