Perception of the end position of a limb loaded with a weight

We examined the effect of loading a weight on the perception of the end position of the limb. The participants haptically perceived where the end of their limb was located while they swung the limb or statically held it. The results showed that the loading of a weight influenced participants' perception only when they swung the limb; when the weight was attached to a participant's hand, the position was perceived to be farther from the body than when the weight was attached to the forearm or no weight was attached. We also found that the end position was generally underestimated when the participants swung their limb. On the other hand, when the participants statically held their limb, the perceived position was not affected by the loading of the weight and was rather precise. These results suggest that the perceptual system for limb end position is sensitive to changes in the surrounding haptic information caused by moving the limb.