Role of stiffness in weight perception.

Here, we focused on a load-on task to clarify the judgment mechanism for weight perception. We measured hand trajectory and surface electromyography to estimate time-varying stiffness and torque patterns in joints. Our results showed that the goal of learning motor skills under load-on tasks is to maintain the hand position, and that humans produce force with cocontraction and increasing stiffness levels according to the weight of an object. Finally, we examined whether stiffness is an effective parameter as an efferent signal for weight perception and found that stiffness plays an important role in weight perception. [ABSTRACT FROM AUTHOR]