Testing the Ability to Represent and Control a Contact Force

While the concept of force is solidly grounded in Newtonian mechanics, it is not known if it is also represented in a consistent way by our brains as they control interactions of the hand with external objects. For example, a force of 10 N applied against different springs will cause different amounts of displacement. Are we able to represent 10 N in a way that is independent of the effects of applying such force to different objects? Here, we developed a simple method to address this question by engaging subjects in a task whose success depends critically upon the ability to exert a fixed force against different simulated springs. Our preliminary findings indicate that while this task is difficult, subjects learn after some training to exert the same force against different springs and in different directions.