The addition of force feedback to virtual environments and teleoperators provides many benefits to the user. However, the mechanisms by which force feedback improves performance remain unknown. We present an experiment demonstrating that force feedback can provide a physical constraint to an operator?s motion, passively restraining the hand and reducing error even before the operator can voluntarily respond to the force stimulus. Because of the presence of force feedback, the magnitude of unwanted incursions into a virtual wall were reduced by up to 80%, as compared to the case with no force feedback. We also propose that a second order mechanical model of the operator?s hand can be used to quantify the benefits of force feedback. Using our model, we are able to account on average for over 95% of the variance in the force on the hand.