Humans can often conduct both linear and nonlinear control tasks after a sufficient number of trials, even if they initially do not have sufficient knowledge about the system's dynamics and the way to control it. Theoretically, it is well known that some nonlinear systems cannot be stabilized asymptotically by any linear controllers. However, there is a possibility that human may use a linear control scheme for nonlinear control tasks. The hypothesis proposed in this paper is that humans switch the linear controllers with a virtual constraint. Each controller is responsible for a small region where the linear approximation can work well for nonlinear tasks. It is suggested that the proposed virtual constraint can play an important role to overcome a limitation of the linear controllers.