One particularly important continuous skill is tracking, in which the performer's limb movements control a lever, a wheel, a handle, or some other device to follow the movements of some target-track, with steering wheel movements made so the car follows the track, defined by the roadway. Tracking movement are very common in real-world skills situations,and mush research has been directed to their performance and learning. Tracking tasks are sometimes scored using a particular error score, called root-mean-square error (RMSE) presented in detail in Focus on Research 1.3, "Error Scores in Continuous Tasks.