An illustration of the UCM concept for the task of producing a constant value of the sum of the outputs of two effectors: E1 + E2 = C. The UCM is shown with the thick dashed line with negative slope, while the orthogonal direction (ORT) is shown as a thick, solid line. If a person performs this task many times, the cloud of data points is expected to represent an ellipse elongated along the UCM. If a person is asked to produce a quick change in the performance variable and then return to the previous value, the new state will show deviations both along the UCM (motor equivalent, ME) and orthogonal to the UCM (on-motor equivalent, nME); ME > nME is expected.