A man-machine interaction experiment in the real-time continuous control sense is presented. The computer program is given and described, together with some representative results with regard to plant order, display effects and training effects. In particular, the importance of the selection of the displayed variable is emphasized. The experiment has been helpful in the appreciation of the effects of display gain selection and the inclusion of the derivative terms in the displayed variable, as well as demonstrating the importances of plant order and operator training, by allowing time response shape and criterion value comparisons. The nature of the conclusions reached can be generalized to automatic control, helping students of control systems.