GENERALIZED MOTOR PROGRAMS AND SCHEMAS FOR MOVEMENT
Editor's Remarks (Chapters 8 and 9)
In Chapters 8 and 9, Richard Schmidt treats us to an indepth discussion of the nature of motor programs and their interaction with peripheral feedback. Schmidt draws several distinctions that seem of heuristic value. One is between slow and fast movements, research into which allows one to differentiate between the types of errors that people make during movement. More important perhaps is that a clearer definition of the motor-program concept emerges. In Schmidt's view, because of feedback processing limitations, errors of program selection cannot be corrected within short periods of time. On the other hand, errors in execution can be handled by low-level peripheral reflex adjustments without any need to alter the program itself.
This analysis, as Schmidt admits, is only part of the story. How, one asks, are we to account for the remarkable context sensitivity of the action system? There must be lawful statements that we can make about how environmental information is used during the course of activity. One of the most elegant experiments in the movement literature discussed by Schmidt in Chapter 8 shows that a spinal cat walking on a treadmill produces different reactions to the same stimulus (a tap to the paw), depending on where in the step cycle the stimulus is applied. Schmidt analogizes this behavior to an IF statement in the computer language