Effects of sensorimotor transformations with graphical input devices

The impact of sensorimotor transformations with graphical input devices is surveyed with regard to action control. Recent evidence lets us assume that the distal action effect (the moving cursor) rather than the proximal action effect (the moving hand) determines the efficiency of tool use. In Experiment 1, different gains were explored with a touchpad and a mini-joystick. In correspondence with our assumptions the results revealed evidence that Fitts' law holds for distal action–effect movements, but less for proximal action–effect movements. Most importantly, this was not only true for the touchpad but also for the mini-joystick. We further found a more efficient use of the touchpad in comparison to the mini-joystick when a high gain was used. In Experiment 2, the dominance of the action effect on motor control was confirmed in an experiment with a digitiser tablet. The tablet amplitude was held constant, but again, movement times followed the perceived index of difficulty on the display. It is concluded that Fitts' law did not rely on the movements of the motor system, but on the distal action effects on the display (changes in visual space). Distal action–effect control plays an important role in understanding the constraints of the acquisition and application of tool transformations.