Suelzenbrueck, S. 1 , Sutter, C. 2 & Ladwig, S. 2
1 Project Group Transformed Movement, IfADo - Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany
2 Work and Cognitive Psychology, RWTH Aachen University, Germany
The ideomotor principle holds that actors select, initiate and execute movements by activating the anticipatory codes of the movements' sensory effects. These may be representations of body-related effects and/or representations of more distal effects. When using tools effects in body space and distant space often do not correspond or are even in conflict. Previous studies have demonstrated that distal action effects dominate action control, while body-related effects play a minor role. In this talk we present a line of experiments in which we address the conditions and limitations of the distal predominance in action control. In a closed loop task of sensorimotor control different gains perturbed the relation between hand movements on a digitizer tablet and cursor movements on a display. Concerning motor control the data showed that the human brain adapt to small changes in visuomotor gain without being aware of the changes in gain or in one's own movement. When provided with explicit information about the occurrence of gain changes adjustments were stronger than implicit adjustments. The larger adjustments observed with cued gain changes resulted from both explicit and implicit motor adjustments occurring at the same time. We further observed that participants were generally extremely uncertain about the trajectory of their hand movements when using such tools. We discuss whether the low awareness of one's own movements originates from an insufficient quality of the humans' tactile and proprioceptive system or from an insufficient spatial reconstruction of this information in memory.