Goal congruency without stimulus congruency in bimanual coordination.

Two experiments explored the role of stimulus congruency and goal congruency for the generation of object-oriented actions with two hands. Participants had to place two objects into either parallel or opposite orientations by carrying out either symmetrical or asymmetrical forearm rotations. Performance was superior when the required object orientations were identical rather than different, almost independent of the symmetry of the required arm movements. In extending previous research, goal congruency effects ensued even under conditions in which congruency of imperative response signals could not have contributed to goal congruency effects, either because only a single stimulus was used to indicate the required goals in an individual trial (Experiment 1) or such stimuli were absent at all (Experiment 2). The results thus confirm the importance of goal codes for the reconcilableness of bimanual actions, and rule out accounts in terms of stimulus-related processes.