Conceptual Binding: Integrated Visual Cues Reduce Processing Costs in Bimanual Movements

1 Motor Control Lab, Department of Biomedical Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium; and 2 Movement Neuroscience Laboratory, Department of Sport and Exercise Science and 3 Department of Medicine, University of Auckland, Auckland, New Zealand Submitted 30 September 2008; accepted in final form 13 April 2009 In discrete reaction time (RT) tasks, it has been shown that nonsymmetric bimanual movements are initiated slower than symmetric movements in response to symbolic cues. By contrast, no such RT differences are found in response to direct cues ("direct cue effect"). Here, we report three experiments showing that the direct cue effect generalizes to rhythmical bimanual movements and that RT cost depends on different cue features: 1 ) symbolic versus direct or 2 ) integrated (i.e., action of both hands is indicated as one entity) versus dissociated (i.e., action of each hand is indicated separately). Our main finding was that dissociated symbolic cues were most likely processed serially, resulting in the longest RTs, which were substantially reduced with integrated symbolic cues. However, extra RT costs for switching to nonsymmetrical bimanual movements were overcome only when the integrated cues were direct. We conclude that computational resources might have been exceeded when the response needs to be determined for each hand separately, but not when a common response for both hands is selected. This supports the idea that bimanual control benefits from conceptual binding. Address for reprint requests and other correspondence: N. Wenderoth, FABER, KU Leuven, Tervuursevest 101, 3001 Heverlee (Leuven), Belgium (E-mail: nici.wenderoth{at}faber.kuleuven.be )