A contrast effect between the concurrent production and perception of movement directions

Abstract

With three experiments, we explored the nature of specific interference between the concurrent production and perception of movements. Participants were asked to move one of their hands in a certain direction while simultaneously trying to identify the direction of an independent and non-biological stimulus motion. Perceived direction of the stimulus was assessed with either above/below judgements (Experiment 1), same/different judgements (Experiment 2), or the adjustment of a line (Experiment 3). The results revealed a form of contrast effect: Perceived directions were repulsed by produced directions. Moreover, the size of the effect was comparable across the three experiments, which points to its robustness and allowed us to control for potential confounds associated with some of the perceptual measures. These results alleviate concerns regarding the interpretation of related findings and demonstrate that effects of this type are not tied to the processing of biological motion, as previously proposed.

Acknowledgements

Portions of this work were previously presented at the 47th Tagung experimentell arbeitender Psychologen [Experimental Psychology conference], Regensburg, Germany, April 2005, and the 14th conference of the European Society for Cognitive Psychology, Leiden, The Netherlands, September 2005. We would like to thank two anonymous reviewers for valuable comments, Wilfried Kunde for providing code to collect data from the graphics tablet, Fiorello Banci for technical support, Rafael Laboissière for assistance with the maximum-likelihood fitting procedures, Rolf Ulrich for insightful discussions, and Silvia Bauer and Cornelia Maier for help with running the participants. Marc Grosjean is now at the Institute for Occupational Physiology at the University of Dortmund, Ardeystrasse 67, 44139 Dortmund, Germany.

Notes

¹This choice of Ms and RSs was necessary to reliably measure specific interference effects of production on perception. As a consequence, however, the current paradigm did not allow us to obtain a similar measure for effects of perception on production. That is, given that all of the RSs lay on the same “side” of the Ms, any potential influence of the perceived motions on the produced movements could not be interpreted in terms of assimilation or contrast.

²The fact that this difference only reached significance with a one-tailed test led us to corroborate this result with a different, nonparametric, estimation method: The Spearman-Kärber method (Miller & Ulrich, 2001, 2004; Ulrich & Miller, 2004), which does not make any assumptions about the underlying psychometric functions. When comparing the PSEs obtained with this method, the t-test reached significance two-tailed, t(13) = 3.02, p<.05.