In 2 experiments, we evaluated relations between postural activity and the amplitude of visually guided eye movements. Participants shifted their gaze to follow horizontal oscillation of a visible target. The target moved with amplitude 9° or 24°. In different experiments, the frequency of target oscillation was 0.5 Hz or 1.1 Hz. In both experiments, the variability of head and torso motion was reduced (in the anterior-posterior axis) when participants viewed moving targets, relative to sway during viewing of stationary targets. Sway variability was not influenced by the amplitude of target motion. The results are compatible with the hypothesis that postural activity was modulated relative to the demands of suprapostural visual tasks.
Bibliographical noteFunding Information:
Portions of the data were presented at a meeting of the International Society for Ecological Psychology (Cincinnati, OH, 2006) and at the 14th International Conference on Perception and Action (Yokohama, Japan, 2007). Preparation of this article was supported by Enactive Interfaces, a network of excellence (IST Contract 002114) of the Commission of the European Community; the National Science Foundation (BCS-0236627 to T. Stoffregen and SES-0728743 and BCS-0926662 to M. Riley); the University of Montpellier-1; and the Institut Universitaire de France. We thank Sebastien Villard for help with data reduction and analysis.