The use of blank and text targets might suggest that differences in postural sway might result from the difference in the visual stimuli (i.e., the targets), rather than differences in the visual tasks. In effect, this would mean that postural sway was affected by the type of texture in optical flow. Postural responses to optical flow are known to be influenced by flow geometry , and motion parallax. However, no existing theory of postural control predicts that posture should be influenced by the two-dimensional texture of the visible environment, and similar types of postural responses have been observed of a wide variety of target patterns, such as random squares, checkerboards, and simulated marble.Finally, postural responses to optical flow are known to be robust even when the visual targets are defocused to the limits of static pattern detection. Thus, there is no reason tosuspect that posture would be affected by the variation in the appearance of the visual targets.