Go with the flow

Abstract

In a recent article, Wann and Land cast rhetorical aspersions upon the idea that optic flow is used to guide human locomotion1. They were especially critical of the notion that the perception of heading (one's instantaneous direction of translation) from optic flow is required for locomotor control in general, and for the task of steering a curved trajectory in particular. Their argument strikes us as full of straw, for to our knowledge no one has actually proposed that heading is required for all locomotor tasks, and researchers have already identified other variables that could be used to steer a curved path to a goal. In this reply we urge the gentle reader not to be swayed by the authors’ disputation, and we bring to bear some empirical evidence that rules out their data-free conjectures.