ABSTRACT
In 1995, an aftereffect following treadmill running was described, in which people would inadvertently advance when attempting to run in place on solid ground with their eyes closed. Although originally induced from treadmill running, the running-in-place after-effect is argued here to result from the absence of sensory information specifying advancement during running. In a series of experiments in which visual information was systematically manipulated, aftereffect strength (AE), measured as the proportional increase (post-test/pre-test) in forward drift while attempting to run in place with eyes closed, was found to be inversely related to the amount of geometrically correct optical flow provided during induction. In particular, experiment 1 (n=20) demonstrated that the same aftereffect was not limited to treadmill running, but could also be strongly generated by running behind a golf-cart when the eyes were closed (AE=1.93), but not when the eyes were open (AE=1.16). Conversely, experiment 2 (n=39) showed that simulating an expanding flow field, albeit crudely, during treadmill running was insufficient to eliminate the aftereffect. Reducing ambient auditory information by means of earplugs increased the total distances inadvertently advanced while attempting to run in one place by a factor of two, both before and after adaptation, but did not influence the ratio of change produced by adaptation. It is concluded that the running-in-place aftereffect may result from a recalibration of visuomotor control systems that takes place even in the absence of visual input.