Title: The need for speed: global optic flow speed influences steering. Kountouriotis, G., K., Mole, C., D., Merat, N., & Wilkie, R., M.
Title: The need for speed: global optic flow speed influences steering [pdf]Paper  abstract   bibtex   
How do animals move along paths? Different species are sensitive to optic flow and one control solution is to ensure flow symmetry in visual fields; however, it is unclear whether animals do this when taking curved paths. Flow asymmetries alter the global properties of flow (i.e. flow speed) which could also influence steering control. We tested humans steering curved paths in a virtual environment. The scene was manipulated so that the ground plane to either side of the visible path produced large or small asymmetries in optic flow. Independent of asymmetries and the locomotor speed, the scene properties were altered to produce either faster or slower globally averaged flow speeds. Results showed that rather than being influenced by flow asymmetries, steering responded to global flow speed. We conclude that the human brain performs global averaging of flow speed from across the scene and uses this signal as an input for steering control. This finding is surprising since the visible path provided all the necessary information required to steer, whereas the global flow speed (by itself) did not. To explain these findings existing models of steering must be modified to include a new perceptual variable: namely global optic flow speed.

Downloads: 0