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Georgios Kountouriotis, Callum Mole, Natasha Merat, Peter Gardner, Richard Wilkie; Steering along curved paths is influenced by global flow speed not speed asymmetry. Journal of Vision 2015;15(12):416. doi: 10.1167/15.12.416.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal flow, the pattern of motion caused by self-motion through a textured world, is used to control steering. Our previous work has shown that flow asymmetries influence humans steering along demarcated paths, with different textures on either side of the path causing biases consistent with participants reducing flow asymmetries (Kountouriotis et al., 2013). To test whether asymmetries in speed also bias locomotor control, participants were asked to steer a series of curved trajectories in a virtual reality simulated environment. Regions of the ground plane either side of a visible bounded path were rotated at different speeds to create flow asymmetries. The manipulation varied (i) Asymmetry Direction: whether the ground to the inside of the bend moved slower or faster than the outside of the bend, (ii) Asymmetry Size: whether the difference in speeds of the two regions was a small gap or a large gap, and (iii) Global Flow Speed: whether the average speed across both regions was slower than, the same as, or faster than the actual locomotor travel speed. The results suggest that participants did not simply equalise the flow vectors (i.e. steer towards the slower-moving region) since asymmetry size and direction did not systematically alter steering. Instead, participants were influenced by the global flow speed, whereby faster global flow led to greater oversteer (towards the inside of the bend) and vice versa. Importantly, steering biases occurred despite the visible path providing splay angle information across all conditions. We conclude that global flow speed is used to control locomotor steering even when travelling along visible paths that provide alternative useful sources of information
Meeting abstract presented at VSS 2015
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