Abstract
We routinely locomote through the world successfully, even at high speeds. At VSS2001 Wilkie & Wann presented evidence supporting the contribution of Retinal Flow (RF) and Visual Direction (VD) to the control of steering. When steering curved paths towards a target we observed that both RF and VD information could be used to perform the task successfully. It was still unclear whether there was any switching between information sources when there was a shift in their relative strengths. We investigated this in two ways:
We reduced the illumination of the scene to degrade RF information, and found that participants did rely more on VD information.
We examined steering behaviour over the time-course of individual trials to see if there were temporal shifts in information use. We split the trials into early (2–4s) and late (4–6s) steering and compared conditions with contrasting amount of RF and VD information. During early stages it was clear that both RF and VD could influencing steering, even when other veridical sources of information were present. By comparing the observed data with modelled data (using the model in Wilkie & Wann, 2002) it became apparent that there was a shift in weight from RF to VD between the early and late steering periods.
We conclude that the weighting of an information source is linked to its strength, and so reliance upon a source can be modified by degrading/enhancing the quality of that information. This shift seems to occur naturally over the time course of an approach to a steering target.