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Richard M. Wilkie, John P. Wann; Looking to your future path: is heading off on a tangent?. Journal of Vision 2002;2(7):626. doi: https://doi.org/10.1167/2.7.626.
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© ARVO (1962-2015); The Authors (2016-present)
There has been an assumption that the perception of ‘heading’ when passively observing linear motion tells us something about the information we use when steering ourselves along curved paths through the world. There are, however, two broad ways of categorising the information that can be derived from retinal flow in order to guide steering: ‘heading’ or ‘path’. ‘Heading’ refers to the instantaneous rectilinear direction of motion of the observer, but this is constantly changing when travelling on a curved path. In contrast, ‘path’ encompasses the future curvilinear course through the world. It has been hard to dissociate these two representations since in principle both could be derived from retinal flow information. Here we investigate our ability to judge both ‘heading’ and ‘path’ during motion on a curved path over a computer generated tarmac ground plane. We asked observers to look at their ‘path’ or instantaneous ‘heading’, and recorded point of gaze (PoG) during each trial. The results showed that observers where significantly more accurate at looking at their ‘path’ (∼3°) than their ‘heading’ (∼8°). This suggests that an accurate representation of instantaneous ‘heading’ is not available to an observer of curvilinear flow, whereas instantaneous ‘path’ information is present. The implication for models of steering are discussed.
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