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Grace Roessling, Brett Fajen; Hybrid versus unified accounts of affordance perception and on-line control during locomotor interception. Journal of Vision 2020;20(11):1299. doi: https://doi.org/10.1167/jov.20.11.1299.
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Most real-world locomotor interception tasks involve both affordance perception and on-line visual regulation. Affordance perception is critical for knowing whether a moving target is catchable and worth pursuing. Fajen (2013) proposed that the perception of catchability relies on “affordance-based information” about the speed needed to intercept in relation to one’s maximum possible speed. Visual regulation entails continuous, on-line guidance of locomotor speed and direction. According to most accounts, actors rely on so-called “current-future information” such as the change in bearing angle, which specifies whether one will intercept the target in the future if current conditions persist. Taken together, this implies a hybrid account of locomotor interception according to which the perception of catchability and on-line visual guidance are treated as separate processes that rely on different sources of information. The aim of this study was to explore through modeling and simulation the behavior that emerges from such a hybrid strategy in the context of a complex locomotor interception task. We used Matlab to create a model of this strategy and simulated it for a task that required the agent to both accurately perceive whether targets were catchable and regulate speed and direction of locomotion to intercept targets. We also modeled an alternative unified strategy that relies entirely on affordance-based information for both pursuit decisions and on-line guidance. By this account, the agent pursues catchable targets by moving in a direction that allows for interception while traveling as close as possible to its preferred speed. The behavior that emerged from both strategies was compared to that exhibited by human subjects performing the same task. We demonstrate that a hybrid strategy that relies entirely on current-future information after movement initiation cannot account for behavior and that affordance perception plays a role in both pursuit decisions and on-line visual guidance.
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