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Justin Owens, William Warren; Are attentional resources required to anticipate moving obstacles?. Journal of Vision 2009;9(8):1128. doi: 10.1167/9.8.1128.
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Avoiding moving obstacles is critical to our ability to locomote safely. Further, it may be advantageous to anticipate which environmental objects are likely to get in our way, particularly when traveling at high speeds (as in driving). Fajen & Warren (2003, 2007) proposed an on-line dynamical model of locomotor behavior that requires no higher-level planning or anticipation. However, recent experiments have shown that people can learn to anticipate the trajectory of a moving obstacle, though only when necessary to avoid an immanent collision (Owens & Warren, VSS 2007, 2008). Here we present two studies that investigate whether visuo-spatial attentional resources are required to learn to anticipate moving obstacles.
Participants walked in a virtual environment while wearing a head-mounted display (60° H × 47° V), and head position was recorded with a sonic/inertial tracker (70 ms latency). In Study 1, participants performed a modified Brooks Letter Task while walking to a visible goal, and were instructed to avoid moving obstacles. En route to the goal, some obstacles would veer to impede their path. In the Predictable block of trials, all obstacles' trajectories were cued by their appearance, whereas in the Random block the trajectory was independent of appearance. We found that the secondary task impaired participants' ability to anticipate obstacles in the Predictable block, but only when that block was presented first. When the Random block was presented first, practice on the secondary task allowed anticipatory avoidance in the Predictable block.
For Study 2, we increased the difficulty of the secondary visuo-spatial task. The results showed increased impairment of obstacle anticipation and greatly reduced practice effects, such that locomotor paths were consistent with the dynamical control model. We conclude that visuo-spatial attentional resources are required for anticipatory control of locomotion, and that interference with these resources returns locomotion to on-line control.
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