Thursday, April 16, 2009

What does not cause veering; what does not help

Kallie, Schrater, and Legge seem to be good at telling us what does not cause veering: inexperience walking without vision; and they tell us what does not help: an explicit indicator of intended walking direction and a skill for curvature detection. Here are some excerpts:

What causes this veering behavior? Our research suggests that a simple explanation, unperceived motor noise at the level of individual steps, may explain the veering behavior of blind pedestrians and sighted pedestrians who are blindfolded. (p. 183)
A pedestrian’s ability to walk a straight line depends on the availability and quality of sensory information about walking direction (Loomis & Beall, 1998; Philbeck, Loomis, & Beall, 1997; Rieser, Ashmead, Talor, & Youngquist, 1990) and on the capacity to execute movements in an intended direction. (p. 184)
Although blind walkers often use acoustic or tactile cues during walking, those cues are often uninformative and sometimes misleading. For that reason, we asked what factors limit straight-line walking in the absence of visual, acoustic, or tactile cues. (p. 184)
The lack of difference in veering behavior between sighted and blind participants suggests that a history of visual experience is not critical to performance on this task. (p. 187)
The results of the present experiment do not support the hypothesis that people who veer the least by the previously mentioned measures are most sensitive to path curvature. For emphasis of this
point, the participant (P3) who was best at curvature detection (threshold radius = 36.48 m) also was the one who veered the most in the straight-line-walking task (mean unsigned deviation 
1.73 m). (p. 188-189)
An explicit indicator of intended walking direction did not reduce veering behavior. In fact, in the case of the static perceptual pointer condition, veering actually increased compared with the physical alignment condition, in which there was no explicit pointer. The increased veer is due mainly to a larger linear component in the participants’ trajectories. (p. 191-192)

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