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Jonathan Z. Bakdash, Jason S. Augustyn, Dennis R. Proffitt; Effects of effort and reduced visual cue information on percieved walking speed. Journal of Vision 2005;5(8):747. doi: 10.1167/5.8.747.
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Previous studies have shown that people can estimate walking speed from the rate of optic flow (Banton et al., in press). However, it is unclear whether these estimates are driven solely by the optical properties of the flow field or by additional factors. For example, Bhalla & Proffitt (1999) and Proffitt et al. (2003) showed that an observer's physiological potential for action can alter his or her perception of the slant of hills and of extents along the ground. Building on these findings, we hypothesized that perceived walking speed might also be affected by manipulations of physiological potential, specifically, effort for walking.
Participants walked on a treadmill while wearing a virtual-reality headset. The virtual environment (VE) consisted of an infinitely long moving walkway running through an airport concourse. As participants walked along the walkway through the world the rate of optic flow was varied randomly between 3 and 8 mph in 1 mph increments. The actual walking speed on the treadmill remained constant at 3 mph. For each trial, participants were asked whether the speed of the world matched their walking speed and perceived walking speed was determined by averaging speeds at which the participant responded, “yes”.
To manipulate walking effort physiological potential was changed by having participants walk with a heavy backpack or without a backpack in one of two VEs, which contained rich or impoverished optic flow cues. The rich optic flow VE contained detailed textures and objects and the impoverished VE had minimal textures and objects.
With impoverished optic flow the estimated walking speed was significantly higher for participants wearing a backpack versus participants that did not wear a backpack. Speed estimation was not affected by wearing the backpack in the rich optic flow condition. This finding suggests physiological potential is given greater weight in speed estimation as the availability of optical cues decreases.
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