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Huai-Yong Zhao, Peng Wang, Ai-Shi Jiang, Ling-Dan Wu, Hong-Jin Sun; Estimation of distance on flat and uphill terrains using visual matching and blind walking task. Journal of Vision 2008;8(6):752. doi: 10.1167/8.6.752.
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© ARVO (1962-2015); The Authors (2016-present)
We tested whether participants in a natural environment judged distances up a hill to be different from that on a flat ground and whether the same distance would be estimated differently by perception or action tasks. The experiment was conducted in an outdoor environment with both flat and uphill (8 degrees) terrains. In Experiment 1, participants first viewed a target distance (6, 8, 10, 12, or 14 m) on a flat ground or on a hill and then produced that distance through blind walking task (BWT), again either on the flat ground or uphill, with a total of four stimulus-response (view-walk) combinations (flat-flat, flat-hill, hill-flat and hill-hill). The results indicated that participants significantly overshot distance when they first viewed a distance on the flat ground and then walked uphill. This overshoot was not seen in the other three conditions. In Experiment 2, following a visual preview of target distances, in addition to responding by walking, participants also matched two self-to-target distances by verbally instructing an experimenter to position a target at a distance representing the previewed distance. While the overshoot in BWT was seen again in uphill walk following the preview on flat surface, the overestimation was not seen in distance matching task. The overestimation in uphill condition was also not found in Experiment 3, in which participants were given a distance value then were asked to produce that distance by adjusting their self-to-target distance in either flat ground or uphill condition. The results of these three experiments suggest that the overshoot might not be due to errors in the perception of target distance on a hill; instead it might be the result of errors in perceptual motor transformation during a less familiar mode of motor action (walking uphill) when the terrains are different during stimulus and response.
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