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Nikolaus F. Troje, Stephanie Lau; Perceived naturalness of human motion depends on internal consistency. Journal of Vision 2012;12(9):466. doi: 10.1167/12.9.466.
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© ARVO (1962-2015); The Authors (2016-present)
Human motion is constrained by inertial and gravitational forces. In order to move energetically efficient our motor control systems must take these constraints into account when producing body movements. For instance, when changing walking speed a whole array of associated kinematic parameters also change their values. These changes are subtle but systematic and we hypothesize that the visual system knows about them and evaluates them when visually assessing another persons movements. The motion of 50 male and 50 female participants was captured while they were walking on a treadmill at three different speeds (veridical speeds). Each sample was then presented as a point-light display and played back at the same three speeds (playback speeds). In that way, we created for each of the 100 walkers a set of 9 point-light displays (3 veridical x 3 playback speeds), only three of which displaying the person at the same speed at which he/she was recorded. Observers were then asked to use a Likert scale to rate how natural the displays appeared. Significant main effects of veridical speed and playback speed were found. The highest veridical speed and the medium playback speed were perceived to be most natural. Most importantly, we found a highly significant interaction between these two factors, indicating that observers very sensitively detected the inconsistencies between veridical speed and playback speed. Displays in which veridical and playback speed matched were always rated to be the most natural. This impressive sensitivity to the very subtle dependency of the kinematics of walkers on their speed demonstrates that the visual system employs implicit knowledge about the biomechanic relations between different kinematic parameters. It also exposes the level of sophistication required for biomechanical models that can generate convincingly realistic character animation in computer graphics.
Meeting abstract presented at VSS 2012
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