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Tao Gao, Joshua New, Brian Scholl; Perceived biological agency in a Slithering Snake animation. Journal of Vision 2011;11(11):217. doi: 10.1167/11.11.217.
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© 2015 Association for Research in Vision and Ophthalmology.
A central task for human vision is to detect the presence of animate agents in the local environment. In studies of perceived animacy, single geometric shapes move in patterns that elicit percepts of animacy and goal-directedness. In studies of biological motion, complex “point-light” body structures engage in highly specialized kinematics that elicit percepts of biological agency. Here we explore a possible midpoint between these phenomena with a novel display — the Slithering Snake animation — consisting of a line of small discs, each of which always maintains a short distance from its neighbors. The discs move according to an extremely simple algorithm: the head disc moves randomly, and each subsequent disc moves toward the disc in front of it. This display triggers a rich, compelling percept of snake-like biological agency. We explored the influence of the Slithering Snake on attention and perspective-taking, based on the treatment of the randomly-moving disc as the agent's “head”. First, in a probe detection task, we found that attention is automatically attracted to the head (compared with the center, or “tail”). This effect was due to perceived agency, and not to lower-level motion differences or predictability, since the effect (a) reversed when the animations played in reverse order; and (b) largely decreased or even disappeared when the endpoints moved identically, but the snake's middle was invisible or was a rigid line. Second, participants had to quickly identify whether a probe was presented to the left or right of the discs. Responses were slowed considerably when the snake's perspective conflicted with their own (as in a probe to the left of the discs, but to the right from the snake's perspective). These effects show how the perception of biological agency can be generated by surprisingly simple cues, and how such percepts automatically influence other perceptual and cognitive processes.
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