Ocular tracking of biological and nonbiological motion: the effect of instructed agency.

Recent findings suggest that visuomotor performance is modulated by people's beliefs about the agency (e.g., animate vs. inanimate) behind the events they perceive. This study investigated the effect of instructed agency on ocular tracking of point-light motions with biological and nonbiological velocity profiles. The motions followed either a relatively simple (ellipse) or a more complex (scribble) trajectory, and agency was manipulated by informing the participants that the motions they saw were either human or computer generated. In line with previous findings, tracking performance was better for biological than for nonbiological motions, and this effect was particularly pronounced for the simpler (elliptical) motions. The biological advantage was also larger for the human than for the computer instruction condition, but only for a measure that captured the predictive component of smooth pursuit. These results suggest that ocular tracking is influenced by the internal forward model people choose to adopt.