Eye movements during transitive action observation have sequential structure.

In this paper, we explore how observers of a reach-to-grasp action can identify and distinguish between the agent and patient (i.e. target) of the action. We investigate the hypothesis that there is a characteristic sequential structure to the observer's pattern of saccades, with the agent being fixated first, and then the target. We report an experiment which indicates that this sequence of saccades, while not ubiquitous, is overwhelmingly more likely than chance. The experiment also sheds some light on the mechanisms which allow the observer to saccade from the agent of the action to the target.