To me or to you? When the self is advantaged.

The present study aimed at verifying whether and why sequences of actions directed to oneself are facilitated when compared to action sequences directed to conspecifics. In experiment 1, participants reached to grasp and brought a piece of food either to their own mouth for self-feeding or to the mouth of a conspecific for feeding. In control conditions, they executed the same sequence to place the piece of food into a mouth-like aperture in a flat container placed upon either their own mouth or the mouth of a conspecific. Kinematic analysis showed that the actions of reaching and bringing were faster when directed to the participant's own body, especially for self-feeding. The data support the hypothesis that reaching to grasp and bringing to one's own body and, in particular, one's own mouth for self-feeding, form an automatic sequence, because this is the result of more frequent execution and coordination between different effectors of one's own body, such as arm and mouth. In contrast, the same sequence directed toward a conspecific is not automatic and requires more accuracy probably because it is guided by social intentions. This hypothesis was supported by the results of control experiment 2 in which we compared the kinematics of reaching to grasp and placing the piece of food into the mouth of a conspecific (i.e. feeding) with those of reaching to grasp and placing the same piece of food into a mouth-like aperture in a human body shape (i.e. placing). Indeed, the entire sequence was slowed down during feeding when compared to placing.