The mirror is not enough: The case of complementary actions [Quando il mirror non basta. Il caso delle azioni complementari]

Human beings come into the world wired for social interaction. As has been observed in mimicry, priming, and automatic imitation, indeed, humans are remarkably efficient at resonating with one another. In specific contexts that require incongruent, complementary (from Latin complemèntum; i.e., that fills up) rather than imitative forms of interaction, nevertheless, motor resonance with the observed action can be an unsuitable response. In the case, for example, that someone hands us a mug by its handle with a precision grip, we will automatically, without thinking, grab the mug using a whole-hand-grasp (the most suitable grasping gesture in this particular situation). The types of grasps adopted by the two interacting agents are incongruent, but functionally appropriate. This example illustrates the importance of complementary actions in the context of the action–perception domain, and it encourages us to take a look at what is taking place behind the scenes and to question the mechanisms classically thought to be involved in motor resonant responses (e.g., the mirror system). In this article I shall review recent data unveiling this aspect, which have increased our knowledge on the flexibility of the human motor system in social contexts.