Our commentary addresses two issues that are not developed enough in the target article. First, the model does not clearly address the distinction among external objects, external body parts, and internal bodies. Second, the authors could have discussed further the role of body schema with regard to its dynamic character, and its role in perspective and in imitation.
The author describes and sociocognitive skills that he argues as being necessary for tool use. We propose that those skills could be based on simpler detection systems humans could share with other animal tool users. More specifically, we discuss the impact of object affordances on the understanding and the social learning of tool use.
In his article Grush proposes a potentially useful framework for explaining motor control, imagery, and perception. In our commentary we will address two issues that the model does not seem to deal with appropriately: one concerns motor control, and the other, the visual and motor imagery domains. We will consider these two aspects in turn.