Human tool-use: a causal role in plasticità of bodily and spatial representations.

Along the evolutionary history, humans have reached a high level of sophistication in the way they interact with the environment. As humans, we are able to modify, adapt and shape the world around us according to our needs. One important step in this process has been the introduction of tools enabling humans to go beyond the boundaries of their physical possibilities. If it’s true that we share tool-use abilities with several other species like non human primates (Peeters et al 2009; Povinelli et al, 2009), birds (Weir et al, 2002) and rodents (Bird and Emery, 2009; Okanoya et al, 2008, Emery and Clayton, 2009), in humans this capacity is uniquely developed (Johnson-Frey, 2003). Ontogenetically, not only we are able to skillfully use tools that we know how to build, but we can also use tools we can’t build or even invent: Not all of us know how to make a fork or a pen, despite the fact that these are among the simplest tools we use without any effort in our everyday life. The acquisition of tool-use abilities is of great importance as it multiplies the ways we can interact with the external word. One obvious consequence is that the large use of instruments makes our relation with the environment mediated and less direct, a characteristic that can be comparable to the effect produced by using language. Moreover, if in animals the construction and use of instruments is related (and quite exclusively tested) in a context of problem solving, human beings are the only species in which cultural components have deeply infiltrated tool construction, tool-use and even social desirability of tool-use. In most of western cultures, for example, we can accept that a baby eats with her hands, but can’t accept the same from an older child and surely not from an adult. The result of most of the tools we use is to separate ourselves from Nature, that is very different from animal tool-use. Behind the complex phenomenon of phylogenetic development of tool-use and its potential causal implication for higher forms of cognition, there are important “lower-level” aspects of cognition that highlight tool-use plays a causal role in shaping both spatial and bodily representations, and this is the focus of the present chapter. First, we will offer a definition of tool and in particular of what can be called tool-use in our perspective, for operational purposes. Second, we will focus on the causal role that tool-use plays in producing changes on space perception and body representation. Third, we will discuss the challenges tool-use presents for the sensorimotor system of the human and non human primate brain.