A number of metaphors have been suggested: we “offload” some of our thinking onto our surroundings, or we incorporate objects in such a way that they come to act like prosthetics. The point is that to understand human cognition, it is a mistake to focus only on what goes on inside the skull, because our abilities are highly “scaffolded” by environmental props—by technologies and cultural practices, which become an integral part of our cognitive system.4
