Article Kirsh, D. (2010). Thinking with external representations. Ai & Society, 25(4), 441-454. Seven ways external representations enhance cognitive power: Change the cost structure of inferential landscape (Lower the cost of controlling thought - they help coordinate thought) Provide a structure that can serve as a shareable object of thought Create persistent referents Facilitate re-representations Often more natural representation of structure than mental representations Facilitate the computation of more explicit encoding of information Enable the construction of arbitrarily complex structure "One way of making the in principle case is to show that there are operations that can be performed on external representations that cannot be performed on internal representations, and that, somehow, these are essential." "There are cognitive things we can do outside our heads that we simply cannot do inside. On those occasions, external processes function as special cognitive artifacts that we are incapable of simulating internally." "So, for most people, to make sense of music the first thing to do is to play it or listen to it. This raises a further requirement on the elements of thought. If a representational system is to function as a medium of thought, the elements in the system must be sufficiently manipulable to be worked with quickly." "Models have a special role in thinking, and can for our purposes be seen as two, three, or even four-dimensional external representations: paper sketches—2D; cardboard models, cartoons, and fly-throughs—3D models in space or time; and dynamically changing three-dimensional spatial structures—4D models."