From a paper titled The Extended Mind by Clark and Chalmers:
Thus consider the use of pen and paper to perform long multiplication (McClelland et al 1986, Clark 1989), the use of physical re-arrangements of letter tiles to prompt word recall in Scrabble (Kirsh 1995), the use of instruments such as the nautical slide rule (Hutchins 1995), and the general paraphernalia of language, books, diagrams, and culture.
Ducks and Economics 