As I talked previously, "Epistemic actions: physical actions that make mental computations easier, faster ore more accurate". David Kirsh claims that "sometimes the best way to solve a cognitive problem is by adapting the world rather than adapting oneself". He relates this to Backman's work about complementary strategies:

Complementary strategies, therefore, allow agents to compensate for resource limitations in working memory and processing power, and cognitive limitations in categorizing skill, and so on. (Backman et al, 92).

... use of external representation in problem solving... There is a nice example about this in a japanese paper about finger counting (Hiroyuki Nakahara : Finger Counting as a Calendar: a case of distributed cognition).

...Bauer and Johnson-Laird (1993) hypothesised that an external representation can ease deductive reasoning in supporting the subject to keep track of the possible alternatives model (we're here in the 'mental model' theory). They validated this hypothesis and claimed that the subjects do not perform all the computation in their minds but they solve the problem by interacting with the representation... According to Rizzo and Marti, this experiment (from johnson-laird and bauer) is the first ever done to show that external representation is a support of distributed processing between mind and representation.