Kirsh and Maglio [2] distinguish between ‘epistemic’ and ‘pragmatic’ actions. An epistemic action is an action whereby users change their environment to search for a solution or strategy to perform a certain task. A pragmatic action is strictly the action needed to actually perform this task. Kirsh and Maglio illustrate this with the example of how players of the game, Tetris, rapidly rotate the falling bricks instead of mentally determining the correct position for a brick and then rotating it to the correct position. Players use epistemic actions to modify the environment which helps them to determine the correct position. They can do this faster than the corresponding mental rotations. It might be easier to physically modify the external world and then interpret it rather than compute and interpret a new state internally.
