Epistemic action: a measure for cognitive support in tangible user interfaces?
Paper in proceedings, 2008
In the field of Human-Computer Interaction the usability of a program or tool is often measured in terms of efficiency, effectiveness, and satisfaction . Recently, in the field of Tangible User Interfaces (TUIs) an additional measure for the quality of tangible tools was introduced: epistemic action. Kirsh and Maglio  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. It has been suggested that epistemic action is a relevant concept when researching computer interfaces that involve physical objects such as TUIs . Sharlin et al.  suggest that support for epistemic actions is an important factor in the success of a TUI. In this paper we look at three different spatial planning tools and aim to relate the traditional measures of efficiency, effectiveness, and satisfaction with the number of epistemic actions to determine whether this last measure can additionally be a useful measure of quality for TUIs.