Epistemic actions alter the world so as to aid and augment cognitive processes such as recognition and search.
Merely pragmatic actions, by contrast, alter the world because some physical change is desirable for its own sake (e.g., putting cement into a hole in a dam).
In Tetris, falling geometric shapes must be rapidly directed into an appropriate slot in an emerging structure. A rotation button can be used. David Kirsh and Paul Maglio (1994) calculate that the physical rotation of a shape through 90 degrees takes about 100 milliseconds, plus about 200 milliseconds to select the button. To achieve the same result by mental rotation takes about 1000 milliseconds. Kirsh and Maglio go on to present compelling evidence that physical rotation is used not just to position a shape ready to fit a slot, but often to help determine whether the shape and the slot are compatible.
— Andy Clark, David Chalmers - The Extended Mind
experts tend to run their programs more frequently while debugging than novices do
— Usability Analysis of Visual Programming Environments - A "Cognitive Dimensions" Framework