Brains operate using perception-action cycles. Good programmers know that a key to fast code is a good data structure. Sensory inputs are like a data structure for the brain. Using your body and physical implements, you can shape the sensory data structure that your brain uses. Moving around to get a good look is thinking on your feet. Tinkering is thinking with your hands. If you just use your head to think, you’re mentally handicapped.
Tetris game play provides a good case study of how the brain and hands work together. Careful study of play indicates that players rotate the falling blocks more frequently than is plausible for a linear cognitive program of play. Study also indicates that using keystrokes, a player can rotate a falling block about ten times as fast as a person can mentally rotate such a block. In figuring out where to direct a block, players use keystrokes to rotate blocks at least in part because doing so is more cost effective than performing such actions on representations within one’s head.
Trade-offs between external sense and cognitive effort also occurs in choices between different sensory forms of media. The rapid shift of “soap operas” from radio to television suggests that adding visual stream to the programming lowered the cost of making sense of it. More generally, the cost of making sense of presence falls with richer sensory inputs.
Playing Tetris and making sense of presence both involve perception-action cycles. In Tetris, the player rotates blocks to create new sensory inputs so that higher level cognitive processes can more efficiently plan trajectories for placing blocks. In sense of presence, attunement to another occurs as a good created through the social evolution of human nature. This attunement can occur at different cognitives levels, from awareness of twittering of another to a face-to-face, heart-to-heart talk with a best friend. At each level, attunement is associated with characteristic patterns of action such as textual response or eye-tracking.
Perception-action cycles are built into human biology from the lowest to the highest levels of cognitive complexity. As a cognitive scientist explained:
At all levels of the central nervous system, the processing of sensory-guided sequential actions flows from posterior (sensory) to anterior (motor) structures, with feedback at every level. Thus, at cortical levels, information flows in a circular fashion through a series of hierarchically organized areas and connections that constitute the perception-action cycle. Automatic and well-rehearsed actions in response to simple stimuli are integrated at low levels of the cycle, in sensory areas of the posterior (perceptual) hierarchy and in motor areas of the frontal (executive) hierarchy. More complex behavior, guided by more complex and temporally remote stimuli, requires integration at higher cortical levels of both perceptual and executive hierarchies, namely areas of higher sensory association and prefrontal cortex.
Interactivity, which new Internet services emphasize, is deeply embedded in human biology.
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 David Kirsh and Paul Maglio (1994), “On distinguishing epistemic from pragmatic actions,” Cognitive Science 18, pp. 15-20.
 Id. p. 24.
 Joaquín M. Fuster (2004), “Upper processing stages of the perception-action cycle,” TRENDS in Cognitive Sciences, vol. 8, no. 4 (April) p. 144. Note that id. Figure 2 describes the general structure of Kirsh and Maglio (1994), p. 39, Figure 16. For additional description of the perception-action cycle, see Paul Baxter’s Memoirs of a Postgrad.