Cognitive tools shape thought: diagrams in design.

Thinking often entails interacting with cognitive tools. In many cases, notably design, the predominant tool is the page. The page allows externalizing, organizing, and reorganizing thought. Yet, the page has its own properties that by expressing thought affect it: path, proximity, place, and permanence. The effects of these properties were evident in designs of information systems created by students Paths were interpreted as routes through components. Proximity was used to group subsystems. Horizontal position on the page was used to express temporal sequence and vertical position to reflect real-world spatial position. The permanence of designs on the page guided but also constrained generation of alternative designs. Cognitive tools both reflect and affect thought.