Cognitive theory suggests that human beings have two fundamental modes of reasoning: logical (albeit however informally some folks may do that when left to their own devices) and spatial.Stillings, N.A., M.H. Feinstein, J.L. Garfield, [et al.]. 1991. Cognitive Science: An Introduction. Cambridge, MA: MIT Press. 533 p. Interesting things happen when logic is implemented graphically.
