Using Proportions and Grids in Logo Design

Mathematically a proportion is defined as a four-term relation among quantities: A is to B as C is to D. In essence, the task of proportional reasoning is to compare the relation between one pair of terms (or quantities) with the relation between the other pair. One of the simplest examples of proportional reasoning occurs in the identification of shapes. Even young children can tell whether two shapes are equally proportioned, in terms of the ratios of their heights to their widths for instance—even if they are very different in overall size.

What Eye-Movements Tell Us About Ratios and Spatial Proportions by Catherine Sophian and Martha E. Crosby