ABSTRACT
People know a lot about the shapes of objects, they have few words in any language to describe shapes. There are a few terms like “smooth versus rough” or “pointy versus rounded” that imprecisely describe differences. But for the most part, instead of adjectives, people use nouns. The geometric definition of a circle is straightforward: the locus of points equidistant from a center. But an alternative definition that might be considered is a shape whose diameter in all directions is the same. Measuring the diameter of a feature in many directions would then provide an easy procedure by which to recognize a circular shape. Human vision is a complex process and a rich subject for study. The visual system involves processing in the eyes, the visual cortex, and other parts of the brain. The literature, which includes physiology, psychology, and many other fields, is vast.
