Reading pervades every aspect of our daily lives, so much so that one would be hardpressed to find a room in a modern house without words written somewhere inside. Many of us now read more sentences in a day than we listen to. Not only are we highly competent readers, but our brains even appear to have regions devoted to recognizing words. A Martian just beginning to study us humans might be excused for concluding that we had evolved to read. But, of course, we haven’t. Reading and writing is a recent human invention, going back only several thousand years, and much more recently for many parts of the world. We are reading using the eyes and brains of our illiterate ancestors. Why are we so good at such an unnatural act? Here I describe recent evidence that, although we have not evolved to be good at reading, writing appears to have culturally evolved to be good for the eye. More specifically, recent research supports the exciting hypothesis that human visual signs look like nature, because that is what we have evolved over millions of years to be good at seeing. This ecological hypothesis for letter shape not only helps explain why we are such good readers, but answers the question, Why are letters and other visual signs shaped the way they are?

Natural to the Eye

The topological shapes of non-pictorial visual signs are, then, for the eye, not the hand. But we are still left with the question, Why does the eye like these shapes? Here is where the evolutionary, or ecological, hypothesis enters into the story. Because over millions of years of evolution our visual systems have been selected to be good at processing the conglomerations of contours occurring in nature, I reasoned that if visual signs have culturally evolved to be easy to see, then we should expect visual signs to have natural topological shapes. Where are these topological shapes in nature? What were conglomerations of strokes for visual signs are now conglomerations of contours for natural scenes. Contours are the edges of objects (as seen by the eye), not, of course, strokes in the world. For example, an L occurs in the world when exactly two edges of an object meet at their endpoints, like an elbow. A T occurs in the world when the edge of an object goes behind another object in the foreground. A Y occurs, for example, at the inside corner of a rectangular room.

We measured how common these and the other topological shapes occur in natural scenes, and were stunned to find that nature possesses the shape signature we saw earlier for visual signs. That is, visual signs are shaped like nature, confirming our ecological hypothesis for the shapes of visual signs. If visual signs look like nature, one might first suppose that the shape signature of nature depends significantly on which natural environment one considers. However, to our surprise, we found that the shape signature is highly robust, differing hardly at all whether we measured images of ancestral environments (e.g., tribal villages, savannas) or urban environments (buildings, walkways).

Because of the robust topological notion of shape we used in our analysis, any environment with opaque objects strewn about will tend to have the same shape signature.

This underlies why the diverse kinds of visual sign have a similar signature despite the diverse environments from which they spring, and one may speculate that aliens might for this reason possess visual signs that look reminiscent of our own.

Read on the fascinating article: Scientific Blogging