Different as they appear at first glance, Arabic, Sanskrit, and 114 other writing systems share basic structural characteristics : characters with vertical symmetry (such as the Roman letters A and T) and a preference for vertical and horizontal lines over oblique lines ( like those of the letters X and W).
The explanation appears to be rooted in the wiring of our brains, according to this study .
How we see the letters
Common features cited in written language can take advantage of how our eyes and brains process images: neurons fire faster when viewing objects that show vertical symmetry, such as human faces, and horizontal and vertical lines, which are common in natural landscapes .
To support this idea, Olivier Morin , a cognitive anthropologist at the Max Planck Institute for the Science of Human History in Jena, Germany, analyzed the characteristics of 116 writing systems over 3,000 years of history. So-called logographic writing systems such as Chinese and Sumerian cuneiform, which have too many characters and are too visually complex to be easily analyzed, were left out.
Morin and his team of researchers thus classified more than 5,500 characters and calculated the number of vertical, horizontal and oblique lines. They also measured how many characters formed mirror images if they were divided in half vertically or horizontally, properties known as vertical and horizontal symmetry.
Morin found, on average, that about 61% of the lines in all the scripts were horizontal or vertical , more than chance would predict. (That number rises to 70% for the Latin alphabet, which is used to write English or Spanish.) And vertically symmetric characters accounted for 70% of all symmetric characters.
Together, the findings suggest that humans are drawn to these characteristics in writing, and that this is caused by the way our brains process information.
But did written scripts evolve to have more of these characteristics over time, as users of the language selected certain forms and orientations from a script? To find out, Morin examined a subset of 93 scripts that descended from, or gave rise to, another script in the study.
Morin ultimately found no evidence that hyphens tend to become more horizontal or vertical over time, suggesting that the scribes who created them integrated human preferences into the written word from the beginning. That is in contrast to claims that human preferences act as a kind of selective pressure on writing, forcing it to evolve to become more readable or die.