Why do letters look the way they do?

Posted on by rwwiley
What do the shapes on the left all have in common? What about those on the right? (Pictured, from top: Roman, Greek, Hebrew, Arabic, and Devanagri scripts.)

When you look at this image, do you know what all of the shapes on the left have in common? How about the shapes on the right?

If you know how to read more than one of those languages, then you may think the answer is that they represent the same sound, or have the same name. While that’s not a bad answer, what would you think if I told you that what all of the shapes on the left have in common is that they all came from a drawing of an ox? And on the right, a drawing of a house?

The shapes above on the left originally were a representation of an ox, and those on the right a house! Can you see the resemblance?

This is true because of how many of the world’s writing systems evolved—through a process where the earliest written symbols were pictographic or ideographic. That basically means that the most ancient forms of writing represented an idea by drawing an image to represent it… the shape of an ox’s head to represent “ox”, or the outline of a house to represent “house”.

Although the details are lost to history, researchers do know that over time these shapes became abstracted away from their origins as obviously visual representations. Instead of a symbol representing a whole word or an idea, they started to represent the smallest units of human language: “phonemes”, the basic pieces of our words. It is this evolution that allowed a drawing of an ox, which was called “alep” or “alef” in ancient Semitic languages, to represent just the first sound of that word—and why the language you are reading right now calls this letter “A”!

A drawing of an ox’s head (“alep”) becomes more abstract, and stands in for just the first sound–“a”. If you turn this familiar letter, “A”, upside down, you can still see the ox’s head.

Of course, this evolution of what written symbols represent does not explain why our shapes look the way they do—while it’s pretty easy to see how an “A” looks like an ox, it’s not so obvious for other letters. And indeed, some letters (or entire writing systems, like Korean Hangul) never began as depictions of real objects. While it’s hard to say with certainty why the shapes of our letters are what they are, some fascinating research suggests a couple of probable factors that drove our distant ancestors to create the shapes that they did. 

In Mesopotamia, the cuneiform writing system was produced using a stylus on clay tables (top), whereas in Egypt hieroglyphs were carved into stone or inked onto papyrus (middle), and in China free-flowing forms developed with the use of brushes (bottom). Notice that early shapes (top rows) look like pictures of the actual objects, but with time (lower rows) they became more abstract–in both appearance and meaning.

One of those historical factors is the medium in which the language was written. If you’ve ever tried to sign your name on a painting using a brush, or chisel it into a sculpture, you know that the tools you use have a major impact on what you are able to create. Cultures that prominently used clay or stone to write were likely influenced by those media in a way that lead to very different types of shapes than those that used ink and brushes—and the advent of the printing press or, in more recent times, computers, lead also to fundamental changes in typography.

Intersecting lines and curves are all around us. Can you see the T’s, L’s, V’s, Y’s, etc., all over this scene?

Another possible factor that may explain the shapes of our letters comes from nature. Some researchers have argued that the prevalence of certain shapes across different languages, like L-shapes and T-shapes, are a reflection of what shapes we encounter naturally in our environment (Changizi et al., 2006). Think about how a tree trunk meets the ground to form an upside-down T-shape, or how the shoreline of a lake creates a C-shape. It turns out that such intersections which naturally occur more often are also more common in writing systems across the world and history (so for example, shapes like L are very common, but shapes like A are less so).

Watch a short clip of Hubel and Wiesel’s classic experiment.

One last clue as to why our shapes look the way they do comes from what we know about brain activity in response to viewing letter-shapes like this. In visual cortex (the occipital lobe), there are neurons that respond preferentially to certain types of stimulation, which we call “visual features”. Pioneering experiments by Hubel & Wiesel in the 1960’s helped pave the way for understanding this basic phenomenon. There are groups of neurons that become particularly excited when they see lines of certain orientations, for example responding much more to a line at 45° then a line at 0° (horizontal); other neurons may prefer lines that intersect each other like in an X; still others, to closed circles like O as opposed to open ones like C. This property of visual cortex most have evolved not for the purposes of reading, but rather for recognition of objects and scenes—and it is consistent with the possibility that our letters tend to use the same shapes as those we see frequently in our environment!

References/Further reading:

• Changizi, M. A., Zhang, Q., Ye, H., & Shimojo, S. (2006). The structures of letters and symbols throughout human history are selected to match those found in objects in natural scenes. The American Naturalist, 167(5), E117–E139.

• Hubel, D. H., & Wiesel, T. N. (1968). Receptive fields and functional architecture of monkey striate cortex. The Journal of Physiology, 195(1), 215–243.

• Daniels, P. T., & Bright, W. (Eds.). (1996). The world’s writing systems. Oxford University Press on Demand.

What makes an ‘A’ an ‘a’?

Posted on by rwwiley

How are we able to identify what an object is, just by looking at it? If you were to describe to a young child what the letter ‘A’ looks like, you might talk about it having three lines like a triangle, two of them leaning toward each other, etc. But do you think you could come up with a single description that explains why all of the shapes in the figure above are an uppercase ‘A’? Surely not—yet nonetheless, we can seemingly tell without effort that we are looking at a chart of the uppercase letter ‘A’, and not some other letter or shape. How do we do this?

Arguably the most straight-forward way would be for us to simply memorize each instance of the letter ‘A’ that we have seen, and “label” in our memory, so to speak, as examples of that letter. But consider all of the different ‘A’s we have seen—different fonts, different sizes, styles, different people’s handwriting—we would have to memorize thousands upon thousands of shapes for each letter! This burden on our memory would be inefficient to the point of absurdity, and this theory of letter recognition (called “template matching”) has largely become discounted.

Roman letter features
Fig. 2 taken from Fiset, D., Blais, C., Ethier-Majcher, C., Arguin, M., Bub, D. N., & Gosselin, F. (2008). Features for uppercase and lowercase letter identification. Psychol. Sci.

The best research on this question generally agrees with a theory called “feature matching”, which proposes that instead we memorize a (much smaller) set of features that describe the letter’s shape. This means we identify a letter by determining what its visual features are: lines, curves, intersections, etc., and comparing those features to lists in our memory. For example, when you read this letter ‘A’, visual processes in your brain determine that it is composed of two diagonal lines that meet in an L-intersection, a horizontal line that intersects them in two T-intersections, etc. The idea that our brains respond to such basic features is iwell-supported by scientific research (and arguably goes back to the cat experiments of Hubel & Weisel— check that out below!).

[youtube https://www.youtube.com/watch?v=IOHayh06LJ4?rel=0&w=560&h=315]

The upshot of feature matching is that a lot of the variability we see in fonts, size, etc., don’t matter—think of all of the ‘A’s in that figure that have in common those two diagonal lines and a horizontal line. Of course, some shapes that we consider to be the letter ‘A’ look quite different, and so it must be the case that we memorize a separate set of features to identify those ones—most obviously, the lowercase ‘a’ has very different features than the uppercase ‘A’ (two different shapes that share the same letter identity are called “allographs”; look out for Part 2 of this blog entry for more on that topic!).

The downside of feature matching is that it is not obvious what the features we actually use are—and so researchers remained challenged with determining this. One thing we do know is that expert readers, like you as you read this blog, pay attention to different features than do people who don’t have expertise (e.g., children, or second-language learners; see references). The most likely reason for this might be that experts have a better sense of what is or isn’t important—and when it comes to reading, what is most important is distinguishing between different letters. This means we become better are ignoring irrelevant features that don’t change the letter’s identity (think about some of the ‘A’s in the figure that have a lot of extra flourishes—you know that they’re not important, but someone just learning to read might not!).

Suggested reading: Hofstadter, D. (1995). On seeing A’s and As. Stanford Humanities Review, 4(2), 109–121. https://web.stanford.edu/group/SHR/4-2/text/hofstadter.html

References:
Wiley, R. W., Wilson, C., & Rapp, B. (2016). The Effects of Alphabet and Expertise on Letter Perception. Journal of Experimental Psychology: Human Perception and Performance, 42(8), 1186–1203. https://doi.org/10.1037/xhp0000213

Palmer, S. E. (1999). Vision science: Photons to phenomenology (Vol. 1). Cambridge, MA: MIT Press.

Gibson, E. J. (1969). Principles of perceptual learning and development. East Norwalk, CT: Appleton-Century-Crofts.

Fiset, D., Blais, C., Ethier-Majcher, C., Arguin, M., Bub, D. N., & Gosselin, F. (2008). Features for uppercase and lowercase letter identification. Psychol. Sci.

Courrieu, P., Farioli, F., & Grainger, J. (2004). Inverse discrimination time as a perceptual distance for alphabetic characters. Visual Cognition, 11(7), 901–919.