The majority of typographic applications are aiming to ensure that complex human thought and speech can be effortlessly carried from one person to another by means of the written word, usually at smaller sizes, and with continuous copy. An important exception is UI design, where isolated words, often without much context, need to be unambiguously identified, defining one key accessibility requirement for the target audience and requiring designers to understand how we read.
Most people would say that we see with our eyes, but in fact we see with our brain. The eyes are merely the brain’s light measurement devices which use photoreceptor cells to convert photons into noisy and incomplete electrical signals that are carried over the optic nerve to the brain’s visual cortex. The visual cortex works with different parts of the brain to manufacture a convincing and consistent image of the world using facial recognition, object recognition, spatial orientation and many other functions. Our eyesight plays an important role in the quality of the image that the brain is able to create, but when it comes to typography it’s especially important to understand how the brain uses the movements of the eye to maximise information collection from the letters and words in a line of text.
When we read, the brain moves the eyes in saccadic rather than smooth movements. Both eyes are quickly and simultaneously moved from point to point and each jump ends in a fixation during which about seven to nine characters are captured. At a normal reading distance of about 30 centimetres and a type size of 9pt to 11pt, the captured characters will usually fit within the fovea, the central area in our eyes where the daytime photoreceptor cells are most densely packed, so the brain sees sharpest. The visual information is converted to electric charges that travel along the optic nerve to the visual cortex. Irrespective of language and writing system, the decoding of letter shapes occurs in the visual word form area using its connections to the visual cortex and language centres. Despite the brain having an area dedicated to visual language, the decoding of letter shapes is an acquired skill and has to be practised to remain proficient. It is here where we can see why ambiguity between letter shapes dramatically reduces the brain’s ability to quickly and correctly decode individual letters, and to form them into word shapes.
Word shapes are given meaning in the lexical semantic area but, depending on shape and features of the language, it is not always possible to successfully access the meaning from shape alone. Here the phonological area of the brain supplements the word shape with a sound shape, and using both together, meaning can be attributed. The process of reading, from capturing a saccade to decoding, is repeated again and again until the brain can make sense of what it sees.
Accessibility can be affected at any point in the process from when the fovea is stimulated to the brain establishing the meaning of a word. Best typographic practice can support this process and alleviate many accessibility problems simply by being mindful of the audience.
The visual acuity of a 55-year-old is only 20% of that of a 20-year-old, meaning that very small sizes of text are very hard to see for an older person. This effect is exacerbated when there is little contrast between foreground and background colour. For UI and continuous copy at normal reading distances, the optimal size is around 10pt or 11pt. Larger sizes may be seen better by groups of people with specific visual impairments but are detrimental to fluent reading by the majority of the population.
The choice of typeface and letter spacing also play important roles. The higher the potential for mistaking one letter shape with another, for example in typefaces like Helvetica or Arial, the greater the ambiguity. Varying and differing width proportions, and open letter forms contribute to reduce ambiguity, increasing accessibility. Tight letter spacing should be avoided as it creates visual crowding, impairing recognition, while very tightly spaced letter pairs can easily be mistaken for a single character.
High-contrast typefaces in the style of Bodoni should be avoided at small sizes and in continuous reading as they create a visual striping effect. This has a photostrobic effect on the brain, making it highly detrimental to accessibility, and in rare cases can trigger an epileptic seizure. Using a-low contrast typeface provides broader accessibility.
In summary, it’s important to remember that conventional and established typographic rules have their roots in historical development and experience; what typographers have long known to be true through observation, today can be proved using neuroscientific methodology. Understanding your target audience and applying skill, best practice, and sensitivity will ensure that typography contributes to the success of a design without compromising the aesthetic qualities of a modern age.
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