Many products are designed for the majority, assuming that everyone else can adapt to the extent that their abilities allow. However, those with a different neurology often cannot adapt.
Much of my typological skills are based upon the research Colin Whieldon did for the Newspaper Advertising Bureau of Australia Ltd. Up until then, most layouts were based upon rules-of-thumb. The criteria he used to measure effectiveness of various typographical element was how much choices affected comprehension. For example, he showed that serif fonts and justified text were overwhelmingly better for comprehension.
Unfortunately, early computer graphical technology was not up to the rendering demands of either of these, so the early web relied upon sans-serif and ragged right and that has continued to this day. Unfortunately, no one since Colin has conducted the same type of research but focused upon computer technology, though being based upon light-emitive technology should not change the basic perceptional characteristics that print technology showed as most advantageous, but that is not the topic of this article.
What is interesting about Colin's research is that for some people better results occurred when using layout choices that countered what the majority preferred. Colin did not discuss this, but we know that those with certain neurological traits like autism have difficulty reading fully justified text, seeing it as the words being too far apart to hang together visually. So while most readers find justified text more appealing – books and Kindles still use justified by default – there is a distinct minority that have their reading severely disturbed by it.
Those with autism have other preferences that are distinct from most, like preferences for less bright backgrounds and larger line spacings. Unfortunately, rather than see that there are distinct sets of preferences between groups, an assumption has been made that so-called normal people can adapt to the preferences of this minority, leading to many sites that make the special adaptations for them standard, which is not a good thing to do, as it is like making everyone use long ramps instead of the quicker stairs.
In a way this thinking is a reverse of the past where the majority preference ruled and everyone else just has to adapt, like left-handed people having to use their right hands for scissors. Now the majority are expected to adapt to the needs of the minority, as WCAG wants to enforce, perhaps under the mistaken idea that so-called able-bodied people are more capable of adapting. This is bad thinking, as it is clear that people with different neurologies have distinct preferences that cannot be applied universally.
In basing the product heavily upon Colin's research, but knowing what someone with autism perceives from close experience, I chose to implement the previous WCAG advice and provide alternative renderings via a simple checkbox at the top of each page, with the setting persevering throughout a session through the links including it. It is still a compromise, as making it any more complex would likely dissuade visitors from proceeding.
Those with ADHD seem to have a distinct preference for more out-there designs compared to those with autism who prefer more subdued designs. Since the product is biased towards the more conservative design sensibilities that accompany the written word, I decided that the alternative renderings would be biased towards helping those with autism. While it can be used for more visually stimulating designs, one of the many drag-and-drop page design products might be better suited for them.
In designing a product, design decisions are not always simply about what the majority prefer, but then there are decisions about which groups to cater for, and how easy is it to do so, let alone what is the best way for users to make the choice. It is a balance between choice and how much distraction that choice requires. I chose a binary choice because it allows a simple checkbox to be used, providing as little distraction as possible while allowing significant enough differences in layout to make it worthwhile for readers to choose.
The default is still for the majority, as it should be, but a site owner can choose to set the site for the alternative as the default if it better suits the majority of their audience. Users given access to perform writing or administrative functions can set their own default.