Design with the Human Visual Acuity in Mind

Every designer has the intention of designing a product that succeeds in capturing attention. But not every product that hits the digital world becomes a success, one reason being, not many designs take the human anatomy limitations into consideration. One of the limitations and by far the most important one is vision as things need to fall into our line of sight before they can capture our interest. And, when I say sight, I mean the foveal vision and not peripheral where we can neither see colour nor read.

Fovea, is the only part of the eye retina that permits 100% visual acuity, which is necessary in humans for activities where visual detail is of primary importance, such as reading and driving.
The fovea covers the central 3 degrees of our sight — for most users set at a monitor, a circle of 2.5cm diameter on screen. Everything outside this point counts as peripheral vision, with sight cells becoming progressively sparser further away from the fovea.
The number of retina colour cells are also reduced moving from the fovea to the periphery and as a result, at the outer edges of our vision, we are completely colour-blind.
The fovea and periphery have also got different nerve cells. The X cells in fovea are more sensitive to sustained signals, hence better precision and the Y cells in the periphery are more responsive to rapid changes than sustained stimuli. As a result, peripheral vision is extremely motion sensitive.
Speed Reading and Foveal Vision
Speed reading is any of several techniques used to improve your ability to read quickly.
When you read, you look at a word or several words. This is called a fixation. You then move your eye to the next word or group of words. This is called a saccade. After this is repeated once or twice, you pause to comprehend the phrase you just looked at. Speed readers claim that they reduce the fixation time on a word.
One method that digital speed reading tools and apps have been using recently is called Rapid Serial Visual Presentation (RSVP). Single words flash on the screen so you’re concentrating on a single word at a time. Once you get used to the system, you can increase the speed the display shows you words.
In RSVP speed reading method, the human anatomy, the foveal acuity in particular, has been an important design factor. By eliminating the time you normally spend on moving your gaze from one spot to another in order to put the words in your foveal vision and make them readable, the speed of your reading increases.

BUT…..the human anatomy is a complex system, if something resonates with one part of it, it doesn’t mean that it resonates with the system.
The human working memory can only hold about seven digits at a time, or six letters, or four-five words, or a single addition problem.
With RSVP apps, it is our working memory that is put to test as well as the foveal acuity. When the words appear on the screen fast, we may be able to read them faster than the conventional reading but working memory gets overloaded and words come in faster than you can deal with them. Studies show, that is how your comprehension drops. you’re not taking in the information, which defeats the purpose of reading.
Of course the RSVP speed reading apps are still great tools for reading news, emails, messages and any other topics that do not require complete comprehension and mental effort.
Where else can RSVP feature be used?
The RSVP system can be potentially utilised well in many other applications such as the following:
Fitbit notifications
Fitbit, the wearable activity tracker, can receive notifications from your iOS or Android mobile device in most models. Due to the screen size limitations, Fitbit scrolls your notifications on the screen. This creates a movement of words from one side of the screen to another, just like a news ticker.
As covered above, the X cells that are concentrated in our Fovea, are more sensitive to sustained signals as opposed to the Y cells in the periphery that are more responsive to rapid changes. Therefore, since the Fitbit screen is small enough to fit in our foveal vision, scientifically, it is better to eliminate the movements of the words and instead, use the RSVP method by showing the notifications one word after another. This way, you can read the notification faster with less effort. As the human mind is a cognitive miser, anything that does the work with less effort required appeals to it.
Below, I have made some prototypes for Fitbit notifications based on the aforementioned theory. RSVP speeds in the three prototypes are 180, 240 & 360 words per minute (w/m) respectively.
Video Subtitles
I am a foreign film and TV show fan. SBS on demand (in Australia) is my best friend these days as I like the European TV shows with rich storylines. However, reading subtitles drains your energy, especially on a weeknight after a long day at work. On top of that, reading subtitles keeps you from observing the entire frame while watching films as the subtitles are normally in 1 or two lines at the bottom of the screen where there is close to nothing to obstruct.
When you point your foveal vision towards the subtitle, everything else on the screen moves to your peripheral vision and you miss out on complete observation. But what if the subtitle is not right at the bottom of the screen and it is further up instead and possibly near the person who is speaking?
There is also another problem that you are facing, if you are not a fast reader, the frames will change before you read the whole 1–2 lines of words. This is where RSVP speed reading method could possibly assist.
Below is an early stage prototype that I have made of the above idea. RSVP speed, 360 w/m.
While my subtitle prototype is still immature, I still think the idea is worth exploring. What do you think?
