Usability vs Intellectual Disability

Focus on the fundamentals of usability

Hi! After having spied around on Medium for a year or so, I’m going to do my first attempt at writing an article. It’s also my first public attempt to write a serious one (and even the first one in English), so, hold on tight!

The last few months we’ve been working on a prototype for a mobile application that helps people with an intellectual disability to travel individually by public transport to e.g. their school or workplace.

Our target group had a mild to moderate intellectual disability, and we focussed primarily on the intellectual limitations, not at physical limitations. These people can (to some extent) interact independently with computers and smartphones.

An important thing for people with an intellectual disability is to look at the extend to which an individual is able to perform tasks independently, as so with traveling by public transport.

The intrinsic motivation of this user group is often very high. Because of that, really a lot of people in this user group are willing to and — with a little bit of help — capable of traveling individually by public transport. By creating applications like these, people are less dependent of others and it saves them money by not having to travel by specialised transport.

The problems

There are a few problems that are currently preventing these people from using public transport. What happens when something changes, for example when the train is delayed or cancelled? What if they take the wrong bus or forget to leave the bus at the right stop? Panic!

Another obstacle are vision problems. A part of the users have vision problems and will thereby have difficulties reading departure times, line-numbers, platform numbers and so on.. Also, due to cognitive disorders, it will be hard for them to remember the complete route and possible alternatives from starting point to their destination (not to mention finding a solution in case of failure).

As you can see, there are a lot of issues to take in account, which makes good guidance and support provided by our application very important.


The hard part when designing applications for this user group is that there is no typical behaviour or needs related to an intellectual disability. Not everyone has the same limitations, requirements and cognitive skills, which makes it hard to adapt.

One of the most important parts of usability is to allow the user to complete a task correctly, while keeping the frustration to a minimum.

The point at which ambiguities arise and real frustration kicks in is much higher for us than for people with an intellectual disability. Where people without an intellectual disability would simply ‘skip’ this point (while not even consciously noticing it), people with an intellectual disability will be struggling, which may block them from using your product.

The amount of frustration a user can handle before ‘real frustration’ kicks in

This means that optimising the usability is particularly important for this user group. By removing blockages, you will allow people with an intellectual disability to use your product with less (or even better: no) confusion and frustration.

Besides that, optimising the usability of your products with an intellectual disability in mind is not only essential for this user group. Optimising in this way can be important for everyone using your product, even if they don’t have any limitations. The fact that people without an intellectual disability will simply ‘skip’ this frustration point, doesn’t mean they completely ignore it. There is still a bit of frustration in their mind, so by optimising this, you will also improve the quality for them, whether they actually notice it or not.

How can we do it better?

Below are a few points which turned out to be pretty useful and important when designing for this user group:

1) Situated Cognitive Engineering (sCE)

Situated Cognitive Engineering is a very good method when doing your design process. This method was originally created for a space program where they needed guidelines on designing human-centered interactive multimedia interfaces.

There is a clear need for a concise and coherent design approach for the space domain that guarantees usability of the in-orbit user interfaces.
(NASA Appendix H, 1998)

This method proved to be a very solid way to use in the research and development of our product, because it puts the user in the front seat. Instead of starting to think from your knowledge, you start looking at what and how the user really needs it.

2) Test, test, test..

One of the most important tips is to test! And a lot of it! Things that initially seem obvious to you may prove completely illogical after testing it. You can try to empathise with your target group as much as you would like, but in reality you will always run into unexpected cases.

Besides testing with users in your user group, you can also test and evaluate your prototype with experts in the field. For example, a thing we learned by talking to some experts was that a lot of the users are missing a sense of time. How long is ‘one hour’? How long does it take until the afternoon? This seems very hard to understand and it was something we would’ve never discovered without performing tests or talking to experts.

3) Logical consistency

Think about the navigation and the way you present your information. It’s not primarily about ‘the amount of clicks to get to the right information.’ What’s more important is the logic and consistency in which you are offering the information and handling the navigation flow.

A thing to keep in mind is that these users often have a lack of memory skills, so providing your content in a logical and consistent way can help them a lot in reaching the right content.

4) Be clear, without distractions

Focus on what’s important and think a lot about what’s really necessary. Be crude, get rid of everything that doesn’t necessarily has to be there.

It is also important to think about cognitive functions like the speed of reading and thinking, the overall intelligence, the performance of the memory, the concentration, and so on..

Besides the contextual parts, you can clear things up by choosing the right fonts (sans serif fonts work best ☺), the size of that fonts and the use of color contrasts.

Note: please don’t overreact when I say ‘color contrasts’. If you still decide to give me the finger on this one, no problem, but in that case be sure to give your users an option to enable or disable an optimised layout for the visually impaired and color blind people. For 95% of your users, it is way more important that your application looks good than it being fully optimised for vision problems.

5) Supportive functions

Besides providing logical consistency and having a clear interface, you can also help your users by giving them supportive functions like voice help.

Voice help can be important when people can’t read that well or when their speed of reading is very slow, but it can also remind them of things like “You’re almost at your destination, don’t forget to checkout!”, or “Your bus is delayed, it will arrive in 10 minutes.”


As Tim Berners-Lee (the W3C Director and inventor of the World Wide Web) once said:

“The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect”

I think it’s important to do what’s best to give people with an intellectual disability the possibility to participate in our information society with the greatest possible independence.

When designing applications, it is important to know the underlying design theory and use this as a foundation, but it is even more important to always put your users in the first place. With every step or decision: start with them, not with your theory.

Thanks for reading!