Something to Think About...

computer generated image of a human headThe concept of cognitive disabilities is extremely broad, and not always well-defined. In loose terms, a person with a cognitive disability has greater difficulty with one or more types of mental tasks than the average person. There are too many types of cognitive disabilities to list here, but we will cover some of the major categories. Most cognitive disabilities have some sort of basis in the biology or physiology of the individual. The connection between a person's biology and mental processes is most obvious in the case of traumatic brain injury and genetic disorders, but even the more subtle cognitive disabilities often have a basis in the structure or chemistry of the brain.

A person with profound cognitive disabilities will need assistance with nearly every aspect of daily living. Someone with a minor learning disability may be able to function adequately despite the disability, perhaps even to the extent that the disability is never discovered or diagnosed. Admittedly, the wide variance among the mental capabilities of those with cognitive disabilities complicates matters somewhat. In fact, one may reasonably argue that a great deal of web content cannot be made accessible to individuals with profound cognitive disabilities, no matter how hard the developer tries. Some content will always be too complex for certain audiences. This is unavoidable. Nevertheless, there are still some things that designers can do to increase the accessibility of web content to people with less severe cognitive disabilities.

Functional vs. Clinical Cognitive Disabilities

There are at least two ways to classify cognitive disabilities: by functional disability or by clinical disability. Clinical diagnoses of cognitive disabilities include autism, Down Syndrome, traumatic brain injury (TBI), and even dementia. Less severe cognitive conditions include attention deficit disorder (ADD), dyslexia (difficulty reading), dyscalculia (difficulty with math), and learning disabilities in general. Clinical diagnoses may be useful from a medical perspective for treatment, but for the purposes of web accessibility, classifying cognitive disabilities by functional disability is more useful. Functional disabilities ignore the medical or behavioral causes of the disability and instead focus on the resulting abilities and challenges. Some of the main categories of functional cognitive disabilities include deficits or difficulties with:

  1. Memory
  2. Problem-solving
  3. Attention
  4. Reading, linguistic, and verbal comprehension
  5. Math comprehension
  6. Visual comprehension

The main reason why these functional disabilities are more useful when considering web accessibility is that they are more directly related to the concerns of web developers. Telling a developer that some people have autism is not very meaningful unless the developer knows what kinds of barriers a person with autism might face on his or her web site. On the other hand, telling a developer that some people have difficulties comprehending math provides the developer with a framework for addressing the needs of this type of audience.

Additionally, clinical diagnoses are not mutually exclusive in terms of what difficulties the people face. There is often considerable overlap of functional disabilities within clinical diagnoses. A person with memory deficits may also have difficulty with attention or problem-solving, for example. This kind of overlap fits within a medical model, but is not particularly helpful to web developers, who simply need to know what the person can or cannot do.


Memory refers to the ability of a user to recall what they have learned over time. A common model for explaining memory involves the concepts of working (i.e., immediate) memory, short-term memory, and long-term memory. Some individuals with cognitive disabilities have difficulties with one, two, or all three of these memory types. Some users may have memory difficulties that impair their ability to remember how they got to content. Consider a complex form that displays multiple error messages at the top of the form when submitted. It may be very difficult for the user to remember multiple errors, or perhaps may even forget the error information before they are even able to address that error.


Some individuals with cognitive disabilities have a difficult time solving problems as they arise. In many instances, their resilience can be low and the resulting frustration is such that they choose to leave the site and not persist to solve the problem. One example of this would be the presence of a 404 error from a bad link, or a link that does not take them where they thought they were going.


A distracted studentThere are many individuals that have difficulty with focusing their attention to the task at hand. Distractions such as scrolling text, blinking icons, and pop-up windows can make the web environment difficult or even impossible. Even for typical users, such things can be irritating. Good design principles would limit these instances to only that which is necessary to convey the content.

Some people with Attention Deficit Hyperactivity Disorder (ADHD) have difficulties learning, but oftentimes this is due to their distractibility, rather than to any kind of inability to process information. People with ADHD can be impulsive, easily distracted, and inattentive. On a positive note, some people with attention deficits are highly creative and very productive in short bursts, with an abundance of energy and enthusiasm. On a less positive note, it can be difficult for people with ADHD to stick to a task for a long period of time.

Avoiding anything that draws a person's attention away from the main content and using good design, such as color, white space, and simple presentation can help users focus on important content and functionality.

Reading, Linguistic, and Verbal Comprehension

complex words floating through spaceSome individuals have difficulties understanding text. These difficulties may be mild or severe, ranging from minor challenges to a complete inability to read any text. It would be unreasonable to expect web developers to accommodate the entire range of reading abilities. The difference between non-readers and genius readers is simply too vast. It is reasonable, however, to expect developers to write as simply and clearly as is feasible, taking into account the primary audience and including those who may have difficulty with some of the content. After all, an estimated 15-20% of the population, including many of the brightest minds of recent generations such as Albert Einstein, Thomas Edison, and Henry Ford, has some sort of language or text comprehension difficulty.


Here is one example of a reading problem. Note that it may be one of perception or of processing. See if the associated accessibility fix helps you.

What is being said in this phrase?

Tob eornot obe

Now check the power and importance of embedded graphics as a way to enhance the context of the written word by looking at the phrase with a graphic.

Non-Literal Text

Non-literal text, such as sarcasm, satire, parody, allegory, metaphor, slang, and colloquialisms, can be a problem for some readers. In some cases, readers will not realize that the words are not meant to be understood literally. A writer who says "I just love getting stuck in traffic when I'm already late for work" probably means the opposite of what this sentence actually says. Sarcasm such as this can be confusing to some readers. Similarly, someone who reads she must "get her ducks in a row" may not realize that the author is probably not referring to real ducks at all. The author is suggesting that the reader get organized or disciplined, using the comparison of a mother duck with her ducklings lined up behind her in order to illustrate the concept.

Non-Existent Text

The unstated assumptions and implied meaning of written content may seem obvious to the writer, but readers may not have the necessary background knowledge. Some readers may not have the skills to infer meaning from text without additional help.

Math Comprehension

Mathematical expressions are not easy for everybody to understand. This does not mean that authors should avoid math entirely. For people who are comfortable reading equations and thinking mathematically, the best way to explain mathematical concepts is to use equations. On the other hand, often it is helpful to explain math conceptually, either with or without the formulas. Conceptual explanations help readers understand the reasoning behind the math.

Visual Comprehension

Some individuals have difficulties processing visual information. In many ways, this is the opposite of the problem experienced by people with reading and verbal processing difficulties. Individuals with visual comprehension difficulties may not recognize objects for what they are. They may recognize the fact that there are objects on a web page, but may not be able to identify the objects. For example, they may not realize that a photograph of a person is a representation of a person, though they can plainly see the photograph itself (as an object) on the web page.

For these people, a moving, talking person in a video may be easier to identify and mentally process than a static image of a person in a photograph. Video and multimedia, accompanied with narration, may be the best way to communicate to these individuals.