1.10 Ensure compatibility with assistive technologies
The language that is used for things like operating instructions, button labels and displayed information should be clear, unambiguous and easily digested. It should not contain unnecessary jargon, colloquialisms, idiomatic expressions or convoluted grammar. Where possible, use explanatory icons, pictures or diagrams to aid understanding and provide for written text to be spoken for the benefit of users who have difficulty reading.
Many people find it difficult to understand complicated written text. Overall, 25% of the Irish population are "functionally illiterate", meaning that, while they can read to some degree, they would have difficulty reading a newspaper, filling in a form or following the instructions on a medicine bottle. Similarly, people whose first language is not English, such as first generation immigrants or foreign visitors, may have some reading ability but it may be low.
Literacy is also a problem for people who are deaf. A 1993 NRB survey found that 80% of deaf adults in Ireland had the reading age of an 8-9 year old. This is due to the difficulties of learning through sign language, which has a different grammar and structure to spoken or written language, or by lip reading.
There are various cognitive impairments, the best known being dyslexia, which also cause difficulty in reading complicated written text.
Keep it simple
The main technique is to keep it simple. Use everyday, jargon-free explanations. Avoid idiomatic expressions such as "on the one hand". Avoid long sentences by writing directly and concisely. You will often find that phrases like "on the one hand" are mere padding and can be removed without changing the meaning of the sentence. It is best if all instructions and information are written by experienced professional technical writers.
Supplement written instructions with audio
People who cannot read are often perfectly able to understand the same text if it is spoken. This can be achieved using either pre-recorded audio or speech synthesis. Speech synthesis, whilst more flexible, is often of much poorer quality and may be difficult to understand for some users and in noisy environments.
Supplement written instructions with pictures
Icons and diagrams can convey large amounts of information in an easily and quickly digested form. This may be the only medium that can be understood by people who are deaf and have poor literacy.
Allow user-selectable settings
Applying the previous techniques should result in a terminal which suits all users. However, in some cases, what is best for one group of users is not necessarily best for all. If this is the case, it may help if the user interface can be adapted by the user, or automatically for the user, to fit their individual capabilities. For example, some users may wish to choose spoken output, graphical buttons or fewer choices, whilst others may prefer to have only written text and more detail. The choice could be made by the user selecting from a number of displayed options. Alternatively, information required for the terminal to switch automatically could be encoded on a user's smart card at their request.
Test with real users
Try to ensure that all instructions and information are covered in the user tests which should include users who have low English literacy, preferably for a number of different reasons (education, nationality, hearing or cognitive impairment).
About user testing