Humans posses many abilities for interacting. Sometimes these abilities are reduced through environmental factors, injury, disability, or natural degradation from aging. The key to accessing electronic devices is to use the other abilities that we have when the preferred abilities are not available to us:
Seeing enables us to use visual interfaces such as computer screens, VCR programming etc., and to be able to locate buttons. For example, being able to tell if a number pad has the “1” key in the top left or bottom left.
An inability to see anything on an electronic device might come from it being dark, from our eyes being occupied elsewhere (e.g. while driving a car), or from disease or injury which causes blindness. Alternative means of interacting in this case include speech input and output, using lists of interface elements (instead of having to feel around for them), and tactile displays such as Braille.
A difficulty in seeing electronic devices might result from it being too dark, from us leaving our glasses behind, from having color vision deficiencies, or from disease or injury, which can create a very wide range of visual abilities (from losing half our vision, to having patchy or blurred vision, to having tunnel vision etc.). Alternative means of interacting in this case include those for an inability to see (speech input and output, using lists, and tactile displays) as well as changing the way something looks (enlarging text, changing colors or font types etc.).
Hearing enables us to hold spoken conversations, for example to be able to converse with another person on the telephone, to listen to music, to watch TV, to hear devices which beep to tell us when something is finished (like microwave ovens).
An inability to hear the sounds coming from an electronic device might be from working in a noisy office or shop-floor, from being in a noisy bar, or from disease or injury which causes total hearing loss. Alternative means of interacting in this case include showing visual events for audible events (e.g. a flashing light as well as a beep), giving written text and annotation for spoken text and incidental sounds (e.g. closed captioning).
A difficulty to hear the sounds coming from an electronic device might come from being in a moderately noisy environment, or in a necessarily quiet environment (e.g. a library), or from disease or injury which causes decreased hearing (e.g. conductive hearing loss), or interrupted hearing (e.g. tinitus – a constant ringing sound in the ears). Alternative means of interacting in this case include those for an inability to hear (visual events for audible events), and changing the way something sounds (for example making it louder, changing the pitch), or connecting it directly to a hearing aid.
Speaking enables us to hold face-to-face or over the telephone conversations, to give speech input (for example to place a collect call using a computerized operator).
A difficulty or inability to speak (and be understood clearly by the listener) might come from being in a noisy bar, or from being in a quiet library, from just returning from dental surgery, from having a strong accent or dialect, or from disease or injury which prevents the mouth functioning in the normal way. Alternative means of interacting with electronic devices in this case include using a keyboard or keypad to enter information instead of or in conjunction with speech input.
Being able to touch and manipulate items with our hands enables us to press buttons, to move switches and dials, to make gestures etc.
An inability to touch and manipulate might come from being too far away (e.g. too high or too far to reach, like a small child at a vending machine), or from disease or injury which causes an inability to reach (e.g. paralysis below the neck). Alternative means of interacting in this case include using remote-control devices, and using speech input.
A difficulty in touching might come from having gloves on in cold weather, or from disease (e.g. cerebral palsy which might make hand-control difficult) or injury (e.g. having a big bandage on one’s hand).
Alternative means of making input in this case include those for an inability to touch (remote control, speech input) and being able to confirm selections (e.g. giving speech or highlighting feedback, and then requiring confirmation of that selection using another button that is separate and distinct.
Our ability to understand something is determined by the skills and knowledge we posses to interpret and process what we experience. The ability to understand can be reduced by such factors as load (e.g. how many tasks we are doing at one time), stress (e.g. if we are panicking, or under time-pressure), or from fatigue (e.g. being awake too long or expending too much mental effort). It can also be caused by confusion when something is not communicated at our level (e.g. an engineer might understand a term, which a layman does not; a physician might understand a medical term, which an engineer does not).
Reduced ability to understand can also come from disease or injury which affects mental processes. Alternative means of interacting in this case include changing the way something looks (e.g. colors, text sizes and fonts), changing the level of the language (e.g. simplification), changing the way speech is presented (e.g. making it faster or slower etc.), and using a remote control which simplifies the interface.
Our ability to understand each other comes from having a common language. However, when we move to a foreign country, for a short period (vacation or a business trip), or a long period, we may be unable to understand, or at least have some difficulty in understanding the local language.
Combinations of different needs
In addition, people might have combinations of reduced abilities, for example not being able to see and hear well. These combinations of reduced abilities require us to use our other abilities in sometimes unusual or innovative ways. There may be a need to use a combination of the strategies above, or even different strategies altogether.
The need for general good design
Note that the alternative means of interacting with electronic devices described here can be augmented by good design: as an example, speech input might be an alternative when something is too far to reach, but if moving the interface elements to within easy reach of everyone is possible, then that is a far better and more universally acceptable solution.
Basic rules to be applied when speaking or relating to a disabled persons. These mostly imply a basic understanding of the relevant impairment and a minimum of politeness on the part of the non-disabled person.