What Are Disabilities?

Individuals are not disabled; rather, some people have difficulties performing certain tasks, such as using a mouse or reading small print. When these limitations are serious enough to impact the person’s performance, they are referred to as “disabilities.” Anyone can experience the same difficulties because of illness, accident, environment (such as loud background noise), or hardware error (such as a missing mouse).

Disabilities can be classified into the following general categories:

• Visual impairment. This ranges from slightly reduced visual acuity to total blindness. Those with reduced visual acuity might only need images to be reasonably sized or specially enlarged, or they might need high contrast between foreground and background. Users with more severe impairments might require that output be translated into audible cues, spoken text, or Braille.
  
  
• Hearing impairment. Some individuals do not hear beeps, distinguish different sounds, or recognize spoken words. These users might need the computer to prompt them in a different manner, such as a screen flash, an indicator lamp, or an on-screen message.
  
  
• Movement impairment. Some users are unable to perform certain manual tasks, such as using a mouse or typing two keys at the same time. Others might have a tendency to hit multiple keys, might “bounce” fingers off keys, or might be unable to hold a printed book. Many users need keyboards and mouse functions adapted to their requirements, or they may rely exclusively on a single input device.
  
  
• Cognitive impairment. Cognitive impairments take many forms, including memory loss, perceptual differences, and conditions such as Downs syndrome. Language impairments such as dyslexia or illiteracy are also very common. Those who speak English as a second language can be considered to have a form of language impairment. Proper design can increase accessibility for these computer users.
  
  
• Seizure disorders. People with some forms of epilepsy might experience minor or severe seizures when a monitor flashes at certain rates or they hear certain types of random or repetitive sounds.
  
  
• Speech impairments. Although speech difficulties do not normally affect a person’s ability to use a computer, it can be a problem in using telecommunications and voice menus. And in the future, speech difficulties might affect normal computer usage if voice recognition becomes a common form of input.