[Note: this page looks at disability and product design through several animations. Use the text links and click “Show Me” to view the animations; the thumbnail images contain alternate text for the animations.]
Looking at disability through the lens of product design, it can be argued that there is no disability until there is an inaccessible product. Disability can be defined as the gap between what a product demands of the user, and what the user is able to provide.
All products make demands upon the user. These demands occur along several dimensions — let’s say there’s vision, hearing, dexterity, cognition, and speech. Products often make demands along more than one of these dimensions at a time.
Those performance requirements can be very demanding, or easy. Let’s say they can be quantified according to how many people in the total population can perform them with little or no difficulty. The easiest task would be ‘100%’ — everyone can do it. On the other hand, some tasks require so much that only 10% of the population can perform them.
Now, let’s think about the user. The average user is at 50% for all tasks — an average ability. In this sense, ‘disability’ means anything significantly lower than average, in one or more category of ability.
Let’s say there’s a person who is in the ‘normal’ range for all functions except hearing. How do the demands of the cell phone interact with her abilities?
So disability, to the extent that it means inaccessibility, results from the interaction between the product and the user. Lowering the requirements can increase the number of successful users.
For each individual there is a set of bell curves with points that indicate their abilities along the different dimensions.