Foundations of Disability, Accessibility, and Inclusive Design
Models of disability
The medical model locates disability in the person and treats it as a defect to be fixed. The social model separates impairment (a condition of body or mind) from disability (the barriers society erects). Modern law and practice - the ADA, the UN CRPD - blend them into a biopsychosocial / ICF view: disability emerges from the interaction between a person and their environment. Exam items love the trap of describing a barrier as the user's problem ("the screen reader user could not find the menu") rather than a design failure ("the page had no headings or landmark structure").
Categories and context
Expect questions on vision, hearing, motor/dexterity, speech, cognitive (memory, attention, learning), neurological, and chronic health or mental health conditions. Remember that disability is frequently invisible, acquired later in life, and fluctuating. The classic trio - permanent, temporary, situational (a broken wrist, a noisy train, bright sunlight) - shows why a solution built for one group helps many: the curb-cut effect.
Related terms
- Accessibility: the outcome - people with disabilities can perceive, operate, understand, and robustly use the product.
- Universal design (Ron Mace; seven principles): usable by all, without adaptation.
- Inclusive design: a process that deliberately includes excluded groups; broader than disability alone.
- Usability is not accessibility: an interface can be efficient for most people and unusable for some.
Traps: "accessibility only serves a tiny minority" (roughly one in four U.S. adults reports a disability); "accommodations are separate from design"; treating inclusive design as a visual style.
Rule of thumb
Design for the edges and the middle benefits. If it works for a keyboard-only, low-vision, screen-reader user, it is almost always better for everyone.