3. Verify your product's acceptability to users

As soon as you have the first mock-ups of your product, test them. Some designers use "disability simulators" for this purpose, such as software that allows you to adopt the point of view of a user with impaired vision or hearing, or gloves specially designed to simulate a dexterity problem. However, the best thing to do is to test the product (or mock-up) with real users! If you don't have direct contact with them, you can go through associations, which will be invaluable in meeting your users and organizing user tests (location, protocol, logistics, etc.).

The aim of these user tests should be to characterize the acceptability of your product. This is based on three criteria:

• Functional acceptability: this notion relates to product ergonomics and is independent of the product's technical performance. It breaks...