Thinking About Prototyping - Paper Prototyping: The Fast and Easy Way to Define and Refine User Interfaces - page 51

The fascinating thing about this disagreement was that neither developer was saying a word about their
unspoken assumptions, they were simply battering each other with their conclusions. Once I started
asking them why they held their position, then the assumptions came out. Now we had some tangible
questions to research: How often did records get overwritten in the current system? How likely were
delays in bringing up the form for editing? Did the slowness of the system cause trouble for the CSRs?
(Unfortunately, none of these questions got answered because the company was bought and the entire
development team was laid off 2 days later.)
Strictly speaking, any kind of usability testing gives you a way to discover whether your assumptions
about the design are true or false. Paper prototypes let you get this information early, before you've
invested effort in coding. When a question arises, the team can say, "We're testing the prototype next
week, so we can ask some users." Then it magically becomes an issue for research, not argument.
[ 1 ] Like the children's topic character Amelia Bedelia, we sometimes misinterpret what our customers
are asking for. (From Thank You, Amelia Bedelia by Peggy Parish. New York: HarperTrophy, 1995.
Reprinted by permission.)