Surprisingly, another extremely important contribution of personas is their value as a communications tool. The cast of characters becomes a design taxonomy with great power to explain our design decisions. Even more, they become a spotlight, showing the programmers, marketers, and managers that our design decisions are obviously correct.
It is vitally important that everyone on the design team not only become familiar with the cast of characters, but that each persona become like a real person—like a fellow member of the development team. Programmers—with their mathematical nature—have a natural reluctance to think about specific user cases, preferring instead to think about general cases. This spills over into their thinking about users, and they are always imagining users in the aggregate, the average, or the generic. They much prefer to speak of “the user” than of Judy, Crandall, Luis, Estelle, Rajiv, and Fran.