Alan Cooper tells how he invented the use of personas as a practical interaction design tool:
"[...] Even though the variation among the users was dramatic, a clear pattern emerged after just a few interviews. The users fell into three distinct groups, clearly differentiated by their goals, tasks, and skill levels. [...] So I created Chuck, Cynthia, and Rob. These three were the first true, Goal-Directed, personas.
Chuck was an analyst who used ready-built templates and reports. Cynthia was an analyst, too, and she used similar ready-built templates. But Cynthia also wrote her own templates, which she gave to Chuck to use. Rob was the IT manager who supported both Rob and Cynthia. He could optimize Cynthia’s templates, but he would never originate or use them.
At the next group meeting, I presented my designs from the points of view of Chuck, Cynthia, and Rob instead of from my own. The results were dramatic. While there was still resistance to this unfamiliar method, the programmers could clearly see the sense in my designs because they could identify with these hypothetical archetypes. From then on, I always presented design work using one of the personas, and eventually even the Sagent engineers began to talk about “what Cynthia would do” or “whether Chuck could understand” some dialog box."