One consequence of human evolutionary history is that we are profoundly social creatures. Ancestral hominids lived in each others' pockets, traveling in small nomadic bands that stuck close together for mutual protection. Through most of our evolutionary history, among the most important of our adaptive challenges has been getting better at the games of communication and contract that determined success within the social group — because thus conditioned the amount of protection won got, and one's degree of access to the best food and the choicest mates.
Thus, human beings have developed elaborate machinery for modeling each others' mental states. A significant portion of our brains is devoted just to recognizing and interpreting facial expressions. We are hardwired for negotiation in more subtle ways as well; evolutionary psychologists have found that hunan beings do substantially better on logic problems when they are framed as a way to spot people who are reneging on agreements.
So powerful is our instinct to negotiate that we routinely project human consciousness onto the inanimate world in order to feel more comfortable with it. Primitives anthromorphize rocks and trees, the more allegedly sophisticated build cathedrals, and computer programmers often talk of their tools as if they were little homunculi even though they know exactly how mechanical the internals of the hardware and software are. It is human nature to see human nature everywhere, and to create it where it didn't previously exist to any extent that is possible. Indeed, some animal ethologists are beginning to think our demand for humanlikeness is so powerful that it occasionally elicits sentience in pets and domesticated animals that wouldn't have it in the wild.
We invent imaginary friends, and we tell stories about them. In his provocative and seminal work The Origin of Consciousness in the Breakdown of the Bicameral Mind (1976) pyschologist Julian Jaynes argued that the single most important characteristic that distinguished full human consciousness from that of earlier hominids may have been the development of a drive to narratize — to assemble out of the incidents of the world stories that have a beginning, internal causal connections, an end, and a meaning.
It would be surprising if pervasive behavioral biases towards negotiation and narratization didn't have implications for UI design. To date, attempts to make computer interfaces humanlike and social have been largely unsuccessful; human brains, honed by several million years of competition, too easily detect the shallowness of the simulations. Nevertheless there is a way we can use the phenomenon of projection to improve UI design. It called “ persona-based design”, and has been effectively championed in (among other places) [Cooper].
It is difficult and frustrating to design a UI for “the user” as an abstraction or impersonal statistical profile. But when we give the user a face and a name, even a fictional face and name, all our evolved machinery for modeling other minds, negotiation, and narratization gets engaged. UI design becomes easier, and can even yield some of the emotional satisfactions that we get from socializing with real humans or reading a book about fictional ones.
The steps in persona-based design are very simple:
First, invent some fictional users. You don't need a cast of thousands for this job, that many would be hard to track mentally. The number should be more than one; you want them to spread their traits across your target user population, and focusing on one single persona tends to prevent that. The number should probably not be more than four.
Make up the basics for each user — name, sex. age, personality traits, and a back-story about why they are using your software. Inventing your character's appearance is actually significant; you're going to have mental conversations with these imaginary friends, and that's easier to do if you can visualize them.
If you do this part properly, you will find that the persona takes on a life of its own and even disagrees with you. Do not be afraid of this or dismiss it as silliness; it is actually a sign of success, and means that your evolved machinery for modeling other minds is fully engaged.
Here is an example of what can happen when persona invention works exceptionally well:
In 2001, one of the authors (Raymond) once invented three personas for a public discussion of a GUI for configuring Linux kernels. One, representing the nontechnical end user, was Aunt Tillie: an elderly, kindhearted, somewhat scatterbrained woman who mainly uses her PC for email and web-surfing. The second, representing what we've called a power user or (in some areas) a wizard, was her nephew Melvin: a bright but socially challenged Linux geek who troubleshoots Tillie's problems. The third, representing what we've called a domain expert, was Penelope: a genetics grad student trying to squeeze more performance out of her chromatography gear and maybe find a boyfriend.
These characters came to life so vigorously that one of the participants in the discussion offered to date Penelope, and another one set up a website for Aunt Tillie! The trio (especially Aunt Tillie) subsequently showed up in discussions of UI design on other projects; various people wrote speculations about them, and they become minor but persistent mythic figures in the wider Linux community. (Aunt Tillie subsequently made a cameo appearance in [TAOUP].)
Having invented your personas, you now have to use them to develop your UI design. You can do this in two ways: private dialogues and public storytelling.
In private dialogue, you simply ask your personas how they would cope with the interface elements and metaphors you are composing. In public storytelling, you speak or write a little narrative about the persona's actions and reactions and share it with the rest of your development group (this method fits well into email channels). The narrative may lead to extended discussion or even argument about the persona's reactions and how to address them; that is
The point, in both cases, is to replace abstract questions about how the generic user would react with emotionally meaningful narratives about how a representative individual person would react, While this is no substitute for testing with users who aren't fictional, it is excellent preparation for that process and can forestall a surprisingly large percentage of the mistakes one might otherwise make.[29]
By building on our instinctive drives to negotiate and narratize, designing with personas helps us enlist for creative UI design not just the late-evolved and minor subsystem of logical consciousness but the entirety of our thinking and feeling brains.
[29] Persona-based design is not limited to being suitable for UIs. Developers practicing XP and other schools of agile programming have evolved a similar technique of designing by user story that appears to be one of the most effective tools in their arsenal.