A quick opinion about personas, prompted by a question from a friend.
When choosing a picture for a persona, use a real photo, not a cartoon. A cartoon doesn’t add life to a persona; it drains life from it.
It’s easy to think that the deliverable itself is the persona. It’s not. Your deliverable should create a shared mental model among your team; that is the persona. Mention a persona by name and you don’t want people to remember the paper stuck on the wall. You want them to remember a lifelike person. Only then can the entire team have a stable, realistic reference point for design discussion.
A cartoon doesn’t create this realistic mental picture. Viewers have to fill the gaps between the drawing and the reality, and tend to fill it with something close at hand – an extension of themselves (see Understanding Comics), or a crude stereotype. Therefore a cartoony persona often creates a rubbery, clichéd representation of a person, easily bent into whatever shape is needed to use as false evidence.
That’s not to say cartoons are useless. I use them often in high-level sketches to represent users we don’t yet know enough about. I’ve also used them to extend an existing persona (see below), particularly when illustrating how a specific persona uses a product through a storyboard. The storyboard isn’t photorealistic, so it follows that the protagonist should be hand-drawn also. But I only use this shorthand once the team has grown to know and love a photorealistic persona; that is, once the mental model has been established.