People bring their baggage with them when they interact with the application that you’re designing. As they’re figuring out how your system works (because you know that few people read the manual), your users are applying mental models. “Is this like that app that I use to do…?” People understand and interact with systems and environments based on mental representations they’ve developed from experience.
NO: Designing a UI to support the system model instead of the user's task and perception of the system. Leads to mysterious, confusing controls, and too many of them.
From a design perspective, there are two broad types of mental models; a model that describes how a system works (system model) and a model that describes how people interact with the system (interaction model). Frequently, development teams have a deep understanding of how a system works, but have a weak understanding of how people who will be using the system will expect it to behave. And vice versa; people using the system have a strong sense of how they want it to behave and how they will interact with it but a weak understanding of how the system actually works.
Your goal is to design an interface that merges the system model and the interaction model so that people using the design are successful. The best way to achieve that is to:
- Use the system you design.
- Conduct usability testing of the design.
- Use familiar mental models when appropriate.
- Design with the person’s interaction model as the primary driver.
YES: Designing the UI from the user’s perspective keep’s the design focused and clear.
Note that a UI that successfully merges the system and interaction models may mean that you hide or suppress the system model and focus the UI only on what the person needs to do. You make your system work in the background to complete the task. This can be especially true in a application that must be responsive, since the phone form factor is so small that interactions must be controlled and simplified.
Voice of the Expert:
A well-known usability guru who has been touting the importance of usability testing and mental models for years is Jakob Neilsen. (www.useit.com). Another guru to pay attention to is Jared Spool (www.uie.com). Others include Donald Norman http://www.jnd.org/ and Steve Krug http://www.sensible.com/.