Conceptual models is the generic term that describes the various ways in which systems are understood by different people. Primarily these consist of the way users conceptualize and understand the system and the way designers conceptualize and view the system.
As I said in my previous article, whether interacting with devices, machines, computers, people, or the physical world, people use their prior knowledge to develop mental models to enable them to understand and predict their behavior. A successful approach in interface design is to capitalize on users' existing knowledge and the use of metaphors. The aim of designers is to help users develop accurate mental models of the system. As Donald Norman (1986) puts it, "The problem is to design the system so that, first, it follows a consistent, coherent conceptualization - a design model - and, second, so that the user can develop a mental model of that system - a user model - consistent with the design model".
Users' models, design models, and the system image
An important consideration of conceptual models is the relationship between designers' models - the design model - and users' mental models - the user's model shown in the picture below. As most designers work in teams, it is more accurate to consider the design model as the product of a collection of individuals rather than the outcome of any one individual. Ideally, the user model should map onto the design model. That way the users will be able to use the system's full capability as intended by the designer. However, in the real world, this does not happen. More often, users only develop a partial mental model of the design model. Their understanding and ability to use the system, therefore, is limited. Another problem is that the design model may be inappropriate for what the user wants to achieve. In this situation, the users are forced to develop a mental model that is unfamiliar to them. A mismatch can also arise if the design model is ambiguous, inconsistent, or obscure. Generally, the way users get to find out about the design model is through the interface, its behavior, and the documentation. Collectively, these are called the system image.
A large part of the accessible system image comprises the physical interface (the knobs and dials or images on a screen). It is important to bear in mind, that the system image also includes the system's behavior, that is, the way it is used (by pressing keys, moving a mouse, and so on). The sequence of operations required in using the system (commands or menu selections) and the resulting events are all part of the system's image, and users learn not just from looking at the system but also from their experience of using it.
If the system image is not able to convey to the users the design model in a clear and obvious way, then it is likely that the users will develop incorrect mental models. Consequently, they will experience great difficulties in understanding and using the system.
Conceptual Models Diagram from Norman, D. A. (1988). The Design of Everyday Things. New York, Basic Books.
Design is a quest to find the best possible match between the user’s mental model that they have in their mind, and the conceptual model that you’re presenting to them with your product.
It’s as if you’ve put the oven in the bathroom, and the shower in the kitchen — UX researcher, Dylan Mathiesen
How to build a strong conceptual model
Start from the end. Establish the goal. Who is the product for? What does it do for them?
Brainstorm. Create a simple model. Get input from team members. Add details as needed.
Evaluate. Do you understand the concept? Do team members understand the concept? Does the model communicate it clearly?
Iterate. You may need several versions before finding the best way to convey the idea.
Mediating between users’ mental models and the system’s conceptual model is essential, and it shouldn’t happen as an isolated activity. It should be part of a larger practice of design, planning, communicating, and delivering in a way that supports users. For UX and UI designers, a conceptual model is the first step in communicating what you want the system to do for the user.