Mental Model Diagrams rely on the fact that people behave in ways that are consistent with core beliefs they hold to help visualise the causes of their behaviours and develop solutions that meet their needs. Mental Model Diagrams are detailed summaries of the behaviours, beliefs and emotions that relate to specific tasks undertaken by that person and in turn to specific design features (in the bottom half of the example above). Such diagrams help designers to focus on product development strategies that reflect the reality of how people feel, think and act in relation to specific jobs in their lives.As with all research, it is important to identify the right group to study (called task-based audience segments in the parlance of Mental Model Diagrams). Diagrams are then used to evaluate existing products and services and their ability to meet the needs of target segments. The development of such segments helps identify the right people to recruit for later test work including interviews, card sorts and usability tests. Typically at least four people are used within each task-based segment.
The diagrams are built from the bottom up, using behaviours, beliefs and emotions as building blocks (including actions, thoughts, feelings and motivations). It is important to understand the differences between segments and their behaviours and then organise the diagram to reflect such differences.
The end result is to highlight the differences between segments and the root causes of these differences and the behaviours themselves. This is a useful tool when there are clear existing segments who accomplish similar tasks in different ways and with different motivations, helping designers to develop solutions that reflect the needs of multiple segments in relevant ways rather than producing one “average” and compromised solution that ultimately satisfies no one.
Universal Methods of Design by Martin & Hanington
Mental Models: Towards a cognitive science of language, inference and consciousness by Johnson-Laird