The focus of Infovis research is on external visualizations and interactions, but it is argued that developing internal representations is necessary, though not looked at. The term mental model is a small scale internal representation of a real-world phenomenon. Mental models must be functional, though not accurate, ways that lead reasoning.
The definition of mental model in context of Infovis is: a functional analogue representation to an external interactive visualization system with the following characteristics: structural/behavioral properties of the system are preserved, schematic, semantic, or item specific information of the underyling data can be preserved, and given a problem, a mental model can be constructed and simulated in working memory for reasoning. Stasko suggests four possible high-level dynamic interactions between mental models and external visualization: internalization, processing, augmentation, and creation.
Internalization: The formation of a mental model happens off of the appearance of the original external phenomenon. We first must learn how to interpret the system, then (if successful) we internalize a mental model that reflects this (functional) perception.
Processing: Internalized mental models can process and make sense of new external phenomena including visualizations. Depending on the way it is visualized, a mental model may be able to interpret new external visualization.
Augmentation: Mental models can be made and simulated in reasoning and sensemaking. Pure mental modeling is usually not sufficient, and external visualizations can augment them to make a couple cognitive system.
Creation: Mental models can serve as the cognitive basis of creativity and innovation. They can give rise to new concepts and designs (including new visualizations).
As mental models are functional, but usually insufficient, external visualizations are needed to augment them. Interaction is not a delegate of the cognitive process, it is a central part of it. The proposed three primary functionalities of interaction are to enable: external anchoring (projecting of mental structures onto visual forms and/or locating generated appropriate representational anchors), information foraging (a restructuring [reconfigure and encode from Stasko 2007] and/or exploring of data to make a hypothesis), and cognitive offloading (creation of a visual representation and/or save/load specific states of a visualization).
These all must be considered when designing Infovis systems, and thus sets up a framework that unites visualizations, mental models, interaction, and the analytic process in a coherent account.
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