What's interesting to me is that this is true no matter what tools they used and regardless of the complexity of the system.
Tools didn't matter: Whether people made diagrams with paper cutouts, online diagramming tools or pencil and paper, the result was the same.
The complexity of the system didn't matter: Whether people were diagramming something as simple as a pencil sharpener or as complex as the British Parliamentary system, it did not seem to have much effect on the complexity of the diagrams they used to represent the systems.
In fact the only thing that did seem to affect the number of nodes people used is when the experimenter instructed them to take as long as they needed and to make diagrams that were as detailed as possible. And even then the number of nodes maxed out at about 13.
This is worth thinking about if you are going to use diagrams to communicate with other people. What insights can we glean from this? Here are some of my thoughts:
1. People construct "mental models" when trying to understand how things work
2. Most mental models seem to be made up of 6-12 components
3. A diagram with more then 13 components will probably not become integrated into people's consciousness as a mental model
To me, that means that if you want your system to be understood and integrated into people's thinking as a mental model,
you had better boil it down to a simple picture.
The study -- Correction: A picture is worth 84.1 words -- was conducted by Cambridge researcher Alan F. Blackwell and funded by the Medical Research Council and Hitachi Europe Ltd. Update: Alan suggested I point out that he was a Ph.d. student at the time this study was conducted -- more recent research can be found on his website.
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