The “Map” in the mental map: Experimental results in dynamic graph drawing

•We summarize experiments that test mental map preservation in dynamic graph drawing.•No experiment has found a positive effect of the mental map on undirected graphs.•More than 3–5 elements should be involved to offload mental effort to the diagram.•Tasks that require orientation in the information space should be tested.•Mental map preservation may be more related to task than previously thought.

Preserving the mental map is frequently cited by dynamic graph drawing algorithm designers as an important optimization criterion. There have been a number of definitions for mental map preservation and many different algorithmic approaches to drive dynamic graph drawing to satisfy these definitions. One of the most frequently used definitions is that of Coleman and Parker where “the placement of existing nodes and edges should change as little as possible when a change is made to the graph.” A number of experiments have been run to test the effectiveness of this definition from a usability perspective. To date, no experiment has found conclusive evidence that supports the effectiveness of the mental map in the comprehension of a dynamic graph series. In this paper, we summarize the experiments conducted on this definition of mental map preservation and provide recommendations to designers and researchers to fully understand when the mental map supports user tasks.