Perception of Node-Link Diagrams: The Effect of Layout on the Perception of Graph Properties

The way we choose to draw the networks on the plane (layout) is found to be important for the readability of networks by humans. In this study, we examine how different layouts affect our perception of specific properties of small networks of 16 nodes each. We compare a simple grid layout to the planar and force-directed layouts, which are some of the most well-established layout algorithms. We also introduce an alternative 'improved' grid layout, which optimizes the outcome layout in terms of specific aesthetics. When people had to decide whether a network is a tree given a node-link diagram, the layout significantly affected their performance. The same pattern appeared for the detection of the connectedness property. However, when people had to detect two properties at a time, the layout didn't affect their performance. The results show that the layout we choose for representing a network is crucial for our perception of some of the network's basic properties. However, when people had to detect more than one property at a time, the chosen layout didn't seem to significantly affect their performance.