Perception of Symmetries in Drawings of Graphs

TL;DR

This study investigates human perception of different symmetry types in graph drawings, revealing vertical reflective symmetry as most salient and rotational symmetry perception influenced by the number of axes.

Contribution

It provides empirical evidence on the salience of symmetry types in graph perception and how the number of axes affects rotational symmetry recognition.

Findings

Vertical reflective symmetry is most salient.

Rotational symmetry perception increases with more axes.

An exception occurs at four axes for rotational symmetry.

Abstract

Symmetry is an important factor in human perception in general, as well as in the visualization of graphs in particular. There are three main types of symmetry: reflective, translational, and rotational. We report the results of a human subjects experiment to determine what types of symmetries are more salient in drawings of graphs. We found statistically significant evidence that vertical reflective symmetry is the most dominant (when selecting among vertical reflective, horizontal reflective, and translational). We also found statistically significant evidence that rotational symmetry is affected by the number of radial axes (the more, the better), with a notable exception at four axes.