Graphs have become a fixture of everyday life, used in scientific and business publications, in magazines and newspapers, on television, on billboards, and even on cereal boxes. Nonetheless, surprisingly few graphs communicate effectively. Many graphs fail because they do not take into account the goals, needs and abilities of the viewers. This book addresses the problems that arise when we attempt to convey information with visual displays such as graphs by presenting eight psychological principles for constructing effective graphs. These principles are solidly rooted in the scientific literature on how we perceive and comprehend graphs, and also in general facts about how our eyes and brains process visual information. The principles lead to hundreds of specific recommendations that serve as a concrete, step-by-step guide to constructing graphs that will be understood at a glance, help the reader decide whether a graph is an appropriate display for their information, and help the reader to choose the correct type of graph for a specific type of data and message. These psychological principles can be used to construct not only effective graphs, but also effective maps, diagrams, and other types of visual displays.