Time and error measures have limitations in revealing in-depth insights into effectiveness of graph visualizations. For better evaluations, this book introduces a cognitive approach. Three evaluations are presented with each using a different method measuring more than just time and error. These methods include purpose-designed questionnaires and interviews, cognitive load measures and eye tracking technology. Contributions of this work fall into two areas: evaluation methodology and domain knowledge. Our methodological contribution is that we define and apply a cognitive approach in...