Comprehension can be the starting point for further cognitive activities such as thinking and problem-solving. Productive thinking requires a specific interaction between descriptive and depictive representations combining representational power and inferential power. The interaction takes place through processes of mental model construction and model inspection. Descriptive representations are combined and coordinated with the corresponding depictive representations, whereby each representation constrains the construction and usage of the other representation. Model inspection requires systematic and exhaustive interrogation of depictive representations in order to read off relevant information. Depictive representations have to grasp task-relevant structures and facilitate performance of the required procedures. Required operations should not be difficult to perform and the sequences of operations should be relatively short. Inappropriate perceptual structures of visualizations can obscure relevant structural attributes, preventing the application of correct procedures and stimulating the application of incorrect procedures.