Although verbal learning offers a powerful tool, Mayer explores ways of going beyond the purely verbal. Recent advances in graphics technology and information technology have prompted new efforts to understand the potential of multimedia learning as a means of promoting human understanding. In this second edition, Mayer includes double the number of experimental comparisons, 6 new principles - signalling, segmenting, pertaining, personalization, voice and image principles. The 12 principles of multimedia instructional design have been reorganized into three sections - reducing extraneous processing, managing essential processing and fostering generative processing. Finally an indication of the maturity of the field is that the second edition highlights boundary conditions for each principle research-based constraints on when a principle is likely or not likely to apply. The boundary conditions are interpreted in terms of the cognitive theory of multimedia learning, and help to enrich theories of multimedia learning.