The 4th edition of the Handbook of Research on Educational Communications and Technology expands upon the previous 3 versions, providing a comprehensive update on research pertaining to new and emerging educational technologies. Chapters that are no longer pertinent have been eliminated in this edition, with most chapters being completely rewritten, expanded, and updated Additionally, new chapters pertaining to research methodologies in educational technology have been added due to expressed reader interest. Each chapter now contains an extensive literature review, documenting and explaining the most recent, outstanding research, including major findings and methodologies employed.    The Handbook authors continue to be international leaders in their respective fields; the list is cross disciplinary by design and great effort was taken to invite authors outside of the traditional instructional design and technology community.