4. Research has the purpose of revealing: (a) ways in which existing media can be most effectively employed in promoting effective human learning; (b) the conditions of optimal learning, including the properties and characteristics of media that can be used to establish such conditions; and (c) novel techniques of designing and delivering instruction that can be shown to improve its effectiveness.5. On a rational basis, the media selected for instruction should be those whose characteristics best fulfill the requirements for providing the conditions of most effective learning. It is recognized, however, that practical considerations such as availability and cost sometimes dictate media choices. In such instances, the question to be asked changes to the following: Given these media, how can they best be used in delivering a specified module of instructional content?6. Evaluation studies of the use of media have frequently failed to show an advantage for media-based versus non-media-based instruction. It is believed that these studies may have been inadequately formulated. Remaining as questions of high promise for research are those which investigate innovative ways of utilizing particular features of media (e.g., audio and visual coordination, pacing of learner responses, variations in feedback, flexibility or practice examples, elaboration of factual knowledge) to enhance the effectiveness of learning conditions. Such studies may lead to innovative procedures for using existing media, as well as to novel modifications of equipment.7. A goal of research and development in instructional technology continues to be the ideal of being able to specify the characteristics of a system of media that would make possible a set of conditions for optimally effective learning that would exceed the capabilities of instructor-mediated instruction. Such a system would be aimed at many (but not necessarily all) learning goals. Properties of modern communications and computer equipment, as well as discoveries in human cognition, provide many prospects for the development of a media system for optimal instruction of this sort.