Most of the research done up to now with regard to the choice of media has been either at the level of the audience or at the level of communication. Audience surveys of major media categories are necessary, but they are not sufficient. Large-scale surveys which seek to compare the general effectiveness of several media categories sometimes lead to disappointing conclusions. In order to make progress, we must study the working of the actual process of communication; we must know the why and how of effectiveness. Consequently the media planner will henceforward need the help of the psychologist, the sociologist and the semiologist.