Beginning with cognitive load theory as their motivating scientific premise, researchers such as Richard E. Mayer, John Sweller, and Roxana Moreno established within the scientific literature a set of multimedia instructional design principles that promote effective learning.[4][5][6] Many of these principles have been "field tested" in everyday learning settings and found to be effective there as well.[7][8][9] The majority of this body of research has been performed using university students given relatively short lessons on technical concepts with which they held low prior knowledge.[10] However, David Roberts has tested the method with students in nine social science disciplines including sociology, politics and business studies. His longitudinal research programme over 3 years established a clear improvement in levels of student engagement and in the development of active learning principles among students exposed to a combination of images and text, over students exposed only to text.[11] A number of other studies have shown these principles to be effective with learners of other ages and with non-technical learning content.[12][13]