This study investigated the effects of multimedia presentations on the efficiency of learning scientific information (i.e. information on basic anatomy of human brains and their functions, the definition of cognitive psychology, and the structure of human memory). Experiment 1 investigated whether the modality effect could be observed when the learning material contained auditory information and visuals altered in complexity, and whether the redundancy effect is caused by redundant information or by interference in information processing. In Experiment 2, verbal-only information was used to examine whether subjects could perform better with auditory rather than with on-screen textual information, and whether the length of the verbal information would exert an effect on learning. The results of Experiment 1 contradicted the prediction of the modality effect in that subjects learned no better or even worse with the audio-visual format of learning material than did subjects with the visual-only one. Besides, redundant information per se did not impair learning, which suggested that the redundancy effect could be rather caused by the interference in information processing. The results of Experiment 2 indicated a negative effect of auditory information on learning regardless of the length of the verbal information. No evidence supported the superiority of auditory instructional mode over the visual one. (Contains 6 tables and 8 figures.)