Recent interest in the development of visual and auditory communication systems has led to a consideration of the relative efficiency of vision and audition under conditions of simultaneous stimulation. It has often been shown that a combined visual and auditory presentation of the same material results in better comprehension than the presentation of either auditory or visual material alone (2). Very little is known, however, about the relative performances of these two modalities when they are simultaneously stimulated by conflicting material. Recently, Mowbray (10) has shown that for combined tasks involving more than one level of difficulty, significant deterioration of performance, compared to that with nonsimultaneous presentation, caused by the conflicting nature of the material occurred with the easier of the tasks. No differential modality effects were detected. That is to say, deterioration of performance from nonsimul-