There have been multiple theories regarding divided attention. One, conceived by Kahneman ,  explains that there is a single pool of attentional resources that can be freely divided among multiple tasks. This model seems to be too oversimplified, however, due to the different modalities (., visual, auditory, verbal) that are perceived.  When the two simultaneous tasks use the same modality, such as listening to a radio station and writing a paper, it is much more difficult to concentrate on both because the tasks are likely to interfere with each other. The specific modality model was theorized by Navon and Gopher in 1979. However, more recent research using well controlled dual-task paradigms points at the importance of tasks.  Specifically, in spatial visual-auditory  as well as in spatial visual-tactile tasks  interference of the two tasks is observed. In contrast, when one of the tasks involves object detection, no interference is observed.  Thus, the multi-modal advantage in attentional resources is task dependent.