Alais, D., Morrone, C. & Burr, D. (2006).

Separate attentional resources for vision and audition,Proc Biol Sci, 1592 (273), 1339-1345. 

Current models of attention, typically claim that vision and audition are limited by a common attentional resource which means that visual performance should be adversely affected by a concurrent auditory task and vice versa. Here, we test this implication by measuring auditory (pitch) and visual (contrast) thresholds in conjunction with cross-modal secondary tasks and find that no such interference occurs. Visual contrast discrimination thresholds were unaffected by a concurrent chord or pitch discrimination, and pitch-discrimination thresholds were virtually unaffected by a concurrent visual search or contrast discrimination task. However, if the dual tasks were presented within the same modality, thresholds were raised by a factor of between two (for visual discrimination) and four (for auditory discrimination). These results suggest that at least for low-level tasks such as discriminations of pitch and contrast, each sensory modality is under separate attentional control, rather than being limited by a supramodal attentional resource. This has implications for current theories of attention as well as for the use of multi-sensory media for efficient informational transmission.