Attentional limitations in dual-task performance.

People's ability (or inability) to do different activities or tasks at the same time is a topic of much interest not only to psychologists, but also to the proverbial person in the street. It is natural to wonder about what we as human beings can and cannot do. An understanding of our limitations should also have practical value, because the intelligent design of human/machine systems depends as much on knowing the capabilities of people as it does on knowing the capabilities of machines. Human performance limits have played an important role in catastrophes that have occurred in aviation and other fields; a better understanding of those limits might help in designing systems and procedures that can minimize the frequency of such disasters. Simultaneous performance of different tasks is intellectually intriguing as well. The limitations on simultaneous cognition may provide important clues to the architecture of the human mind. The notion that dual-task performance limitations have implications about the unity of the mind occurred to people long before the present era of information-processing psychology. In the late nineteenth century, for example, the educated public was fascinated with a phenomenon called automatic writing, in which People were claimed to be able to write prose while carrying out other tasks (see Koutstaal, 1992). This chapter provides an overview of research on attentional limitations dual-task performance. The organization of the chapter follows a plan