ABSTRACT
In this chapter we turn to what is one of the two central problems of attention, the other being to what extent attention may be shared between two tasks. Their importance lies in the fact that an adequate knowledge of the answers is required before any model of attention can be constructed. The problem of the switching of attention has been tackled by several workers in the last few years, but with the exception of visually switching attention by fixating different regions of visual space we have at present no completely satisfactory information about it. Until we know more we cannot rule out a 'flip-flop' model of selective attention, unlikely though the latter may be intuitively. If we ask the question 'How exactly does paying attention alter the way in which a subject performs a task?' it is obvious that two essential features of the answer will be how often he can switch his attention from one aspect of the task to another, and how long it may take him to do so.
