ABSTRACT
We hypothesize that attention is divided into two separable but hierarchically organized networks in which both are involved in action-related processes. The higher-level system is in charge of setting up the task. The two networks share the duty of resolving online competition arising during task performance. The lower-level network (e.g. visual attention) can resolve online conflicts, at both the input and output ends of processing, with a limited set of selection cues. The higher-level network is recruited when these cues are not available. We review the literature and show that our hypothesis is compatible with the available findings. Our hypothesis has clear predictions when two tasks are performed concurrently, as in the psychological refractory period paradigm. We describe experiments, using this paradigm, that support these predictions, and discuss some of the outstanding questions.
