Thinking about attention: Successive approximations to a productive taxonomy.

Attention, the recruitment of processing resources, is viewed as pivotal for understanding normal behaviour and thought as well as the disorganizations associated with brain damage and disease. A brief history foreshadows aspects of a proposed taxonomy of attention that builds upon Posner's tripartite taxonomy. Posner's influential taxonomy views attention as a set of isolable neural systems (alerting, orienting and executive control), often working together to organize behaviour. For measuring the efficacy of these three networks, Posner and colleagues created the Attention Network Test (ANT). The impact of the taxonomy and this model task for exploring it is illustrated by the facts that they have spawned numerous variants designed for different purposes and that one or another variant has been used in almost a thousand publications. We have previously built upon this conceptual framework by considering: two modes of control over resource allocation which we labelled exogenous and endogenous and three domains over which these modes of control are presumed to operate (space, time and task or activity). The Combined Attention Systems Test (or CAST) was developed to measure the efficacy of the six kinds of attention implied by revised taxonomy. Lastly, this taxonomic effort is further developed by incorporating the distinction between overt, observable behaviour in the "real" world and covert "behaviour" in the realm of thought and imagination.