Most studies of behavior examine task operations without addressing the central question of control. That is, it is usually assumed that the control process that sets and schedules task operations so that the organism behaves in a coherent, goal-directed fashion need not be theoretically addressed to understand a particular behavior. For example, when we study performance during a choice reaction task, we do not concern ourselves with the mechanisms that enable the subjects to follow the instructions and set-up the S-R mappings. However, researchers are quickly coming to understand that an account of these operations is absolutely necessary to explain behavior.

In practice, the concept of executive control is often closely linked to the concept of attention -- both terms are usually very loosely defined. Both processes can serve to gate information to the appropriate neural systems and filter out information that might negatively affect performance. Executive control can be thought of as the mechanism controlling the deployment of attention, but there are no hard definitions demarking where one process ends and the other begins.

In our lab, we study sequential effects to gain a window onto control processes. In response conflict tasks, such as the Simon task and the flanker task, compatibility effects are larger following congruent trials than after incongruent trials. Thus, it appears as if some control process monitors conflict and adjusts the level of control dynamically, although other explanations of these sequential effects have been put forward.

Our lab is working to gain a better understanding of sequential effects and to learn whether they reflect the modulations of a control process or priming effects specific to particular stimulus categories and responses. We are also examining whether sequential effects can be disrupted by the imposition of a secondary task, particularly a secondary task that is also assumed to tax executive control processes.

It is an open question whether a common set of control processes is engaged across distinct tasks. Our research aims to address this issue and to determine if one can speak meaningfully about "executive control" processes, or if the term simply refers to a diverse collection of mental operations that are poorly understood.

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Hazeltine, E., Bunge, S. A., Scanlon, M. D., & Gabrieli, J. D. E. (2003). Material-dependent and material-independent selection processes in the frontal lobes: an event-related fMRI investigation of response selection.  Neuropsychologia, 41, 1208-1217.

Bunge, S. A., Hazeltine, E., Scanlon, M. D., Rosen, A. C., & Gabrieli, J. D. E. (2002). Dissociable contribitions of prefrontal and parietal cortices to response selection. NeuroImage, 17, 1562-1571.

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