This research will examine the underlying structure of a domain of cognitive skills referred to as executive function (EF) in normal, young adults. EF skills are presumed to be necessary for the goal-directed, future-oriented behavior that is frequently elicited in novel, non-routine problem-solving situations. Research in neuroscience has suggested that EF skills are mediated by a region of the brain known as the prefrontal cortex (PFC). Based on neuropsychological investigations of individuals with PFC damage or dysfunction, EF has become an "umbrella term" for a wide range of cognitive processes, including: initiation, set maintenance, planning, working memory, inhibition, mental flexibility, and self-monitoring. However, currently there is no universal agreement regarding how to characterize the construct of EF, i.e., the specific cognitive components and the associations among them. This research is based on a theoretical model of the structure of EF. The model includes two basic, "lower level" processes, working memory and inhibition, that make possible the operation of three "higher level" EF components, planning, mental flexibility, and rule induction. The research will test whether this theoretical model of EF is a good "fit" for the actual EF performance of young, adult participants; this model will be tested against two other theoretical models of EF that are prominent in the neuropsychological literature. A total of 300 neurologically normal participants will be recruited from two sites, 150 from the University of Northern Colorado and 150 from the University of Amsterdam. Participants will be asked to perform a set of tasks that represent the five components of EF in the proposed theoretical model. Data from these tasks will be analyzed using structural equation modeling, a statistical technique that can help determine whether the proposed model is a good "fit" or characterization of the pattern of test performance scores. If the experimental tasks are tapping basic neural functions, then the model of EF underlying this research should fit the data from both test sites (Colorado and The Netherlands). If two different models of EF are suggested by the data from the two sites, then the contributions to EF of variables such as intelligence, motivation, etc., need to be explored. The potential impact of this study is to provide a window on the composition of the EF domain and, indirectly, the functioning of the highly interconnected PFC in normal, young adults. This POWRE grant will provide access to special facilities (participants at the University of Amsterdam) and special methodologies (training in structural equation modeling), it will foster an existing international collaboration, and it will provide focused support at a critical stage of a 15-year research program investigating the nature of EF.
