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Two voluntary task-switching experiments probed the influence of previous exposures to stimuli and categorizations of these stimuli on task choice during subsequent exposures to the same stimuli. Subjects performed origin and size judgments under standard voluntary task-switching instructions to perform the tasks equally often in a random order. Both when subjects voluntarily selected the task on the first exposure (Experiment 1) and when the experimenter manipulated the task on the first exposure (Experiment 2), subjects chose to perform the same task on subsequent exposures significantly more often than would be expected on the basis of the instructions to perform tasks in a random order. Presentation of a previously encountered stimulus may result in the retrieval of a stimulus-task binding or event file that biases task selection as well as task readiness. The pattern of data across the 2 experiments suggests that stimulus-based priming influences task choice through both retrieval of episodes within the context of the experiment and semantic memory mechanisms.

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Traumatic brain injury (TBI) is a major public health concern in both civilian and military populations. Recently, genetics studies have begun to identify individual differences in polymorphisms that could affect recovery and outcome of cognitive and social processes following TBI. This review considers the potential for polymorphisms to influence six specific cognitive and social functions, which represent the most prominent domains of impairment following TBI: working memory, executive function, decision making, inhibition and impulsivity, aggression, and social and emotional function. Examining the influence of polymorphisms on TBI outcome has the potential to contribute to an understanding of variations in TBI outcome, aid in the triaging and treatment of TBI patients, and ultimately lead to targeted interventions based on genetic profiles.