A phasic change in alertness is produced every time that a warning stimulus precedes a target, and it enhances and maintains the response readiness to an impending stimulus. In the present study, we investigated the Contingent Negative Variation (CNV) phenomenon, as index of phasic alertness, during a S1-S2 paradigm in which the imperative stimulus was represented by a double-choice reaction time task, designed to increase the executive requests at S2. Subjects performed the task at three consecutive time points in order to explore the CNV activity over time. The repetition of a cued double-choice reaction time task reduced the reaction times (RTs), while CNV amplitude remained steady along the sessions. Our data suggest that the continuous recruitment of attentional resources does not undergo habituation when it is related to the brain activity required in the maintenance of working memory when the mental model of the stimulus environment is updated. © 2014 Elsevier Ireland Ltd.