Although impulsivity is recognised as a major psychopathological feature, its cognitive correlates remain controversial. We evaluated readiness to act induced by a warning signal and attentional engagement in healthy impulsive participants.People with high impulsivity scores (HI) and low impulsivity (LI) scores on Barratt's Impulsivity Scale (BIS) were selected among 1250 students from top and bottom deciles. Subjects with personal or family of lifetime Axis I disorders were excluded. Motor preparation was evaluated by a Choice Reaction Time task (CRT) with a randomly presented warning signal with a delay before target of 500 ms or 2000 ms depending on the trial block. Attentional engagement and maintenance of fixation was evaluated by a Cued Target Detection task (CTD) comparing cued (valid, invalid, or double cue) and uncued trials and contrasting fixation offset (gap) or maintenance (overlap) conditions.HI, but not LI participants had a shortened reaction time in the 2000 ms condition of CRT with warning signal, indicating a persistent readiness to act. In contrast to LI, HI showed a decreased reinforcement of attention in the overlap condition of CTD with a hyperreactivity to all types of visual stimuli.Impulsivity per se appears to be associated with hyperreactivity to warning or cue signals and on inability to maintain attentional fixity.