Forty male and forty female postgraduates served as subjects in a 2 X 2 X 2 factorial experiment. Each subject received either high or low intensity of electric shock input for long or short exposures. The immediate recall of 7 lettered paired words was used as index of vigilance. It was found that: the exposure and the shock inputs conjointly determined the coping strategy of vigilance; the male subjects evoked more vigilance responses with high intensity of shock in the long exposure, whereas the female subjects did so with low intensity of shock; and the reduction of uncertainty facilitated vigilance.