Gave 10 Ss a series of different innocuous visual and auditory stimuli in a session at the beginning and again at the end of the academic quarter. For 1/2 of the Ss, graduate students, the 2nd session preceded a final oral examination for a seminar in which they were enrolled. For the remaining Ss, undergraduate students, the 2nd session was simply a repetition of the 1st. Measures of the GSR and cephalic vasomotor activity obtained during the habituation and oral examination sessions were taken as indices of phasic and tonic orienting and defense reflexes. Undergraduates showed slower habituation of the GSR and smaller pulse widths than graduates during the 1st habituation session. In the 2nd habituation session, graduates showed slower habituation of the GSR and smaller pulse widths than the undergraduates. These Group * Sessions interactions suggest that habituation of the orienting reflex is influenced by the arousal state of the individual and by parameters of the physical stimulus. (PsycINFO Database Record (c) 2006 APA, all rights reserved)