The purpose of the present study was to examine the erects of the physiological arousal and the priorsubconscious processing of hostility-related words upon the cognitive complexity in person perception. First, sixteen male and 16 female college students performed a cognitive task in which they processed hostility-related words or neutral words unconsciously in a high arousal or a normal arousal state. In the second ostensibly unrelated task, the subjects were presented with an ambiguous description of target person's mild hostile behavior and they were asked to rate the impression of the target person on several SD-trait scales. It was found that the higher the subjects' arousal level was, the simpler the cognitive complexity became. Also, when the subjects processed neutral words in the high arousal state, individual differences of the impression were the largest. The effects of hostility-related words to decrease the individual differences in the high arousal state, however, were not found. These results indicate that physiological arousal may have an important role in the mechanisms of social cognition.