- It is hypothesized that ratings of emotional stimuli are affected by a constant threat of traumatic events. Ratings of valence and arousal on the International Affective Picture System from young adults in the United States were compared to those of young Israeli adults. Israelis rated the pictures as less negative and less positive than did participants from the United States. Israeli women gave higher arousal ratings compared to the American women. These differences may be due to compulsory military service in Israel, during which exposure to traumatic events is more likely to occur, and to the timing of the study which followed a year of frequent suicide bomb attacks. The authors suggest that these findings may reflect mild symptoms of stress disorders.