This paper reports 2 experiments which investigate the effects of production pacing and arousing content in substance abuse public service announcements (PSAs) on adolescent and college-age viewers 'physiological, cognitive, and emotional responses. Results generally support predictions made on the basis of past research using the limited capacity theory of mediated message processing. One exception is a reversal in the pacing effect on emotional arousal for arousing messages. Adolescents and college-age viewers appear to process messages similarly, with a few exceptions. In particular, adolescent viewers may be more stimulus bound, be more easily aroused, and may process fast-paced messages better than college-age viewers. ' Decades of media research have investigated how different types of media content (news, sports, violence, advertising, etc.) influence people's perceptions, knowledge, emotions, attitudes, and behaviors. In the past few decades, a subset of this research has focused on how the structural features (cuts, edits, sound, light, camera techniques, voice changes, etc.) of media alter viewers' cognitive and emotional pro-) is a Professor in the Department of Telecommunications at lndiana University. Her research focuses on the information processing of mediated messages. Nancy Schwartz (M.A., Arizona State University) is a doctoral candidate in lnstructional Systems Technology and a visiting lecturer in the Department of Telecommunications at lndiana University. Her research interesfs include the use of media for teaching and learning. Yongkuk Chug (M.A., lowa Sfate Universify) is a doctoral candidafe in Mass Conimunication at lndiana University. His research interests include cognitive, emotional, and psychophysiological responses to media messages. Seungwhan Lee (M.A., Korea University) is a doctoral candidate in the Department of Telecommunications at lndiana University. His research interests include new communicafion technologies and media effects.tion research, concerned with how to deliver a message to a target population in order to change beliefs, attitudes, and behaviors, has also paid some attention to how the structural features of messages affect viewers' attention and attitudinal responses, and to the role these play in behavior change. Donohew, Palmgreen, and Lorch (1 994), with other colleagues, have investigated how message sensation value affects emotional responses and message selection. In their work, sensation value is measured with a 17-item scale designed to capture attributes related to a message's formal features. In general, they have found that messages high in sensation value are preferred and may be more effective, particularly with high sensation seeking adolescents who may be more prone to substance use and abuse (Everett & Palmgreen, 1995;Lorch et al., 1994;Palmgreen et al., 1991; Stephenson & Palmgreen, 1999).The message sensation value research has primarily focused on the selection dimension of attention and on attitude and behavior change. The effects of messag...