Viewer Watches Anti-Tobacco Ad (image) University of Missouri-Columbia Caption The researchers measured the physiological responses of viewers while the viewers watched a series of 30-second anti-tobacco ads. Electrodes were placed on the viewers' facial muscles to measure emotional responses. Attention, which was defined as the amount of mental effort participants expended to interpret the messages, was measured by taking participants' heart rates. Credit PRIME lab, Missouri School of Journalism Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.