Measurement effects exist throughout the sciences-the act of measuring often changes the properties of the observed. We suggest emotion research is no exception. The awareness and conscious assessment required by self-report of emotion may significantly alter emotional processes. In this study, participants engaged in a difficult math task designed to induce anger or shame while their cardiovascular responses were measured. Half of the participants were asked to report on their emotional states and appraise their feelings throughout the experiment, whereas the other half completed a control questionnaire. Among those in the anger condition, participants assigned to report on their emotions exhibited qualitatively different physiological responses from those who did not report. For participants in the shame condition, there were no significant differences in physiology based on the self-report manipulation. The study demonstrates that the simple act of reporting on an emotional state may have a substantial impact on the body's reaction to an emotional situation.