This article presents Second Messenger, a system of dynamic awareness displays that reveal speaker participation patterns in a face-to-face discussion. The system has been used by a variety of groups during face-to-face meetings, increasing individuals ’ awareness of their own and others ’ participation in discussions. Experimental results indicate that these displays influence the amount an individual participates in a discussion and the process of information sharing used during a decision-making task. These findings suggest that awareness applications bring about systematic changes in group communication styles, highlighting the potential for such applications to be designed to improve group interactions. Joan DiMicco is an HCI researcher interested in human–human communication; she is a researcher at IBM Research in Cambridge, MA. Katherine Hollenbach is an undergraduate at MIT with an interest in computer science and design; she is an undergraduate researcher at the MIT Media Lab. Anna