Known as hidden profiles problem in group decision-making, a group tends to retrieve and discuss information that are known to majority of the group members and omit or neglect unique information to individuals which leads to the correct solution. Prior studies have shown that validity of the unique information is one key factor of the hidden profiles problem. In an attempt to address hidden profiles problem in computer-mediated communication, this paper presents a work-in-progress tool, Rationale Flower that visualizes the rationales exchanged through instant messaging in an online group decision making activity. In this study, a rationale is a member's explanation of why a piece of information should be brought to the group discussion. By this definition, it is expected that visualizing the members' rationales will not only attract group members' attentions to them but also support the group to testify and validate the unique information.