The potential of online discussions to prompt greater reflection of course material is often stymied by a tendency of students to agree with one another rather than formulating counterarguments. This study reports an experiment using note starters and elaborated cases to encourage counterargumention. A note starter is a drop-down form field that requires students to choose a phrase with which to begin their response. Participants included 48 undergraduates who wrote online discussion notes in response to two issues in educational psychology. Participants also completed a personality survey, based on the five-factor personality model of R. McRae and P. Costa (1997). There was a significant positive main effect of note starters on the frequency of disagreement, as well as personality-treatment interactions between note started and several personality characteristics. The results suggest that note starters are most useful for students with low degrees of curiosity (openness to Ideas) or assertiveness, and who are not overly anxious. Note starters appear to encourage students to consider other points of view during online discussions. (Contains 3 figures, 5 tables, and 50 references.) (Author/SLD)