Cooperative learning capitalizes on the relational processes by which peers promote learning, yet it remains unclear whether these processes operate similarly in face-to-face and online settings. This study addresses this issue by comparing face-to-face and computer-mediated versions of "constructive controversy", a cooperative learning procedure designed to create intellectual conflict among students. One hundred and one undergraduates were randomly assigned to a 1 (control: face-to-face) x 3 (medium: video, audio, text) x 2 (synchronicity: synchronous, asynchronous) experimental-control design. Cooperative perceptions declined and individualistic perceptions increased under asynchronous computer-mediated conditions, resulting in predicted declines in motivation (i.e., relatedness, interest, value) and academic achievement (i.e., completion rate). For practice, findings suggest that synchronicity but not medium plays an important role in computer-mediated constructive controversy. For theory, findings also suggest that social psychological theories based on face-to-face assumptions may need to be modified to indicate that predicted outcomes depend on synchronous social interaction. (Contains 2 figures and 4 tables.)