In 2 experimental studies, social indispensability and upward social comparison were contrasted as potential triggers of motivation gains of inferior group members. Using a cognitive task in a computer-supported environment, individual work was compared with conditions that enabled upward comparison only (coaction), or both upward comparison and social indispensability (conjunctive task). Moreover, working conditions (face-to-face vs. anonymous) and partner-related performance feedback (contemporaneously vs. post-task) were manipulated as potential moderators. Results revealed motivation gains only when partner feedback was contemporaneously available. In this case, upward-comparison effects could be demonstrated during coaction. However, when participants' contribution determined a group outcome, their motivation was additionally increased, demonstrating social indispensability effects. Finally, motivation gains were generally higher during face-to-face compared to anonymous work.