• anonymity;
  • computer-mediated communication;
  • group awareness;
  • portraits;
  • SIDE-model;
  • social categorization;
  • social dilemma;
  • social identity theory;
  • social value orientation

Abstract Knowledge exchange with shared databases can be seen as a public-goods dilemma. People are reluctant to contribute information because they save time, effort and perhaps social power if they withhold their knowledge and socially loaf. But if all people choose this individually efficient strategy, then no information exchange can take place, and the group is less effective than it would have been if all members contributed. Thus, in the knowledge-exchange situation, group norms and individual norms oppose each other.

In order to strengthen people's orientation towards the group, virtual collaborative tools sometimes provide member portraits. But based on the Social Identity Model of Deindividuation Effect (SIDE)-Model, ambivalent effects of these member portraits are expected according to people's social categorization: when people identify more strongly with the group, such portraits enhance participation, whereas when people have a stronger individual identity, they undermine participation.

This study links the concepts of social value orientation to identity salience. The assumption is that in the information-exchange dilemma, the social value orientation of a group member will determine whether group identity or individual identity becomes salient for that group member. We then extend the SIDE-model to the domain of social loafing and expect that portraits of the group members will have different effects for people with individual orientation and for people with prosocial orientation. An experiment confirmed this expectation and revealed a significant interaction between social value orientation and portraits. Especially striking is the result that for prosocials the provision of member portraits leads to an increase in social loafing. This is analogous to the predictions of the SIDE-model.