Group structure is one of the important mediators between individual input and group output. The present study examines the effect of group structure on the following dependent variables: (1) change in the group member's evaluation of items evaluated before group interaction, (2) change in his subjective evaluation model as a consequence of group interaction, (3) group (collective) evaluations, and (4) group efficiency measured in terms of the amount of time required to complete the group task. The results of the study corroborate previous findings of the positive performance effects of decentralized group structures on complex tasks. (Author)