© Springer International Publishing AG, part of Springer Nature 2018. The effects of group size on performance and member satisfaction were assessed, with group size ranging from an individual to five members. Participants were 96 university students who engaged in a furniture-assembly task. Our results showed that group size had negligible effects on member satisfaction but strong effects on performance characteristics. As group size increased, performance characteristics, time-to-completion, and duration of interaction with materials decreased in an exponential manner, although member satisfaction tended to become saturated. The result for duration of interaction with materials suggested that the social loafing effect increased with the size of the group. We expect these results to be helpful in designing relationality for collaborative problem solving among people as well as between people and artifacts.