My goal in this book has been to systematically review the empirical literature on group task performance. The central question I have tried to address is whether or not there is an inherent benefit to collaborative work arrangements. In its barest form, this question asks whether or not interaction among members adds anything to a group’s task performance that would not be provided simply by combining the separate (noninteractive) efforts of its individual members. I have considered this question in the context of a range of tasks (idea generation, problem solving, judgment, and decision making), as well as from several different process perspectives (learning and memory, motivation, and member diversity).