Collective Intelligence (CI) is the ability of a group to exhibit greater intelligence than its individual members. Expressed by the common saying that "two minds are better than one," CI has been a topic of interest for social psychology and the information sciences. Computer mediation adds a new element in the form of distributed networks and group support systems. These facilitate highly organized group activities that were all but impossible before computer mediation. This paper presents experimental findings on group problem solving where a distributed software system automatically integrates input from many humans. In order to quantify Collective Intelligence, we compare the performance of groups to individuals when solving a mathematically formalized problem. This study shows that groups can outperform individuals on difficult but not easy problems, though groups are slower to produce solutions. The subjects are 57 university students. The task is the 8-Puzzle sliding tile game.