Group disaster Mary, Jane, Janet and Samantha chose each other for a group project since they knew that they were all high achievers. Once the project rolled around however, their group actually did more poorly than the group where all the members knew that others were slackers. How did that happen?

Given that Mary, Jane, Janet and Samantha chose each other for the fact that they considered the others good students or high achievers, the opportunity cost of slacking, for each of them individually dropped drastically, since they expected the others to be responsible. Given that each of them symmetrically thought the same way, all of them jointly tried to free-ride on the other members' contribution resulting in no work getting done. However, in the group where everyone knew that the others were slackers, each of them worked hard since they knew that the others might not, resulting in everyone working hard and a better outcome.