In groups, people might not contribute equally to shared resources even if they genuinely want to help others out. When both selfless and selfish people are in a group, the greedy folks often take advantage of the selfless actions, leading to less public goods being provided, especially in large groups. The only time when selfish people might not exploit the generosity of others is when so many selfless acts are expected that it just makes sense for the selfish ones to give in, too. In most cases, though, when there are both generous and self-centered individuals in a group, the selfish ones benefit the most, and public goods suffer, especially in bigger groups.