Remember The Grudgers Chapter 10

Remember the Grudgers of Chapter 10. These were birds that helped each other in an apparently altruistic way, but refused to help - bore a grudge against - individuals that had previously refused to help them. Grudgers came to dominate the population because they passed on more genes to future generations than either Suckers (who helped others indiscriminately, and were exploited) or Cheats (who tried ruthlessly to exploit everybody and ended up doing each other down).

In the example, three categories of behavior are identified: Cheats, Suckers, and Grudgers. Cheats attempted ruthlessly to take advantage of everybody. Suckers aided others without discrimination, and were taken advantage of. The behavior of Grudgers they replicated accurately