In chapter 4, mobile individuals again face the Prisoner's Dilemma. Though moving about, individuals are again able to identify each other and record past experiences of interaction. In a second variant, individuals keep co-operating or defecting as long as their payoffs meet a certain aspiration level. In each period, there is a certain probability that the attainment of this aspiration level will be monitored. If the aspiration level is not met, individuals will change their strategies.
Individuals have a certain number of attributes which are represented by integer values.
If an individual's neighbourhood is not similar enough in terms of attributes, then that individual will migrate. In a second variant, the individuals do not look for similarity but become more similar by 'moving towards' the average attribute values in their neighbourhoods. Chapter 6 gives up locality of both interaction and movement. Instead, individuals interact with their friends who can live anywhere on the grid. In the same way as described in chapter 2 and the second variant in chapter 5, cultural adaptation takes place.