For each round of the game, the model checks whether it has previously
encountered the same situation, and if so, what action (decision) it took in that
situation. The situation is characterized by the choices of all the players and the group
choices in the previous round. For example, let us assume that the current state of the
game is the one represented in Table 2, where the human player is substituted by the
model. We see that in the previous round the model played B, its group mate played
A, and the two players on the opposite group played B (where A and B were
randomly assigned to cooperate and defect, respectively). The group choice was B for
both groups. This information constitutes the situation components of the instance.
These attributes will act as the retrieval cues: the model will attempt to remember
whether an identical situation has previously been encountered. The model’s memory
stores as an instance each situation that is encountered at each round of the game and
the associated decision taken by the model in that situation.