Modeling Social Information in Conflict Situations through Instance-Based Learning Theory

Modeling Social Information in Conflict Situations through Instance-Based Learning Theory Varun Dutt, Jolie M. Martin, Cleotilde Gonzalez varundutt@cmu.edu, jolie@cmu.edu, coty@cmu.edu Dynamic Decision Making Laboratory, Carnegie Mellon University 4609 Winthrop Street, Pittsburgh, PA 15213 Abstract: Behavior in conflict situations can be influenced by the social information that individuals have about their opponents. This paper tests whether an existent Instance-based Learning (IBL) model, built using the Instance-based Learning Theory (IBLT) to explain behavior in a single-person binary-choice task (BCT), can predict behavior in a two-player iterated prisoner’s dilemma (IPD) game. The same IBL model is generalized to two conditions in the IPD: Social, where individuals have information about their opponents and their choices; and Non-social, where individuals and opponents lack this information. We expect the single-person IBL model to predict behavior in the Non-social condition better than in the Social condition. However, due to the structural differences between BCT and IPD, we also expect only moderately good model predictions in the Non-social condition. Our results confirm these expectations. These findings highlight the need for additional cognitive mechanisms to account for social information in conflict situations. Keywords: conflict; cooperation; social information; 2x2 games; iterated prisoner’s dilemma; instance-based learning theory; cognitive modeling; generalization. Introduction One objective of a participant in 2x2 games (between two players, each of whom has two available choice options), is to maximize personal economic benefit by cooperating or competing with an opponent. A popular game called the prisoner's dilemma (PD) (Axelrod, 1980; Rapoport & Chammah, 1965) has been widely used to investigate such conflict situations. In the PD, each of two participants chooses simultaneously whether to cooperate (C) or defect (D). If both cooperate, they obtain an equal outcome that is larger than if both had chosen to defect. (In Figure 1, each player’s outcomes are higher for C-C than for D-D.) Figure 1. The matrix of outcomes in the prisoner’s dilemma game. “Your Action” and “Opponent’s Action” refer to the actions of the two players. “D” and “C” are labels used for “defection” and “cooperation,” respectively. However, if one participant defects while the other cooperates, the defector obtains an even larger outcome while the cooperator suffers a loss (shown by the C-D and D-C outcomes in Figure 1). In a one-trial PD, the standard finding is a larger proportion of D choices than C choices when aggregated over several participants (Rapoport & Chammah, 1965). However, in the iterated PD (IPD), where people are asked to repeatedly make C or D decisions, the proportion of D choices are shown to decrease over time (Rapoport & Chammah, 1965). Thus, the PD represents a tradeoff between short-term individual gain of defection and long-term individual gain of sustained mutual cooperation (Baker & Rachlin, 2002). Despite the general focus on maximizing personal benefits in the PD, researchers have argued that the economic perspective alone is oftentimes insufficient to capture the social aspects of such games, including the amount of information that is shared between participants (Dawes, Van De Kragt, & Orbell, 1988; Gonzalez & Martin, 2011; Schuster & Perelberg, 2004). For example, if a participant does not know that he is actually playing with another human opponent in the IPD, is not provided with the matrix in Figure 1, and is asked to maximize his benefits by repeatedly choosing between the C and D buttons from experience (Non-social condition), then he might strive to strictly maximize his own observed outcomes. However, when the participant knows that he is playing a human opponent and has descriptive information about how his own and opponent’s choices will affect one another’s outcomes (e.g., Figure 1) (Social condition), he might be inclined to take the other’s perspective. In the Social condition, he chooses to cooperate or defect not only to maximize his own outcomes, but also to uphold his preferences regarding fairness and trust (Baker & Rachlin, 2002; Gonzalez & Martin, 2011). Furthermore, recent literature in decisions from experience has shown that human behavior is primarily driven by experience when people are presented with both the descriptive and experiential information (like that in the Social condition in the form of knowledge of human opponents and outcomes in Figure 1 along with repeated