Information Acquisition in the Iterated Prisoner's Dilemma Game: An Eye-Tracking Study

Information Acquisition in the Iterated Prisoner’s Dilemma Game: An Eye-Tracking Study Evgenia Hristova (ehristova@cogs.nbu.bg ) Central and Eastern European Center for Cognitive Science, New Bulgarian University, 21, Montevideo street, Sofia 1618, Bulgaria Maurice Grinberg (mgrinberg@nbu.bg) Central and Eastern European Center for Cognitive Science, New Bulgarian University, 21, Montevideo street, Sofia 1618, Bulgaria The bounded rationality theoretical framework (see e.g. Simon, 1955), implies limitations on cognition and states that people devote limited efforts in making decisions. Computations are cognitively expensive and people usually try to avoid them. According to these theories, rationality should be replaced by a behavior compatible with limited access to information and limited computational capacity (Simon, 1955; Einhorn & Hogarth, 1981). Playing PD games surely demands a considerable cognitive effort. To grasp the whole structure of the game, the player should pay attention not only to his payoffs but also to take into account the possible payoffs of the other player. What’s more, the game outcome for the player depends not only on her moves but also on the moves of the opponent. Form the bounded rationality standpoint, we can hypothesize that, in the case of PD, subjects are also using only a limited portion of the available information and are not reasoning much ahead about their opponent’s moves. Although suboptimal, with regard to the game theoretical reasoning, such a behavior requires less cognitive resources and seems much more plausible to take place in reality. This brief discussion shows how important the detailed investigation of the information processing is in order to understand the specific judgment and decision making processes that take place in game playing. In the present paper, we study the typical patterns of information acquisition in PD games by recording eye movements. This is an attempt to reveal the actual cognitive processes involved in playing and to explore the way in which subjects make use of various characteristics of the game (like the cooperation index). As established in previous experiments (Hristova & Grinberg, 2004), different groups of subjects can be identified depending on their predominant cooperation patterns. Here, we want to further explore the differences between these groups by analyzing the specificity of their information acquisition strategies as evidenced by the eye-tracking technique. Abstract Eye-tracking recordings were used to explore the choice process in playing the iterated Prisoner’s dilemma. This is a novel approach in studying the cognitive processes in game playing. The information acquisition patterns of two groups of subjects, identified on the basis of their playing behavior, were compared. The subjects from the first group paid more attention to the game payoffs and showed a strong dependence on their relative magnitudes. The subjects from the second group paid less attention to the payoff matrix but spent more time considering the opponent moves. These results show that the analysis of eye movement can give valuable information about the processes of decision making. Keywords: eye-tracking; information aquisition. prisoner’s dillema game; Introduction The iterated Prisoner’s Dilemma (PD) game has been widely used as a model for exploring the determinants of cooperative behavior in social situations. The PD game has attracted much attention in the scientific literature and considerable numbers of papers have appeared (e.g. Rapoport & Chammah, 1965; Rapoport & Mowshowitz, 1966 and more recently Camerer & Ho, 2002; Erev & Roth, 2001; Macy & Flache, 2002). However, no considerable efforts were invested in the careful study of the cognitive processes involved in playing the PD game. For instance, questions like what are the specific patterns of information acquisition about the game and how they are related to the behaviour observed (like the dependence of the moves on the so-called cooperation index, Rapoport & Chammah, 1965) remain open. One of the strong assumptions in the formal game theory is that the players have complete knowledge about the game, the possible strategies and payoffs (Colman, 2003). The psychological game theory and behavioural game theory are expected to provide better predictions of experimental observations (Colman, 2003; Camerer, 2003). They are based on experimentally determined psychological regularities and seem to give more accurate explanations than traditional game theory. The Prisoner’s Dilemma Game Prisoner’s dilemma is a two-person game. The payoff table for this game is presented in Figure 1. The players simultaneously choose their move – C (cooperate) or D (defect), without knowing their opponent’s choice.