1569868067 1 Abstract— To understand the processes involved in trust-based judgments in a computer-mediated multi-agent setting, a user interface (UI) was developed and an experiment was devised based on the Iterated Diner’s Dilemma, a variation of the n- player Prisoner’s Dilemma. Analysis of the experiment resulted in two major findings: (1) UI composition and information presentation have an impact on human trust and cooperation behavior, and (2) a strong positive correlation between Situation Awareness (SA) and performance is confirmed. There was a significant effect for UI levels on our main performance metric, total participant dining points, at the p=0.041 level. Also, there was a marginal effect for UI levels on participant cooperation at the p=0.084 level. Total participant dining points and SA were strongly correlated, r (92) = 0.62. Similarly, participant cooperation and SA were strongly correlated, r (92) = 0.61. Index Terms—User interface, composite network, trust, trust- based judgment, Diner’s Dilemma, Situation Awareness, human behavior I. INTRODUCTION N TODAY’S highly networked world, an increasing number of decisions are made in online settings. In many cases, these decisions involve collaborative discussion, on-the-fly analysis of shared data, and various other interactions through computer-mediated collaboration platforms. Online users’ perception of the available information is by necessity influenced by the tools and user interfaces that provide them access to the data and enable interactive analysis. The impact of user interface (UI) components on online decision-making behavior in terms of trust, cooperation and participants’ awareness of the situation surrounding a decision is investigated in detail in this paper. The contexts of online decisions are diverse and difficult to This manuscript was received on November 17, 2013. This material is based in part upon work supported by the U.S. Army Research Laboratory under Cooperative Agreement No. W911NF-09-2-0053 and by NSF grant IIS- 1058132. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory, NSF, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes not-with-standing any copyright notation here on. model in a comprehensive way. In this experiment, a representative abstract decision-making game, known as the Iterative Diner’s Dilemma (DD), is employed and theoretical and experimental analysis are applied to explore the complex role of the UI in the involved decision making. DD is an n- player version of the well-known Prisoner's Dilemma that has been extensively studied over the years [2, 14, 20, 21]. The scenario is that several individuals go out to eat with a prior agreement to share the bill equally, with the understanding that the same group of people will repeat these dining dates an unspecified number of times in the future. On each occasion, each diner chooses whether to order an expensive or inexpensive dish, knowing that the bill will be shared equally by all diners. To measure participants’ awareness of the rules and progress of the abstract game, the concept and theory of situation awareness (SA) [8] was used. Endsley defines SA as a person's "perception of the elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future." In a large variety of contexts SA has been recognized as key to successful decision making and performance at the individual and team levels [9, 27]. Few research papers were found that reported an empirical test of the role of SA and UI support in trust-based judgments in a Prisoner's Dilemma-like setting. This experiment builds on and significantly extends previously reported work on DD and different UI levels for following game progress [30] (cf. detailed discussion in Section II B). To study the effects of UI components on awareness and decision-making behavior, an online study of 95 users was conducted using Amazon’s Mechanical Turk (MTurk). Participants played repeated trials of the DD game, and answered evaluative questionnaires at multiple stages in the game. We were interested in potential correlations of SA and human performance; in the design of UI elements (Fig. 1) to improve SA, interpersonal trust (cooperation), and performance; and finally in the characterization and ultimately modeling of observed human behavior. The experiment highlights two key effects. First, there is a strong correlation between SA and performance in the game, and second, UI composition and information presentation have an impact on Decision-making in Abstract Trust Games: A User Interface Perspective Emrah Onal 1 , James Schaffer 2 , John O’Donovan 2 , Laura R. Marusich 3 , Michael S. Yu 4 , Cleotilde Gonzalez 4 , Tobias Höllerer 2 1 SA Technologies 2 Department of Computer Science, University of California, Santa Barbara 3 Human Research and Engineering Directorate, U.S. Army Research Laboratory 4 Department of Social and Decision Sciences, Carnegie Mellon University I