1 Toward a unified theory of learned trust.
Juvina, I., Collins, M., Larue, O., & de Melo, C., International Conference on Cognitive Modeling (ICCM 16), 2016
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A proposal for a unified theory of learned trust is presented. A number of limitations of a published computational cognitive model of learned trust are discussed. A solution is proposed to overcome these limitations and expand the model’s scope of applicability. The revised model integrates several seemingly unrelated categories of findings from the literature and makes unintuitive predictions for future studies. The implications of the model for the advancement of the theory on trust are discussed.

2 Neurophysiological effects of negotiation framing
Khooshabeh, P., Lin, R., de Melo, C., Gratch, J., Ouimette, B., et al., Annual Meeting of the Cognitive Science Society (CogSci 16), 2016
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In this study, we manipulated gain/loss framing context during a simulated negotiation between a human user and a virtual agent. Task instructions placed users either in a loss or gain framed context, such that those in the loss frame had to minimize expenses whereas those in the gain frame had to maximize profits. The virtual agent displayed facial emotions so that we could also test how interpersonal emotions interact with framing. Results suggest that individuals are more motivated to minimize their losses than maximizing their gains. The loss frame caused individuals to demand more during the negotiation, hence to minimize expenses. Neurophysiological results suggest that cardiovascular patterns of challenge (i.e., positive motivations) were present in the loss frame condition, most strongly when the virtual human smiled. We discuss these results in regards to Prospect Theory. This work also has implications for designing and rigorously evaluating humanlike virtual agents.

3. Bridging the gap between human and non-human decision makers.
de Melo, C., Carnevale, P., & Gratch, J., Annual Meeting of International Association for Conflict Management (IACM 14), 2014
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4. Social categorization and cooperation between humans and computers.
de Melo, C., Carnevale, P., & Gratch, J., Annual Meeting of the Cognitive Science Society (CogSci 14), 2014
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5 Agent or avatar? Using virtual confederates in conflict management research.
de Melo, C., Carnevale, P., & Gratch, J., Annual Meeting of the Academy of Management (AOM 13), 2013
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Virtual confederates–i.e., three-dimensional virtual characters that look and act like humans–are used in a growing number of empirical studies, especially in the behavioral and medical sciences. The growing popularity of this research method stems from increased experimental control, ease of replication, facilitated access to broader samples and lower costs. In this paper we investigate the plausibility of virtual confederates for conducting research in conflict management. We posit that generality studies that compare findings with human and virtual confederates are required to determine the merits of virtual confederates. To accomplish this we present two novel studies where people engaged in a social dilemma (Experiment 1) and in a negotiation (Experiment 2) with virtual confederates that expressed emotions in their faces. Experiment 1 showed that people cooperated more with a virtual confederate that showed cooperative displays (e.g., smile in mutual cooperation) than one that showed competitive displays (e.g., smile after exploiting the participant). Experiment 2 showed that people conceded more to an angry virtual confederate than to a neutral one. These results comport with previous findings from similar studies with humans thus supporting the viability of virtual confederates as a research tool. Our results also reveal that virtual confederates are more successful in achieving social influence when participants are convinced that humans control the virtual images (i.e., the confederate is an avatar), rather than computer programs (i.e., the confederate is an agent). We discuss implications for research in conflict management.

6 Cooperative strategies with incongruent facial expressions cause cardiovascular threat.
Khooshabeh, P., de Melo, C., Volkman, B., Gratch, J., Blascovich, J., & Carnevale, P., Annual Meeting of the Cognitive Society (CogSci 13), 2013
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Affect is important in motivated performance situations such as negotiation. Longstanding theories of emotion suggest that facial expressions provide enough information to perceive another person's internal affective state. Alternatively, the contextual emotion hypothesis posits that situational factors bias the perception of emotion in others' facial displays. This hypothesis predicts that individuals will have different perceptions of the same facial expression depending upon the context in which the expression is displayed. In this study, cardiovascular indexes of motivational states (i.e., challenge vs. threat) were recorded while players engaged in a multiissue negotiation where the opposing negotiator (confederate) displayed emotional facial expressions (angry vs. happy}, the confederate's negotiation strategy (cooperative vs. competitive) was factorially crossed with his facial expression. During the game, participants' eye fixations and cardiovascular responses, indexing task engagement and challenge/threat motivation, were recorded. Results indicated that participants playing confederates with incongruent facial expressions (e.g., cooperative strategy, angry face) exhibited a greater threat response, which arises due to increased uncertainty. Eye fixations also suggest that participants look at the face more in order to acquire information to reconcile their uncertainty in the incongruent condition. Taken together, these results suggest that context matters in the perception of emotion.

7 People's biased decisions to trust and cooperate with agents that express emotions.
de Melo, C., Carnevale, P., & Gratch, J., Trust Workshop at the Autonomous Agents and Multiagent Systems (AAMAS) Conference, 2013
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Research in the behavioral sciences shows that emotion expressions impact people's decisions to trust and cooperate with others in situations where self and collective interests collide. Building on such findings, computer scientists have shown that emotion expressions in agents can also impact people's decision making. However, recent findings in neuroeconomics reveal that people systematically show different behavior and brain activation patterns in decision making tasks with computers, when compared to humans. These findings suggest a bias people might have with respect to autonomous agents and, in particular, agents that express emotions. To clarify this, the paper presents a novel experiment where participants engaged in the iterated prisoner's dilemma, for clear financial stakes, with counterparts, either agents or humans, that showed facial displays of emotion that were compatible with a cooperative (e.g., smile after mutual cooperation) or competitive (e.g., smile after exploiting the participant) goal orientation. The results showed that participants cooperated, as expected, more with cooperative than competitive counterparts but, also revealed that people trusted and cooperated more with a human that showed cooperative displays than an agent that showed the exact same displays. We discuss implications of such a bias for trust and cooperation in human-agent interaction.

8 Reverse appraisal: The importance of appraisals for the effect of emotion displays on people's decision-making in a social dilemma.
de Melo, C., Carnevale, P., Read, S., & Gratch, J., Annual Meeting of the Cognitive Science Society (CogSci 12), 2012
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Two studies are presented that explore the interpersonal effect of emotion displays in decision making in a social dilemma. Experiment 1 (N=405) showed that facial displays of emotion (joy, sadness, anger and guilt) had an effect on perception of how the person was appraising the social dilemma outcomes (perception of appraisals) and on perception of how likely the person was to cooperate in the future (perception of cooperation). Experiment 1 also showed that perception of appraisals (partially and, in some cases, fully) mediated the effect of emotion displays on perception of cooperation. Experiment 2 (N=202) showed that manipulating perception of appraisals, by expressing them textually, produced an effect on perception of cooperation thus, providing evidence for a causal model where emotion displays cause perception of appraisals which, in turn, cause perception of cooperation. In line with Hareli and Hess' (2010) findings and a social-functions view of emotion, we advance the reverse appraisal proposal that argues people can infer, from emotion displays, how others are appraising a situation which, in turn, support inferences that are relevant for decision making. We discuss implications of these results and proposal to decision and emotion theory.

9 Reverse appraisal: Inferring from emotion displays who is the cooperator and the competitor in a social dilemma.
de Melo, C., Carnevale, P., & Gratch, J., Annual Meeting of the Cognitive Science Society (CogSci 11), 2011
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This paper explores whether and how facial displays of emotion can impact emergence of cooperation in a social dilemma. Three experiments are described where participants play the iterated prisoner's dilemma with (computer) players that display emotion. Experiment 1 compares a cooperative player, whose displays reflect a goal of mutual cooperation, with a control player that shows no emotion. Experiment 2 compares a competitive player, whose displays reflect a goal of getting more points than the participant, and the control player. Experiment 3 compares the cooperative and competitive players. Results show that people: cooperate more with the cooperative than the control player (Experiment 1}, do not cooperate differently with the competitive and control players (Experiment 2}, and, cooperate more with the cooperative than the competitive player, when they play the latter first (Experiment 3). In line with a social functions view of emotion, we argue people infer, from emotion displays, the other player's propensity to cooperate by reversing the emotion appraisal process. Post-game surveys show that people interpret the emotion displays according to appraisal variables (desirability, responsibility and controllability) in ways that are consistent with predictions from appraisal theories of emotion.

10 These are ours: The effects of ownership and groups on property negotiation.
Carnevale, P., Kim, Y., de Melo, C., Dehghani, M., & Gratch, J., Annual Conference of the International Association for Conflict Management (IACM 11), 2011
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Ownership tends to affect negotiation by increasing the value that the negotiator places on the objects being negotiated. In this study, we invented a new computer-controlled negotiation task that presents negotiators pictures of objects on a screen and the negotiators grab the objects, or give them to an opponent, using a mouse. We experimentally varied ownership, telling negotiators in one case that they owned the objects (but needed the other's agreement on the distribution of the objects), or the other owned the objects (but their agreement was needed for distribution), or neither party owned the objects (and both had to agree on the distribution). We also varied whether negotiations were conducted by 3-person groups, or by individuals, and we varied the opponent's behavior in the negotiation (the other consistently demanded almost all the objects, hardly demanded any, or was totally responsive with a Tit-for-Tat strategy on the objects). We also varied the value of the objects, thus giving the task an integrative structure. One result was that groups were more likely than individuals to match the opponent's competitiveness, but only when ownership of the objects was undefined. Ownership, either self, or other, attenuated differences between groups and individuals, an effect not observable in studies that use abstract negotiation tasks or prisoner-dilemma–type games.