Reward sensitivity and anger in euthymic bipolar disorder

According to the hypersensitive behavioral approach system (BAS) model of bipolar disorder (BP), hypersensitivity of the BAS is a trait that should be present even in the euthymic state. This would be expected to result in increased anger and reward sensitivity, both of which are related to the approach system. This study examined these predictions through the use of tasks that assess different aspects of the BAS: reward sensitivity, anger and impulsivity. These characteristics were assessed using the probabilistic classification task (PCT), ultimatum game (UG) and single key impulsivity paradigm (SKIP), respectively. Participants were euthymic adult bipolar disorder patients (BP; N=40) and healthy controls (HC; N=41). In the UG, all participants showed the standard pattern of rejecting overtly unfair offers and accepting clearly fair offers; however, BPs rejected more of the moderately unfair offers than did HCs. BP and HC participants did not differ on their ability to learn, but did show different patterns of learning from reward and punishment. Learning for reward and punishment were negatively correlated in the BP group, suggesting that individuals could learn well either from reward or punishment, but not both. No correlation was found between these forms of learning in the HC group. BP patients show signs of their disorder even in the euthymic state, as seen by the dysbalance between reward and punishment learning and their residual anger in the UG.     

The neural basis for establishing a focal point in pure coordination games

When making a decision, humans often have to ‘coordinate’—reach the same conclusion—as another individual without explicitly communicating. Relatively, little is known about the neural basis for coordination. Moreover, previous fMRI investigations have supported conflicting hypotheses. One account proposes that individuals coordinate using a ‘gut feeling’ and that this is supported by insula recruitment. Another account proposes that individuals recruit strategic decision-making mechanisms in prefrontal cortex in order to coordinate. We investigate the neural basis for coordination in individuals with behavioral-variant frontotemporal dementia (bvFTD) who have limitations in social decision-making associated with disease in prefrontal cortex. We demonstrate that bvFTD are impaired at establishing a focal point in a semantic task (e.g. ‘Tell me any boy''s name’) that requires coordination relative to a similar, control semantic task that does not. Additionally, coordination limitations in bvFTD are related to cortical thinning in prefrontal cortex. These findings are consistent with behavioral economic models proposing that, beyond a ‘gut feeling’, strategic decision-making contributes to the coordination process, including a probabilistic mechanism that evaluates the salience of a response (e.g. is ‘John’ a frequent boy''s name), a hierarchical mechanism that iteratively models an opponent''s likely response and a mechanism involved in social perspective taking.     

A young people's perspective on computer game addiction

In this article, I examine computer game addiction as a social phenomenon, analyzing the consequences of using the term in order to express a concern about high frequency consumption or even a problematic usage of computer games. I argue that while it is obviously very important to take seriously these concerns about young people “at risk,” there is a gap between the phenomenon as a suggested psychiatric diagnosis and young people's reflections on the matter. Following the work of Goffman and Becker, computer game addiction is not necessarily something negative in the eyes of the player and other young people. It is shown that the classification can be a positive element in young people's identity work. On the other hand, a high consumption of computer games is also considered as “culturally unacceptable.” From this perspective, computer game addiction becomes a question of how to construct the boundaries between normality and deviance and how prejudices are governing and controlling young people's lives. All this suggests more caution in classifying frequent and problematic computer game play as a disorder in itself. We need a more complex understanding of computer game addiction than research so far has offered us.     

The temporal course of the influence of anxiety on fairness considerations

This study investigated the potential causes of anxious people's social avoidance. The classic ultimatum game was utilized in concert with electroencephalogram recording. Participants were divided into two groups according to levels of trait anxiety as identified by a self‐report scale. The behavioral results indicate that high‐anxious participants were more prone to reject human‐proposed than computer‐proposed unequal offers compared to their low‐anxious counterparts. The event‐related potential results indicate that the high‐anxious group showed a larger feedback‐related negativity when receiving unequal monetary offers than equal ones, and a larger P3 when receiving human‐proposed offers than computer‐proposed ones, but these effects were absent in the low‐anxious group. We suggest anxious people's social avoidance results from hypersensitivity to unequal distributions during interpersonal interactions.     

Collapse of cooperation in evolving games

Game theory provides a quantitative framework for analyzing the behavior of rational agents. The Iterated Prisoner’s Dilemma in particular has become a standard model for studying cooperation and cheating, with cooperation often emerging as a robust outcome in evolving populations. Here we extend evolutionary game theory by allowing players’ payoffs as well as their strategies to evolve in response to selection on heritable mutations. In nature, many organisms engage in mutually beneficial interactions and individuals may seek to change the ratio of risk to reward for cooperation by altering the resources they commit to cooperative interactions. To study this, we construct a general framework for the coevolution of strategies and payoffs in arbitrary iterated games. We show that, when there is a tradeoff between the benefits and costs of cooperation, coevolution often leads to a dramatic loss of cooperation in the Iterated Prisoner’s Dilemma. The collapse of cooperation is so extreme that the average payoff in a population can decline even as the potential reward for mutual cooperation increases. Depending upon the form of tradeoffs, evolution may even move away from the Iterated Prisoner’s Dilemma game altogether. Our work offers a new perspective on the Prisoner’s Dilemma and its predictions for cooperation in natural populations; and it provides a general framework to understand the coevolution of strategies and payoffs in iterated interactions.Iterated games provide a framework for studying social interactions (1–6) that allows researchers to address pervasive biological problems such as the evolution of cooperation and cheating (2, 7–12). Simple examples such as the Iterated Prisoner’s Dilemma, Snowdrift, and Stag Hunt games (13–18) showcase a startling array of counterintuitive social behaviors, especially when studied in a population replicating under natural selection (16, 19–25). Despite the subject’s long history, a systematic treatment of all evolutionary robust cooperative outcomes for even the simple Iterated Prisoner’s Dilemma has only recently emerged (21, 26–29).Understanding the evolution of strategies in a population under fixed payoffs already poses a steep challenge. To complicate matters further, in many biological settings the payoffs themselves may also depend on the genotypes of the players. Changes to the payoff matrix have been studied in a number of contexts, including one-shot two-player games (13), payoff evolution without strategy evolution (30, 31), under environmental “shocks” to the payoff matrix (32–34), and using continuous games (22, 23, 35). Here we adopt a different approach, and we explicitly study the coevolutionary dynamics between strategies and payoffs in iterated two-player games. We decouple strategy mutations from payoff mutations, and we leverage results on the evolutionary robustness of memory-1 strategies with arbitrary payoff matrices to explore the relationship between payoff evolution and the prevalence of cooperation in a population. We identify a feedback between the costs and benefits of cooperation and the evolutionary robustness of cooperative strategies. Depending on the functional form (35) of the relationship between costs and benefits, this feedback may either reinforce the evolutionary success of cooperation or else precipitate its collapse. In particular, we show that cooperation will always collapse when there are diminishing returns for mutual cooperation.     

Teaching Geriatrics Using an Innovative,Individual‐Centered Educational Game: Students and Educators Win. A Proof‐of‐Concept Study

Given the increasingly aging population, nearly every doctor will encounter elderly adults who present with multiple complex comorbidities that can challenge even experienced physicians. This may explain why many medical students do not have a positive attitude toward elderly adults and find the complexity of their problems overwhelming. It was hypothesized that a recently developed medical school geriatrics course, based on the game GeriatriX and designed specifically to address the complexities associated with decision‐making in geriatrics, can have a positive effect on attitudes toward geriatrics and on perceived knowledge of geriatrics. The effects of this game‐based course were evaluated as a proof of concept. The assessment was based on the Aging Semantic Differential (ASD) and a validated self‐perceived knowledge scale of geriatric topics. The usability of (and satisfaction with) GeriatriX was also assessed using a 5‐point Likert scale. After completion of the course, the ASD changed significantly in the geriatrics course group (n = 29; P = .02) but not in a control group that took a neuroscience course (n = 24; P = .30). Moreover, the geriatrics course group had a significant increase in self‐perceived knowledge for 12 of the 18 topics (P = .002), whereas in the control group self‐perceived knowledge increased significantly for one topic only (sensory impairment) (P = .04). Finally, the geriatrics students reported enjoying GeriatriX. This proof‐of‐concept study clearly supports the hypothesis that a 4‐week course using a modern educational approach such as GeriatriX can improve students' self‐perceived knowledge of geriatrics and their attitudes toward elderly adults.     

Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma

It is not fully understood why we cooperate with strangers on a daily basis. In an increasingly global world, where interaction networks and relationships between individuals are becoming more complex, different hypotheses have been put forward to explain the foundations of human cooperation on a large scale and to account for the true motivations that are behind this phenomenon. In this context, population structure has been suggested to foster cooperation in social dilemmas, but theoretical studies of this mechanism have yielded contradictory results so far; additionally, the issue lacks a proper experimental test in large systems. We have performed the largest experiments to date with humans playing a spatial Prisoner's Dilemma on a lattice and a scale-free network (1,229 subjects). We observed that the level of cooperation reached in both networks is the same, comparable with the level of cooperation of smaller networks or unstructured populations. We have also found that subjects respond to the cooperation that they observe in a reciprocal manner, being more likely to cooperate if, in the previous round, many of their neighbors and themselves did so, which implies that humans do not consider neighbors' payoffs when making their decisions in this dilemma but only their actions. Our results, which are in agreement with recent theoretical predictions based on this behavioral rule, suggest that population structure has little relevance as a cooperation promoter or inhibitor among humans.     

Iterated Prisoner's Dilemma contains strategies that dominate any evolutionary opponent

The two-player Iterated Prisoner's Dilemma game is a model for both sentient and evolutionary behaviors, especially including the emergence of cooperation. It is generally assumed that there exists no simple ultimatum strategy whereby one player can enforce a unilateral claim to an unfair share of rewards. Here, we show that such strategies unexpectedly do exist. In particular, a player X who is witting of these strategies can (i) deterministically set her opponent Y's score, independently of his strategy or response, or (ii) enforce an extortionate linear relation between her and his scores. Against such a player, an evolutionary player's best response is to accede to the extortion. Only a player with a theory of mind about his opponent can do better, in which case Iterated Prisoner's Dilemma is an Ultimatum Game.     

Fairness concerns predict medial frontal negativity amplitude in ultimatum bargaining

Abstract

Despite evidence that anterior cingulate cortex (ACC) activity is related to social exclusion, rejection and unfairness, evidence that medial frontal negativity (MFN), which has its source in the ACC, reflects these constructs remains unforthcoming. In the present study, subjects participated as recipients in an ultimatum game, while we recorded their electro-encephalogram (EEG). Participants responded to fair and unfair offers from different human proposers. In addition, participants rated themselves on a measure evaluating their concern for fairness. Results showed that MFN amplitude was more pronounced for unfair offers compared to fair offers. Moreover, this effect was shown to be most pronounced for subjects with high concerns for fairness. Our findings suggest that the MFN not only reflects whether outcomes match expectations, but also reflects whether the process by which these outcomes came about matches a social or even a moral norm. In addition, the present results suggest that people in bargaining situations are not only concerned with their own outcomes, but are also concerned with the fairness of the process that resulted in these outcomes.     

Nash equilibrium solutions of tracking game for bilinear systems with exponential reference signals

In this paper, we consider the problem of Nash equilibrium solutions of two players tracking game for bilinear systems. A successive approximation approach is modified to design optimal controllers for bilinear systems. More specifically, a sequence of extended Sylvester differential equations are solved by this modified approach. A simulation example is given to demonstrate the validity of this approach. Copyright © 2012 John Wiley & Sons, Ltd.