Growth and inequality in public good provision

In a novel experimental design we study public good games with dynamic interdependencies, where each agent’s wealth at the end of period t serves as her endowment in t + 1. In this setting growth and inequality arise endogenously allowing us to address new questions regarding their interplay and effect on cooperation. We find that amounts contributed are increasing over time even in the absence of punishment possibilities. Variation in wealth is substantial with the richest groups earning more than ten times what the poorest groups earn. Introducing the possibility of punishment does not increase wealth and in some cases even decreases it. In the presence of a punishment option inequality in early periods is strongly negatively correlated with group income in later periods, highlighting negative interaction effects between endogenous inequality and punishment

Natural disasters and indicators of social cohesion

Do adversarial environmental conditions create social cohesion? We provide new answers to this question by exploiting spatial and temporal variation in exposure to earthquakes across Chile. Using a variety of methods and controlling for a number of socio-economic variables, we find that exposure to earthquakes has a positive effect on several indicators of social cohesion. Social cohesion increases after a big earthquake and slowly erodes in periods where environmental conditions are less adverse. Our results contribute to the current debate on whether and how environmental conditions shape formal and informal institutions

The neural circuitry of emotion-induced distortions of trust

Aversive emotions are likely to be a key source of irrational human decision-making but still little is known about the underlying neural circuitry. Here, we show that aversive emotions distort trust decisions and cause significant changes in the associated neural circuitry. They reduce trust and suppress trust-specific activity in left temporoparietal junction (TPJ). In addition, aversive emotions reduce the functional connectivity between TPJ and emotion-related regions such as the amygdala. We also find that the posterior superior temporal sulcus (pSTS) plays a key role in mediating the impact of aversive emotions on brain-behavior relationships. Functional connectivity of right pSTS with left TPJ not only predicts mean trust taking in the absence of negative emotions, but aversive emotions also largely remove this association between TPJ-pSTS connectivity and behavioral trust. These findings may be useful for a better understanding of the neural circuitry of affective distortions and may thus help identify the neural bases of psychiatric diseases that are associated with emotion-related psychological and behavioral dysfunctions

The neural circuitry of affect-induced distortions of trust

Aversive affect is likely a key source of irrational human decision-making, but still, little is known about the neural circuitry underlying emotion-cognition interactions during social behavior. We induced incidental aversive affect via prolonged periods of threat of shock, while 41 healthy participants made investment decisions concerning another person or a lottery. Negative affect reduced trust, suppressed trust-specific activity in the left temporoparietal junction (TPJ), and reduced functional connectivity between the TPJ and emotion-related regions such as the amygdala. The posterior superior temporal sulcus (pSTS) seems to play a key role in mediating the impact of affect on behavior: Functional connectivity of this brain area with left TPJ was associated with trust in the absence of negative affect, but aversive affect disrupted this association between TPJ-pSTS connectivity and behavioral trust. Our findings may be useful for a better understanding of the neural circuitry of affective distortions in healthy and pathological populations

The neural circuitry of affect-induced distortions of trust

Aversive affect is likely a key source of irrational human decision-making, but still, little is known about the neural circuitry underlying emotion-cognition interactions during social behavior. We induced incidental aversive affect via prolonged periods of threat of shock, while 41 healthy participants made investment decisions concerning another person or a lottery. Negative affect reduced trust, suppressed trust-specific activity in the left temporoparietal junction (TPJ), and reduced functional connectivity between the TPJ and emotion-related regions such as the amygdala. The posterior superior temporal sulcus (pSTS) seems to play a key role in mediating the impact of affect on behavior: Functional connectivity of this brain area with left TPJ was associated with trust in the absence of negative affect, but aversive affect disrupted this association between TPJ-pSTS connectivity and behavioral trust. Our findings may be useful for a better understanding of the neural circuitry of affective distortions in healthy and pathological populations

Anticipatory Anxiety Disrupts Neural Valuation during Risky Choice

Incidental negative emotions unrelated to the current task, such as background anxiety, can strongly influence decisions. This is most evident in psychiatric disorders associated with generalized emotional disturbances. However, the neural mechanisms by which incidental emotions may affect choices remain poorly understood. Here we study the effects of incidental anxiety on human risky decision making, focusing on both behavioral preferences and their underlying neural processes. Although observable choices remained stable across affective contexts with high and low incidental anxiety, we found a clear change in neural valuation signals: during high incidental anxiety, activity in ventromedial prefrontal cortex and ventral striatum showed a marked reduction in (1) neural coding of the expected subjective value (ESV) of risky options, (2) prediction of observed choices, (3) functional coupling with other areas of the valuation system, and (4) baseline activity. At the same time, activity in the anterior insula showed an increase in coding the negative ESV of risky lotteries, and this neural activity predicted whether the risky lotteries would be rejected. This pattern of results suggests that incidental anxiety can shift the focus of neural valuation from possible positive consequences to anticipated negative consequences of choice options. Moreover, our findings show that these changes in neural value coding can occur in the absence of changes in overt behavior. This suggest a possible pathway by which background anxiety may lead to the development of chronic reward desensitization and a maladaptive focus on negative cognitions, as prevalent in affective and anxiety disorders

Anticipatory anxiety disrupts neural valuation during risky choice

Incidental negative emotions unrelated to the current task, such as background anxiety, can strongly influence decisions. This is most evident in psychiatric disorders associated with generalized emotional disturbances. However, the neural mechanisms by which incidental emotions may affect choices remain poorly understood. Here we study the effects of incidental anxiety on human risky decision making, focusing on both behavioral preferences and their underlying neural processes. Although observable choices remained stable across affective contexts with high and low incidental anxiety, we found a clear change in neural valuation signals: during high incidental anxiety, activity in ventromedial prefrontal cortex and ventral striatum showed a marked reduction in (1) neural coding of the expected subjective value (ESV) of risky options, (2) prediction of observed choices, (3) functional coupling with other areas of the valuation system, and (4) baseline activity. At the same time, activity in the anterior insula showed an increase in coding the negative ESV of risky lotteries, and this neural activity predicted whether the risky lotteries would be rejected. This pattern of results suggests that incidental anxiety can shift the focus of neural valuation from possible positive consequences to anticipated negative consequences of choice options. Moreover, our findings show that these changes in neural value coding can occur in the absence of changes in overt behavior. This suggest a possible pathway by which background anxiety may lead to the development of chronic reward desensitization and a maladaptive focus on negative cognitions, as prevalent in affective and anxiety disorders

Nanofibrous scaffolds releasing a small molecule BDNF-mimetic for the re-direction of endogenous neuroblast migration in the brain

9siBrain tissue engineering has the potential to harness existing elements of neurogenesis within the adult brain to overcome a microenvironment that is otherwise inhibitory to regeneration, especially following severe tissue damage. This study investigates the ability of electrospun poly ε-caprolactone (PCL) to re-direct the migratory pathway of endogenous neuroblasts from the disrupted subventricular zone (SVZ). A small molecule non-peptide ligand (BDNF-mimetic) that mimicked the trophic properties of brain-derived neurotrophic factor (BDNF) was incorporated into electrospun PCL scaffolds to improve neuroblast survival and promote neuroblast migration towards the implant. PCL scaffolds were able to support neuroblast infiltration and migration along the implant tract. In the presence of the BDNF-mimetic, neuroblasts were able to migrate towards the implant via the parenchyma, and their persistence within the implants was prolonged. In addition, the BDNF-mimetic improved implant integration and increased local neuronal plasticity by increasing neurite sprouting at the tissue-implant interface. SMI32+ neurites were observed inside scaffolds at 21 days but not 8 days post implantation, indicating that at least some of the infiltrated neuroblasts had differentiated into neurons.nonenoneFon, Deniece; Zhou, Kun; Ercole, Francesca; Fehr, Friederike; Marchesan, Silvia; Minter, Myles R.; Crack, Peter J.; Finkelstein, David I.; Forsythe, John SFon, Deniece; Zhou, Kun; Ercole, Francesca; Fehr, Friederike; Marchesan, Silvia; Minter, Myles R.; Crack, Peter J.; Finkelstein, David I.; Forsythe, John S

Cooperation in viscous populations-Experimental evidence

We experimentally investigate the effect of population viscosity (an increased probability to interact with others of one's type or group) on cooperation in a standard prisoner's dilemma environment. Subjects can repeatedly choose between two groups that differ in the defector gain in the associated prisoner's dilemma. Choosing into the group with the smaller defector-gain can signal one's willingness to cooperate. We find that viscosity produces an endogenous sorting of cooperators and defectors and persistently high rates of cooperation. Higher viscosity leads to a sharp increase in overall cooperation rates and in addition positively affects the subjects' preferences for cooperation. © 2008 Elsevier Inc. All rights reserved

An Evolutionary Analysis of Buyer Insurance and Seller Reputation in Online Markets

Trust, online markets, eBay, reputation mechanism, moral hazard, evolutionary game theory,