Neural correlates of trust

Trust is a critical social process that helps us to cooperate with others and is present to some degree in all human interaction. However, the underlying brain mechanisms of conditional and unconditional trust in social reciprocal exchange are still obscure. Here, we used hyperfunctional magnetic resonance imaging, in which two strangers interacted online with one another in a sequential reciprocal trust game while their brains were simultaneously scanned. By designing a nonanonymous, alternating multiround game, trust became bidirectional, and we were able to quantify partnership building and maintenance. Using within- and between-brain analyses, an examination of functional brain activity supports the hypothesis that the preferential activation of different neuronal systems implements these two trust strategies. We show that the paracingulate cortex is critically involved in building a trust relationship by inferring another person's intentions to predict subsequent behavior. This more recently evolved brain region can be differently engaged to interact with more primitive neural systems in maintaining conditional and unconditional trust in a partnership. Conditional trust selectively activated the ventral tegmental area, a region linked to the evaluation of expected and realized reward, whereas unconditional trust selectively activated the septal area, a region linked to social attachment behavior. The interplay of these neural systems supports reciprocal exchange that operates beyond the immediate spheres of kinship, one of the distinguishing features of the human species.     

Money and trust among strangers

What makes money essential for the functioning of modern society? Through an experiment, we present evidence for the existence of a relevant behavioral dimension in addition to the standard theoretical arguments. Subjects faced repeated opportunities to help an anonymous counterpart who changed over time. Cooperation required trusting that help given to a stranger today would be returned by a stranger in the future. Cooperation levels declined when going from small to large groups of strangers, even if monitoring and payoffs from cooperation were invariant to group size. We then introduced intrinsically worthless tokens. Tokens endogenously became money: subjects took to reward help with a token and to demand a token in exchange for help. Subjects trusted that strangers would return help for a token. Cooperation levels remained stable as the groups grew larger. In all conditions, full cooperation was possible through a social norm of decentralized enforcement, without using tokens. This turned out to be especially demanding in large groups. Lack of trust among strangers thus made money behaviorally essential. To explain these results, we developed an evolutionary model. When behavior in society is heterogeneous, cooperation collapses without tokens. In contrast, the use of tokens makes cooperation evolutionarily stable.     

Power decreases trust in social exchange

How does lacking vs. possessing power in a social exchange affect people’s trust in their exchange partner? An answer to this question has broad implications for a number of exchange settings in which dependence plays an important role. Here, we report on a series of experiments in which we manipulated participants’ power position in terms of structural dependence and observed their trust perceptions and behaviors. Over a variety of different experimental paradigms and measures, we find that more powerful actors place less trust in others than less powerful actors do. Our results contradict predictions by rational actor models, which assume that low-power individuals are able to anticipate that a more powerful exchange partner will place little value on the relationship with them, thus tends to behave opportunistically, and consequently cannot be trusted. Conversely, our results support predictions by motivated cognition theory, which posits that low-power individuals want their exchange partner to be trustworthy and then act according to that desire. Mediation analyses show that, consistent with the motivated cognition account, having low power increases individuals’ hope and, in turn, their perceptions of their exchange partners’ benevolence, which ultimately leads them to trust.Understanding the circumstances under which individuals trust other individuals is of enduring interest to social scientists from different backgrounds (1), including sociologists (2), psychologists (3), political scientists (4), and economists (5). Trust is a critical ingredient in successful social exchange (6), but the threat of misplacing one’s trust and suffering the detrimental consequences of trust breaches causes people to be very careful in deciding to whom to make themselves vulnerable (7–9). Thus, researchers have paid considerable attention to the factors that facilitate or hinder trust in various settings (10–15).However, one potentially important source of variation in trust has received relatively little attention so far—namely, power (16). This omission in the literature is surprising because many—if not most—trust relationships involve nontrivial power inequalities between exchange partners. Examples include relationships between patients and doctors, students and professors, employees and supervisors, and small and large firms. Power-dependence theory (17–19) emphasizes that behavior in social exchange relationships is significantly affected by power inequalities that involve one actor depending on the other, with dependence being a positive function of the relative value of the exchange resource and a negative function of the availability of the exchange resource from alternatives. This conceptualization of power in terms of structural dependence has become the dominant approach in both sociological and psychological inquiry (20, 21). The prevalence of power inequalities in relationships in which trust is critical leads us to ask: Does having power or lacking power increase or decrease an actor’s tendency to place trust in others?In response to this question, we can derive two directly opposing predictions from distinct theoretical accounts. First, the encapsulated interest account (22–25) assumes that people engage in rational calculations about whether it will pay off to encapsulate the interests of their exchange partners and to behave in a trustworthy fashion. One key reason for trustees to be trustworthy is their motivation to maintain the relationship (22, 26). The encapsulated interest account further assumes that trustors put themselves in the position of the trustee to predict how the trustee will behave. Therefore, when considering whether or not to trust someone, an individual assesses how valuable the relationship is to the other person. Applying this line of thinking to a relationship involving a power inequality, the power-advantaged party should have reason to believe that the power-disadvantaged party places high value on the relationship. This belief is based on the notion that people low in power view the exchange resource as valuable, possess few alternatives to access this resource, and therefore are highly dependent on the exchange partners they do have (17, 27). Given this dependence, low-power individuals should place high value on their existing relationships, strive to maintain them, and thus behave cooperatively. In anticipation of this reasoning, the more powerful party should perceive their less powerful exchange partner as trustworthy and in turn be willing to trust that partner. Conversely, the less powerful party should be aware of the fact that their more powerful partner has several other valuable exchange opportunities, is less dependent on any particular relationship, and thus has greater freedom to act opportunistically when doing so would result in higher immediate returns (also see SI Formal Analysis of Incentive Structures). In sum, according to the encapsulated interest account, more powerful actors should place greater trust in others than less powerful actors.Second, the motivated cognition account (28–32) starts with the assumption that people strive to arrive at conclusions they want to arrive at in an effort to mitigate cognitive dissonance. Accordingly, the decision to place trust may be based more on one’s motivation to protect oneself from unwanted realities than on relatively rational calculations of the other party’s deliberations. In particular, with increasing dependence, people will be motivated to see their partner as more trustworthy to avoid the anxiety inherently attached to their feelings of dependence. Power-disadvantaged actors thus effectively protect themselves by perceiving power holders in a positive light, even if little or no relevant information would support such perceptions. Their hope that their powerful partner will be trustworthy thus dominates their cognition and decision making. The powerful partner, conversely, has no reason to engage in significant motivated cognition (33). Having multiple valuable exchange alternatives available, the power-advantaged party has little incentive to view his/her partner in a better light than the objective information would justify. In sum, according to the motivated cognition account, more powerful actors should place less trust in others compared to less powerful actors.We report four studies that investigated these opposing predictions (details are in SI Materials and Methods). Throughout this research, we sought to generalize our results across different experimental tasks using various operationalizations of power and both perceptual and behavioral measures of trust. In studies 1–4, we tested whether being in a weaker or stronger power position is linked to differences in perceptual trust (study 1) and behavioral trust (studies 2–4). Additionally, in study 4, we extended our research by starting to examine which mechanisms help explain why power is associated with trust.     

The effect of trust and change in trust on self-rated health: A longitudinal study among aging people

This study examined whether trust predicted subsequent self-rated health over time at 3 years follow-up among aging people, and whether changes in trust were associated with self-rated health. Longitudinal, questionnaire-based data were collected from three age cohorts (born in 1926–1930, 1936–1940, and 1946–1950) living in the Province of Päijät-Häme, southern Finland. The response rate at the baseline in 2002 was 66% (n = 2815). The follow-up was carried out in 2005, with 79% of eligible individuals participating (n = 2216). Logistic regression analyses were used to derive the results. High trust was a strong predictor for good self-rated health at the follow-up. Adjusting for background variables, however, attenuated the association. In addition, good self-rated health was most common among men with sustained high trust, among women the association was somewhat weaker. Among men improvement in trust was associated with good self-rated health, but this correlation weakened after multiple adjustments. Thus, longitudinally trust is an important contributor to self-rated health among aging people. Moreover, improvement of trust but also the stability of high trust especially among men indicate better self-rated health. Trust has a positive effect on health and should therefore be seen as a significant element in health promotion.     

Rebuilding trust in proton pump inhibitor therapy

Introduction of proton pump inhibitor (PPI) therapy into clinical practice has revolutionized treatment approach to acid-related diseases. With its clinical success came a widespread use of PPI therapy. Subsequently, several studies found that PPIs were oftentimes overprescribed in primary care and emergency setting, likely attributed to seemingly low side-effect profile and physicians having low threshold to initiate therapy. However, now there is a growing concern over PPI side-effect profile among both patients and providers. We would like to bring more awareness to the currently available guidelines on PPI use, discuss clinical indications for PPIs and the evidence behind the reported side-effects. We hope that increased awareness of proper PPI use will make the initiation or continuation of therapy a well informed and an evidence-based decision between patient and physician. We also hope that discussing evidence behind the reported side-effect profile will help clarify the growing concerns over PPI therapy.