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We propose a model of cumulative advantage (CA) as an unintended consequence of the choices of a population of individuals. Each individual searches for a high quality object from a set comprising high and low quality objects. Individuals rationally learn from their own experience with objects (reinforcement learning) and from the observation of others' choices (social learning). We show that CA emerges inexorably as individuals rely more on social learning and as they learn from more rather than fewer others. Our theory argues that CA has social dilemma features: the benefits of CA could be enjoyed with modest drawbacks provided individuals would practice restraint in their social learning. However, when practiced by everyone such restraint goes against the individual's self-interest. [ABSTRACT FROM AUTHOR]

Bacteria produce a structural layer of peptidoglycan (PG) that enforces cell shape, resists turgor pressure, and protects the cell. As bacteria grow and divide, the existing layer of PG is remodeled and PG fragments are released. Enterics such as Escherichia coli go to great lengths to internalize and reutilize PG fragments. E. coli is estimated to break down one-third of its cell wall, yet only loses ~0 to 5% of meso-diaminopimelic acid, a PG-specific amino acid, per generation. Two transporters were identified early on to possibly be the primary permease that facilitates PG fragment recycling, i) AmpG and ii) the Opp ATP binding cassette transporter in conjunction with a PG-specific periplasmic binding protein, MppA. The contribution of each transporter to PG recycling has been debated. Here, we have found that AmpG and MppA/Opp are differentially regulated by carbon source and growth phase. In addition, MppA/Opp is uniquely capable of high-affinity scavenging of muropeptides from growth media, demonstrating that AmpG and MppA/Opp allow for different strategies of recycling PG fragments. Altogether, this work clarifies environmental contexts under which E. coli utilizes distinct permeases for PG recycling and explores how scavenging by MppA/Opp could be beneficial in mixed communities. [ABSTRACT FROM AUTHOR]

Social networks are fundamental to the broad scale cooperation observed in human populations. But by structuring the flow of benefits from cooperation, networks also create and sustain macro-level inequalities. Here we ask how two aspects of inequality shape the evolution of cooperation in dynamic social networks. Results from a crowdsourced experiment (N = 1080) show that inequality alters the distribution of cooperation within networks such that participants engage in more costly cooperation with their wealthier partners in order to maintain more valuable connections to them. Inequality also influences network dynamics, increasing the tendency for participants to seek wealthier partners, resulting in structural network change. These processes aggregate to alter network structures and produce greater system-level inequality. The findings thus shed critical light on how networks serve as both boon and barrier to macro-level human flourishing. [ABSTRACT FROM AUTHOR]

How should we measure people's perceptions of—and attitudes about—economic inequality? A recent literature seeks to quantify the level of inequality that people, especially Americans, perceive and prefer in society. These findings have garnered much attention from both social scientists and the public. But many of the methods used in this literature are either known to have methodological issues or have not been thoroughly compared against other methods. Thus it is not clear which, if any, are valid and reliable measures of perceived, or preferred, inequality. To assess these measures, we conducted a large web-based study (N = 831) to compare key methods for measuring perceived inequality and their related justice attitudes. In addition to comparing the resultant summary statistics, we assess how well the different measures correlate with each other and with Likert scale measures of perceived inequality. Our analysis reveals a range of issues with these measures, including failure to provide logical responses, large method effects on point estimates of inequality, and low correlations between methods and with criteria measures. We conclude our analysis with three recommendations for researchers aiming to measure inequality perceptions and preferences. [ABSTRACT FROM AUTHOR]

The bacterial peptidoglycan (PG) cell wall is remodeled during growth and division, releasing fragments called muropeptides. Muropeptides can be internalized and reused in a process called PG recycling. Escherichia coli is highly devoted to recycling muropeptides and is known to have at least two transporters, AmpG and OppBCDF, that import them into the cytoplasm. While studying mutants lacking AmpG, we unintentionally isolated mutations that led to the altered expression of a third transporter, CadB. CadB is normally upregulated under acidic pH conditions and is an antiporter for lysine and cadaverine. Here, we explored if CadB was altering PG recycling to assist in the absence of AmpG. Surprisingly, CadB overexpression was able to restore PG recycling when both AmpG and OppBCDF were absent. CadB was found to import freed PG peptides, a subpopulation of muropeptides, through a promiscuous activity. Altogether, our data support that CadB is a third transporter capable of contributing to PG recycling. [ABSTRACT FROM AUTHOR]

The asymmetric outer membrane (OM) of Gram-negative bacteria functions as a selective permeability barrier to the environment. Perturbations to OM lipid asymmetry sensitize the cell to antibiotics. As such, mechanisms involved in lipid asymmetry are fundamental to our understanding of OM lipid homeostasis. One such mechanism, the Maintenance of lipid asymmetry (Mla) pathway has been proposed to extract mislocalized glycerophospholipids from the outer leaflet of the OM and return them to the inner membrane (IM). Work on this pathway in Acinetobacter baumannii support conflicting models for the directionality of the Mla system being retrograde (OM to IM) or anterograde (IM to OM). Here, we show conclusively that A. baumannii mla mutants exhibit no defects in anterograde transport. Furthermore, we identify an allele of the GTPase obgE that is synthetically sick in the absence of Mla; providing another link between cell envelope homeostasis and stringent response. [ABSTRACT FROM AUTHOR]

Lipopolysaccharides (LPS) are essential envelope components in many Gram‐negative bacteria and provide intrinsic resistance to antibiotics. LPS molecules are synthesized in the inner membrane and then transported to the cell surface by the LPS transport (Lpt) machinery. In this system, the ATP‐binding cassette (ABC) transporter LptB2FGC extracts LPS from the inner membrane and places it onto a periplasmic protein bridge through a poorly understood mechanism. Here, we show that residue E86 of LptB is essential for coupling the function of this ATPase to that of its partners LptFG, specifically at the step where ATP binding drives the closure of the LptB dimer and the collapse of the LPS‐binding cavity in LptFG that moves LPS to the Lpt periplasmic bridge. We also show that defects caused by changing residue E86 are suppressed by mutations altering either LPS structure or transmembrane helices in LptG. Furthermore, these suppressors also fix defects in the coupling helix of LptF, but not of LptG. Together, these results support a transport mechanism in which the ATP‐driven movements of LptB and those of the substrate‐binding cavity in LptFG are bi‐directionally coordinated through the rigid‐body coupling, with LptF's coupling helix being important in coordinating cavity collapse with LptB dimerization. [ABSTRACT FROM AUTHOR]

The article discusses on experimental evidence that each form of reciprocity is robust to the presence of other forms of reciprocity. Topics discussed include information on topological features of human social networks with multiple types of reciprocity; understanding of human prosociality in account for the fact that the various forms of reciprocity tend to co-occur in nature; and information on high levels of prosociality observed in human social networks.

Prior research using the Moral Foundations Questionnaire (MFQ) has established that political ideology is associated with self-reported reliance on specific moral foundations in moral judgments of acts. MFQ items do not specify the agents involved in the acts, however. By specifying agents in MFQ items we revealed blatant political double standards. Conservatives thought that the same moral foundation was more relevant if victims were agents that they like (i.e., corporations and other conservatives) but less relevant when the same agents were perpetrators. Liberals showed the same pattern for agents that they like (i.e., news media and other liberals). A UK sample showed much weaker political double standards with respect to corporations and news media, consistent with feelings about corporations and news media being much less politicized in the UK than in the US. We discuss the implications for moral foundations theory. [ABSTRACT FROM AUTHOR]

Gram-negative bacteria have a unique cell surface that can be modified to maintain bacterial fitness in diverse environments. A well-defined example is the modification of the lipid A component of lipopolysaccharide (LPS), which promotes resistance to polymyxin antibiotics and antimicrobial peptides. In many organisms, such modifications include the addition of the amine-containing constituents 4-amino-4-deoxy-l-arabinose (l-Ara4N) and phosphoethanolamine (pEtN). Addition of pEtN is catalyzed by EptA, which uses phosphatidylethanolamine (PE) as its substrate donor, resulting in production of diacylglycerol (DAG). DAG is then quickly recycled into glycerophospholipid (GPL) synthesis by the DAG kinase A (DgkA) to produce phosphatidic acid, the major GPL precursor. Previously, we hypothesized that loss of DgkA recycling would be detrimental to the cell when LPS is heavily modified. Instead, we found that DAG accumulation inhibits EptA activity, preventing further degradation of PE, the predominant GPL of the cell. However, DAG inhibition of pEtN addition results in complete loss of polymyxin resistance. Here, we selected for suppressors to find a mechanism of resistance independent of DAG recycling or pEtN modification. Disrupting the gene encoding the adenylate cyclase, cyaA, fully restored antibiotic resistance without restoring DAG recycling or pEtN modification. Supporting this, disruptions of genes that reduce CyaA-derived cAMP formation (e.g., ptsI) or disruption of the cAMP receptor protein, Crp, also restored resistance. We found that loss of the cAMP-CRP regulatory complex was necessary for suppression and that resistance arises from a substantial increase in l-Ara4N-modified LPS, bypassing the need for pEtN modification. [ABSTRACT FROM AUTHOR]

Social scientists often study the flow of material and social support as generalized exchange systems. These systems are associated with an array of benefits to groups and communities, but their existence is problematic, because individuals may be motivated to take from the system without giving back to it. Researchers have identified two broad processes governing prosociality in generalized exchange systems: generalized reciprocity (a person who receives help from someone pays it forward by helping a third person) and indirect reciprocity (a person who helps another establishes a prosocial reputation and, as a consequence, later receives help from a third person). Although generalized exchange systems can be based on either process, generalized and indirect reciprocity are based on different mechanisms and, with few exceptions, have been investigated independently. Here we present an integrated approach to generalized exchange that (1) specifies when each process is most likely to promote prosocial behavior, (2) details the implications for resource inequalities in generalized exchange systems, and (3) describes how generalized and indirect reciprocity jointly influence prosocial behavior. Results from four new experiments strongly support the theoretical arguments. [ABSTRACT FROM AUTHOR]

The rewards people receive are often taken as indirect evidence of their merit. We outline an argument that addresses how the magnitude of macrolevel income inequalities affects perceptions of the distribution of merit in a society. We propose that higher levels of economic inequality will lead to perceptions of greater differences in merit such that societies with higher inequality will be characterized by a larger “merit gap,” namely, larger differences in the perceived merit of the rich and poor. We test these arguments using an online experiment that manipulated the level of inequality (high vs. low) in an anonymized society. Participants perceived a larger merit gap in high versus low inequality societies. Our arguments and findings have implications for attitudes about inequality and redistributive policies. [ABSTRACT FROM AUTHOR]

Research on collective action problems and the provision of public goods has yielded an array of important insights into why people sacrifice for their groups, but ignores the processes that bring people into those groups in the first place. The literature is also silent on the fact that groups providing similar public goods often compete with one another to attract new members. We extend the reach of theories of collective action problems to bring them to bear on these interrelated issues. Results from four experiments support our predictions about when group members compete to attract new adherents by sacrificing more for group goals. Further, we find that prospective members join more productive groups at much higher rates and then contribute to them at high levels. These processes give way to cumulative advantage, whereby initially productive groups continually attract new members. Thus competition for members can yield large inequalities in the size and success of collective action groups. [ABSTRACT FROM AUTHOR]

This paper bridges insights from theories of collective action, power, and influence to address the conditions under which group leaders solve collective action problems. We show how leaders' behaviors impact the success of collective action groups as a whole via both power and influence processes. In a laboratory experiment, groups first completed a baseline measure of cooperation in a public good dilemma without punishment. In a second phase, the capacity to punish was introduced. One condition, the "peer-sanctioning condition," was equivalent to the prevailing solution in the experimental literature on collective action, where the ability to punish others is distributed equally among all group members. In the other two conditions, only a single group "leader" could punish; we varied whether the person assigned to lead was otherregarding (prosocial) or self-regarding (proself). The results support our prediction that prosocial leaders increase their contributions to the group after ascending to leadership, while proself leaders reduce their contributions. Further, as expected, rank-andfile group members are influenced by leaders' contribution behaviors; as a result, prosocial-led groups as a whole were substantially more productive than proself-led groups. Indeed, as predicted, prosocial leaders were even more effective in maintaining large group contributions than the standard peer-sanctioning system. These findings suggest that putting power and influence in the right hands solves collective action problems and promotes collective welfare. [ABSTRACT FROM AUTHOR]

The cell surface of most Gram-negative bacteria is covered with lipopolysaccharide (LPS). The network of charges and sugars provided by the dense packing of LPS molecules in the outer leaflet of the outer membrane interferes with the entry of hydrophobic compounds into the cell, including many antibiotics. In addition, LPS can be recognized by the immune system and plays a crucial role in many interactions between bacteria and their animal hosts. LPS is synthesized in the inner membrane of Gram-negative bacteria, so it must be transported across their cell envelope to assemble at the cell surface. Over the past two decades, much of the research on LPS biogenesis has focused on the discovery and understanding of Lpt, a multi-protein complex that spans the cell envelope and functions to transport LPS from the inner membrane to the outer membrane. This paper focuses on the early steps of the transport of LPS by the Lpt machinery: the extraction of LPS from the inner membrane. The accompanying paper (May JM, Sherman DJ, Simpson BW, Ruiz N, Kahne D. 2015 Phil. Trans. R. Soc. B 370, 20150027. (doi:10.1098/rstb.2015.0027)) describes the subsequent steps as LPS travels through the periplasm and the outer membrane to its final destination at the cell surface. [ABSTRACT FROM AUTHOR]

In explaining the sources of cooperation and prosocial behavior, psychologists, behavioral economists, and biologists often focus on factors internal to the individual, such as altruistic motivations, other-regarding preferences, and prosocial emotions. By contrast, sociologists typically emphasize social forces external to the individual, including norms, reputation systems, and social networks. Here we review evidence for these rules, reputations, and relations, showing that they have powerful and pervasive effects on cooperation and prosocial behavior. Our discussion highlights two emergent themes of the reviewed literature. First, although these classes of sociological mechanisms typically promote cooperation, their presence can also create ambiguity for individuals regarding the reasons for their own and others' prosocial acts, and that ambiguity can undermine future prosociality in subsequent settings where the mechanisms are absent. Second, altruistic preferences and social mechanisms often interact, such that the causal significance of altruism is attenuated where these mechanisms are present. [ABSTRACT FROM AUTHOR]

In this article, the editor talks about the publications of the perodical on social psychology.

Jatropha curcasis a well-known source of non-edible vegetable oil that is being promoted as an energy source and high quality feedstock in biodiesel production, especially in developing countries. The potential that the resulting seedcake by-product from jatropha oil extraction (˜70% by volume) could also be used as a component in animal feed raises the prospect that a commercially viable jatropha-based industry could be developed. To date, however, the use of jatropha seedcake in livestock feed formulation has been constrained by the presence of phorbol esters (PE), which are known promutagenic and toxic compounds, and by the inability to eliminate PE by cost-effective means. Using seedcake by-product collected from a commercial facility in West Africa that processes jatropha biodiesel, this study demonstrates cost-effective measures of eliminating PE from jatropha seedcake using a combination of solar irradiation and ozonation. [ABSTRACT FROM AUTHOR]

Employers use ideologically-tinged rhetoric to justify workplace discrimination. We argue that workers will be less likely to label biased treatment against them as discriminatory when they subscribe to those ideologies as well. We tested this prediction and the consequences of labeling for work attitudes and performance using an experiment that assigned parents to a low-status position in a work group, varying whether the decision invoked biased, ideological assumptions about parenthood. As expected, ideology drove mothers' (but not fathers') labeling. Mothers were less likely to label biased treatment against them as discriminatory when they were conservative and when they subscribed to separate spheres and ideal worker ideologies. Mothers who labeled their treatment as discriminatory had more negative work attitudes than those who did not, but also tended to appeal the decision. Ideology thus shapes whether people label discrimination when it occurs as well as their subsequent work attitudes and justice-seeking behaviors. [ABSTRACT FROM AUTHOR]

Social psychology and related disciplines are seeing a resurgence of interest in replication, as well as actual replication efforts. But prior work suggests that even a clear demonstration that a finding is invalid often fails to shake acceptance of the finding. This threatens the full impact of these replication efforts. Here we show that the actions of two key players – journal editors and the authors of original (invalidated) research findings – are critical to the broader public’s continued belief in an invalidated research conclusion. Across three experiments, we show that belief in an invalidated finding falls sharply when a critical failed replication is published in the same – versus different – journal as the original finding, and when the authors of the original finding acknowledge that the new findings invalidate their conclusions. We conclude by discussing policy implications of our key findings. [ABSTRACT FROM AUTHOR]

Classic sociological solutions to cooperation problems were rooted in the moral judgments group members make about one another's behaviors, but more recent research on prosocial behaviors has largely ignored this foundational work. Here, we extend theoretical accounts of the social effect of moral judgments. Where scholars have emphasized the roles of moral judgments in clarifying moral boundaries and punishing deviants, we present two less intuitive paths from moral judgments to social behavior. We argue that those who engage in moral judgments subsequently act more morally. Further, we argue that group members anticipate the more moral behavior of judges, trusting them more under situations of risk and uncertainty. We thus establish paths from moral judgments to the primary foundations of voluntary cooperation: trust and trustworthiness. The results of three experiments support the predicted effects: Participants randomly assigned to make moral judgments were more trustworthy in subsequent interactions (Study 1). A follow-up experiment sought to clarify the underlying mechanism, showing that making moral judgments led individuals to view themselves as more moral (Study 2). Finally, audience members anticipated the greater trustworthiness of moral judges (Study 3). [ABSTRACT FROM PUBLISHER]

Collective action researchers have focused on injunctive norms that specify approved behavior as a panacea for collective action problems. We investigate whether descriptive norms (similar behavior) can also solve these problems. We argue that descriptive norms generate social identification, which then sustains conformity to expectations. Consequently, descriptive norms can characterize both cooperation and noncooperation, such that cooperative norms sustain successful collective action while noncooperative norms result in collective action failure. Results from two laboratory experiments supported the hypothesis that descriptive norms can sustain collective action success and failure. Further, while normative non-­cooperation eroded cooperation for high contributors, normative cooperation had little affect on low contributors. This asymmetry points to a paradox: because they promote group identification, noncooperative descriptive norms can be self-sustaining, with deleterious outcomes. [ABSTRACT FROM PUBLISHER]

A recent survey of inequality (Norton and Ariely, Perspectives on Psychological Science, 6, 9-12) asked respondents to indicate what percent of the nation's total wealth is--and should be--controlled by richer and poorer quintiles of the U.S. population. We show that such measures lead to powerful anchoring effects that account for the otherwise remarkable findings that respondents reported perceiving, and desiring, extremely low inequality in wealth. We show that the same anchoring effects occur in other domains, namely web page popularity and school teacher salaries. We introduce logically equivalent questions about average levels of inequality that lead to more accurate responses. Finally, when we made respondents aware of the logical connection between the two measures, the majority said that typical responses to the average measures, indicating higher levels of inequality, better reflected their actual perceptions and preferences than did typical responses to percent measures. [ABSTRACT FROM AUTHOR]

Most work on collective action assumes that group members are undifferentiated by status, or standing, in the group. Yet such undifferentiated groups are rare, if they exist at all. Here we extend an existing sociological research program to address how extant status hierarchies help organize collective actions by coordinating how much and when group members should contribute to group efforts. We outline three theoretically derived predictions of how status hierarchies organize patterns of behavior to produce larger public goods. We review existing evidence relevant to two of the three hypotheses and present results from a preliminary experimental test of the third. Findings are consistent with the model. The tendency of these dynamics to lead status-differentiated groups to produce larger public goods may help explain the ubiquity of hierarchy in groups, despite the often negative effects of status inequalities for many group members. [ABSTRACT FROM AUTHOR]

Social scientists have intensely debated the use of deception in experimental research, and conflicting norms governing the use of deception are now firmly entrenched along disciplinary lines. Deception is typically allowed in sociology and social psychology but proscribed in economics. Notably, disagreements about the use of deception are generally not based on ethical considerations but on pragmatic grounds: the anti-deception camp argues that deceiving participants leads to invalid results, while the other side argues that deception has little negative impact and, under certain conditions, can even enhance validity. These divergent norms governing the use of deception are important because they stifle interdisciplinary research and discovery, create hostilities between disciplines and researchers, and can negatively impact the careers of scientists who may be sanctioned for following the norms of their home discipline. We present two experimental studies aimed at addressing the issue empirically. Study 1 addresses the effects of direct exposure to deception, while Study 2 addresses the effects of indirect exposure to deception. Results from both studies suggest that deception does not significantly affect the validity of experimental results. [ABSTRACT FROM PUBLISHER]

Abstract: We outline a new explanation of discrimination against numerical minorities. In contrast to prior work that focuses on how the content of categories affects discrimination, our argument describes how the size of categories leads to discrimination. Specifically, we argue that, when comparing multiple categories, actors tend to view larger categories as more closely approximating an underlying population than smaller ones. As a result, a decision maker will tend to expect that members of a numerical majority are more likely to be what he/she is searching for, whether it is the best or worst candidate. We report the results of two studies designed to test these arguments. To demonstrate the generality of the proposed mechanism, Study 1 tested the argument in a non-social domain. Participants disproportionately favored the majority (vs. minority) category when searching for a single winning lottery ticket, and favored the minority category when the goal was to avoid a single losing ticket. Our second study supported an additional implication of the argument in a social domain: decision makers tended to rank highly qualified majority job candidates as better than equally qualified minority candidates, and relatively unqualified majority candidates as worse than equally unqualified minority candidates. [Copyright &y& Elsevier]

Abstract: This paper introduces a new model to explain perceptions of unfairness in resource allocations between multiple recipients. The model yields several novel predictions, all confirmed in a series of new empirical tests. For instance, while much prior research focuses on the differences between the judge’s share and others’ shares, we argue that people also care about differences between others’ shares. In particular, the presence of a single loser increases perceptions of unfairness. We also study individual variation in sensitivity to the single-loser dimension. Most centrally, we offer empirical support for the existence – indeed the prevalence – of ostraphobics, individuals with an acute sensitivity to being “ostracized” as a sole loser. We show that ostraphobics perceive unfairness more strongly than other types, are higher in need to belong and fear of negative evaluation, and are more prone to a heretofore unrecognized type of preference reversal with respect to fairness. [Copyright &y& Elsevier]

This research addresses a long standing puzzle in the social sciences: why are stratified social systems accepted as legitimate (the way things “ought” to be) by those who are advantaged and those who are disadvantaged by them? We build on previous studies of self-evaluations to explain the legitimation of inequality. The research consists of two experiments designed to test the self-evaluation theory of legitimacy. The theory proposes that structural inequality becomes legitimated when individuals’ self-evaluations and the level of resources they receive are congruent. Study 1 examines the impact of structural power on self-evaluations. Results show that participants randomly assigned to advantaged positions in power structures earn more rewards and, as a result, develop higher self-evaluations than those randomly assigned to disadvantaged positions. Study 2 addresses the relationship between self-evaluations and legitimated structural inequality by testing competing hypotheses of legitimacy. The results partially support the self-evaluation theory and partially support competing arguments about legitimacy. We conclude with a discussion of the implications of our work and suggestions for future research. [Copyright &y& Elsevier]

Generalized trust, or trust in strangers, has been traced to a wide range of societal benefits. But generalized trust is not sustainable in the absence of widespread generalized trustworthiness, that is, the tendency for strangers to honor trust extended to them. While there has been much work on the origins and consequences of generalized trust, surprisingly little research has addressed the antecedents of generalized trustworthiness. We argue that generalized trustworthiness is negatively affected by prior exposure to a ubiquitous extrinsic motivator of trustworthy behavior, contracts. Specifically, drawing on classic social psychological research on the overjustification effect, we argue that actors previously constrained by contracts will attribute their own 'trustworthy' behavior in those interactions to the contract itself. According to overjustification arguments, this misattribution should lead to a decrease in intrinsic motivations to act trustworthily in interactions where the actor is not constrained by the contract. Results of a new experiment support this argument. [ABSTRACT FROM AUTHOR]

A persistent puzzle in the social and biological sciences is the existence of prosocial behavior, actions that benefit others, often at a cost to oneself. Recent theoretical models and empirical studies of indirect reciprocity show that actors behave prosocially in order to develop an altruistic reputation and receive future benefits from third parties. Accordingly, individuals should stop investing in reputations via prosocial behavior when a future benefit (via indirect reciprocity) is unlikely. The conclusion that the absence of reputational incentives necessarily leads to egoistic behavior contrasts sharply with models of heterogeneous social preferences. Such models demonstrate the theoretical plausibility of populations composed of egoists and altruists. Results of Study One show that actors classified a priori as egoists respond strategically to reputational incentives, whereas those classified a priori as altruists are less affected by these incentives. Egoists act prosocially when reputational incentives are at stake but not when opportunities for indirect reciprocity are absent, while altruists tend to act prosocially regardless of whether reputational incentives are present. These results suggest that altruistic behavior can result from non-strategic altruism or reputation-building egoism. Study Two replicates these results and explores indirect reciprocation of others' prosocial acts. We found that altruists indirectly reciprocate at higher levels than egoists, and individuals tend to discount others' prosocial behaviors when they occur in the presence of reputational incentives. As a result, public prosocial behaviors are indirectly reciprocated less than private prosocial behaviors. In line with our argument that altruists pay less attention to reputational incentives, egoists showed a greater tendency than altruists to discount others' public prosocial behaviors. The results support the growing focus on heterogeneity of individuals' social preferences in models of altruism and indirect reciprocity. [ABSTRACT FROM AUTHOR]

Many scholars have concluded that blacks are less trusting than whites. The research presented here calls that conclusion into question. Previous research has been based on the standard trust measure, which may not be well suited to understanding how trust varies with social categories such as race. Building on theories of self-categorization and social identity, we argue that blacks are not less trusting than whites as suggested in previous work. Instead trust is expected to be greater within race-category boundaries than across race-category boundaries. A new experiment designed to test this argument is employed. The results strongly support our predictions. This research also addresses how trustworthiness varies with race-category. Results for trustworthiness do not map on to those for trust. Instead, blacks in this research show a higher level of trustworthiness than whites, regardless of other's race-category. [ABSTRACT FROM AUTHOR]

This article presents a refined explanation of why minimal group identities affect cooperation in social dilemmas. The refined approach builds on key tenets of social identity theory to argue that identity affects cooperation by leadings actors to maximize ingroup outcomes and minimize ingroup inequalities. A key implication of the argument is that social identity is predicted to reduce actors' responses to the ‘greed component’ in social dilemmas (the incentive to ‘free-ride’ on others' cooperation), but that it will not affect actors' responses to the ‘fear component’ (the motivation to avoid being ‘suckered’). These predictions stand in contrast to those of two existing explanations of social identity and cooperation. The three arguments are tested against the results of two new experiments. Overall, the results support the refined approach. [ABSTRACT FROM AUTHOR]

Previous studies by Holmes, Miller, and Lerner (2002) support the norm of self-interest and exchange fiction hypotheses. Together these arguments state that people want to act on compassionate feelings (e.g., by donating to charities) but are reluctant to do so if they cannot justify their behavior as being in line with their own self-interest. Thus a person will be more likely to contribute to a charity when he or she receives a product in exchange for the contribution. This exchange fiction gives the person egoistic cover for the compassionate act. In this paper we critically evaluate the evidence for this line of reasoning and offer an alternative explanation for that evidence based on cognitive dissonance theory. We report the results of a new field experiment designed to tease apart the exchange fiction argument and the alternative approach. Results of the study support our application of dissonance theory over the exchange fiction account. [ABSTRACT FROM AUTHOR]

This paper bridges two lines of research. One line shows that social relations in the southern United States are more "collectivist" than social relations in non-southern regions. The second line of work argues that collectivist social relations generate lower levels of general trust than individualist social relations. At the intersection of these two arguments is the prediction that Southerners are, on average, less trusting than non-Southerners. I test this prediction using trust measures taken from the General Social Survey. As expected, results from whites, but not blacks, show the predicted regional differences. Importantly, regional differences in trust occur after controlling for regional variation in other factors related to trust. I conclude by outlining various implications of the findings and questions for future research. [ABSTRACT FROM AUTHOR]

The growing body of literature on coalitions in exchange networks has addressed issues such as the kind of social dilemmas posed and how structurally disadvantaged actors overcome free-rider problems. We add to this stream of research by focusing explicitly on what low-power actors can gain from collective action. We offer theory that predicts whether actors can gain a collective good by forming coalitions and, if so, the size of that good, for all types of network connection. The results from new experiments yield strong support for the predictions. Results show that (1) collective goods are latent in some, but not all, types of exchange structures; (2) when present, collective good size is determined by connection type; and (3) these goods are made manifest through collective action. Among other phenomena, the theory explains why networks that generate identical exchange ratios when participants act independently can produce different size collective goods when they act collectively. This article concludes with a discussion of implications, limitations, and directions for future research. [ABSTRACT FROM AUTHOR]

This research investigates competing arguments about the relationship between power and perception in social networks. One line of research predicts that occupants of structurally advantaged positions have more accurate perceptions of ties in their networks (i.e., who is tied to whom); another line asserts that lower-power actors have more accurate perceptions. On the basis of previous work, we suggest that any relationship between power and perception (whether positive or negative) will be mediated by the distance between the perceiver and relevant ties. We explicate these arguments and test them experimentally. The results suggest that as distance between the perceiver and the tie increases, low-power actors have more accurate perceptions of the network than high-power actors. [ABSTRACT FROM AUTHOR]

A persistent anomaly in the social dilemmas literature is the surprisingly high level of cooperation observed in experimental investigations of the one-shot Prisoners' Dilemma (PD). The exchange heuristic hypothesis and related approaches explain this finding by arguing that actors subjectively transform PD into the Assurance Dilemma. A tendency to transform PD into Assurance is expected to increase cooperation because defection is the dominant strategy in PD, but not in Assurance. Although existing arguments explain the processes through which these subjective transformations occur, they do not predict who actually makes the transformations. This study incorporates arguments from the social values literature and proposes four hypotheses about who transforms PD and how this affects cooperation. The hypotheses are tested against the results of a new experiment. The results strongly support the hypotheses and the overarching argument that "prosocials" transform PD into Assurance, while "individualists" play PD "as is." [ABSTRACT FROM AUTHOR]

Our research aims to bring collective action back into the study of structural determinants of power in social exchange. Previous research has focused primarily on the bargaining power of actors whose locations in exchange networks confer different risks of exclusion. We argue that structural position affects not only bargaining power but also the ability of low-power actors to organize against unequal bargaining power. We hypothesize that collective action among low-power actors is facilitated by identification with others who are structurally disadvantaged. We test two identity-theoretic expected utility models that specify how actors in a mixed-motive coalition game might take into account the payoffs to others in structurally equivalent positions. In the utilitarian model, actors maximize the greatest good to the greatest number. In the collectivist model, actors also seek to minimize in-group inequality. Results show some support for the utilitarian model among female participants and strong support for the collectivist model among both males and females. We speculate about causes of gender differences and identify directions for future exchange-theoretic research on social identity and socially embedded collective action. [ABSTRACT FROM AUTHOR]

Status characteristics theory predicts the emergence and structure of power and prestige orders in task groups from members’ status attributes. This paper argues that application of the burden of proof assumption, central to the theory, is inconsistent with a key concept, generalized expectation state. A reformulation is proposed that eliminates the inconsistency and gives competing predictions for a wide range of situations. The reformulation predicts that, when not directly relevant to task performance, specific characteristics (e.g., athletic or analytical ability) have less impact than diffuse characteristics (race, gender, or education) on performance expectations. The original formulation predicts equal effects. Critical tests are proposed and the paper concludes with additional comparisons of the two formulations on the grounds of parsimony and implications for intervention in settings characterized by status-based inequalities. [ABSTRACT FROM AUTHOR]

This paper integrates research in network exchange and collective action. Network exchange research typically assumes that structurally disadvantaged actors cannot collude. Meanwhile, collective action research shows that cooperation can be undermined by the temptation to "free-ride" on others' efforts. In this paper we extend the scope of network exchange theory by allowing low-power actors to form coalitions. We also extend game-theoretic research by embedding collective action in a network of social relations and power processes. A theory of coalitions in exchange networks is presented, which predicts the critical mass below which coalitions fail to affect power inequality and above which coalitions become unstable. We present the results of a preliminary experimental test of the theory. The results demonstrate not only that coalitions form but even that they can reverse power inequality. However, larger coalitions were more stable than predicted. [ABSTRACT FROM AUTHOR]

The cell surface of the Gram-negative cell envelope contains lipopolysaccharide (LPS) molecules, which form a permeability barrier against hydrophobic antibiotics. The LPS transport (Lpt) machine composed of LptB2FGCADE forms a proteinaceous transenvelope bridge that allows for the rapid and specific transport of newly synthesized LPS from the inner membrane (IM) to the outer membrane (OM). This transport is powered from the IM by the ATP-binding cassette transporter LptB2FGC. The ATP-driven cycling between closed- and open-dimer states of the ATPase LptB2 is coupled to the extraction of LPS by the transmembrane domains LptFG. However, the mechanism by which LPS moves from a substrate-binding cavity formed by LptFG at the IM to the first component of the periplasmic bridge, the periplasmic β-jellyroll domain of LptF, is poorly understood. To better understand how LptB2FGC functions in Escherichia coli, we searched for suppressors of a defective LptB variant. We found that defects in LptB2 can be suppressed by both structural modifications to the core oligosaccharide of LPS and changes in various regions of LptFG, including a periplasmic loop in LptF that connects the substrate-binding cavity in LptFG to the periplasmic β-jellyroll domain of LptF. These novel suppressors suggest that interactions between the core oligosaccharide of LPS and periplasmic regions in the transporter influence the rate of LPS extraction by LptB2FGC. Together, our genetic data reveal a path for bidirectional coupling between LptB2 and LptFG that extends from the cytoplasm to the entrance to the periplasmic bridge of the transporter. [ABSTRACT FROM AUTHOR]

The threat of free-riding makes the marshalling of cooperation from group members a fundamental challenge of social life. Where classical social science theory saw the enforcement of moral boundaries as a critical way by which group members regulate one another's self-interest and build cooperation, moral judgments have most often been studied as processes internal to individuals. Here we investigate how the interpersonal expression of positive and negative moral judgments encourages cooperation in groups and prosocial behavior between group members. In a laboratory experiment, groups whose members could make moral judgments achieved greater cooperation than groups with no capacity to sanction, levels comparable to those of groups featuring costly material sanctions. In addition, members of moral judgment groups subsequently showed more interpersonal trust, trustworthiness, and generosity than all other groups. These findings extend prior work on peer enforcement, highlighting how the enforcement of moral boundaries offers an efficient solution to cooperation problems and promotes prosocial behavior between group members. [ABSTRACT FROM AUTHOR]

In this reply, we reiterate the main point of our 2012 paper, which was that the measure of inequality used by Norton and Ariely (2011) was too difficult for it to yield meaningful results. We describe additional evidence for this conclusion, and we also challenge the conclusion that political differences in perceived and desired inequality are small. [ABSTRACT FROM AUTHOR]

The article discusses the research on the evolution of cooperation in static and dynamic ties or networks. The findings of the research state that static ties cooperate in the presence of dynamic networks. Topics discussed include student participants divided into static, dynamic, and mixed networks, measuring ties in real-world networks and the use of Prisoner's Dilemma game to measure decision making process.

Humans' propensity to cooperate is driven by our embeddedness in social networks. A key mechanism through which networks promote cooperation is clustering. Within clusters, conditional cooperators are insulated from exploitation by noncooperators, allowing them to reap the benefits of cooperation. Dynamic networks, where ties can be shed and new ties formed, allow for the endogenous emergence of clusters of cooperators. Although past work suggests that either reputation processes or network dynamics can increase clustering and cooperation, existing work on network dynamics conflates reputations and dynamics. Here we report results from a large-scale experiment (total n = 2,675) that embedded participants in clustered or random networks that were static or dynamic, with varying levels of reputational information. Results show that initial network clustering predicts cooperation in static networks, but not in dynamic ones. Further, our experiment shows that while reputations are important for partner choice, cooperation levels are driven purely by dynamics. Supplemental conditions confirmed this lack of a reputation effect. Importantly, we find that when participants make individual choices to cooperate or defect with each partner, as opposed to a single decision that applies to all partners (as is standard in the literature on cooperation in networks), cooperation rates in static networks are as high as cooperation rates in dynamic networks. This finding highlights the importance of structured relations for sustained cooperation, and shows how giving experimental participants more realistic choices has important consequences for whether dynamic networks promote higher levels of cooperation than static networks. [ABSTRACT FROM AUTHOR]

Gram-negative bacteria possess an outer membrane (OM) containing lipopolysaccharide (LPS). Proper assembly of the OM not only prevents certain antibiotics from entering the cell, but also allows others to be pumped out. To assemble this barrier, the seven-protein lipopolysaccharide transport (Lpt) system extracts LPS from the outer leaflet of the inner membrane (IM), transports it across the periplasm and inserts it selectively into the outer leaflet of the OM. As LPS is important, if not essential, in most Gram-negative bacteria, the LPS biosynthesis and biogenesis pathways are attractive targets in the development of new classes of antibiotics. The accompanying paper (Simpson BW, May JM, Sherman DJ, Kahne D, Ruiz N. 2015 Phil. Trans. R. Soc. B 370, 20150029. (doi:10.1098/rstb.2015.0029)) reviewed the biosynthesis of LPS and its extraction from the IM. This paper will trace its journey across the periplasm and insertion into the OM. [ABSTRACT FROM AUTHOR]

Recent work shows that both reward and punishment systems increase short-term cooperation in social dilemmas. Yet, a growing body of research finds that punishment systems generate a range of negative side effects, including an undermining of trust in fellow group members’ cooperative intentions. The present work asks whether reward systems can generate the same positive effects as punishment systems (increased cooperation) without the negative side effects (decreased interpersonal trust) or whether reward systems also lead to detrimental effects on trust. In two experiments we find that once removed, reward systems, like punishment systems, reduced trust to levels below a control group who never experienced sanctions. This research highlights the detrimental effects of punishment and reward systems on intragroup trust and thus shows that while reward systems can generate the same positive effects as punishment systems, they also generate the same negative side effects. [ABSTRACT FROM PUBLISHER]

This paper reports results of an experiment on the relationship between whites’ implicit racial bias and prosocial behavior toward blacks. We hypothesized that implicit anti-black bias would lead to less prosocial behavior (generosity with limited monetary resources). Consistent with our hypothesis, the results revealed that implicit anti-black bias, measured by the Implicit Association Test, had a negative effect on generosity toward blacks. This finding extends prior work by showing that implicit racial bias affects non-hypothetical decisions about how to allocate limited monetary resources. We conclude with a discussion of implications and suggestions for future work. [Copyright &y& Elsevier]

Social order is possible only if individuals forgo the narrow pursuit of self-interest for the greater good. For over a century, social scientists have argued that sympathy mitigates self-interest and recent empirical work supports this claim. Much less is known about why actors experience sympathy in the first place, particularly in fleeting interactions with strangers, where cooperation is especially uncertain. We argue that perceived interdependence increases sympathy towards strangers. Results from our first study, a vignette experiment, support this claim and suggests a situational solution to social dilemmas. Meanwhile, previous work points to two strong individual-level predictors of cooperation: generalized trust and social values. In Study Two we address the intersection of situational and individual-level explanations to ask: does situational sympathy mediate these individual-level predictors of cooperation? Results from the second study, a laboratory experiment, support our hypotheses that sympathy mediates the generalized trust–cooperation link and the relationship between social values and cooperation. The paper concludes with a discussion of limitations of the present work and directions for future research. [ABSTRACT FROM AUTHOR]

The new millennium opens the third decade of work on network exchange theory. During two decades of continuous growth, the program has been tested as intensively and extensively as any in sociology. This article summarizes existing research and describes new directions. First, we describe basic network connections and recently discovered structural power conditions that sharply affect exchange ratios. Then we show how game theory enhances understanding of collective action in exchange networks. Two new research programs link network exchange theory to status characteristics theory: the first demonstrates that power produces status, and the second shows how status value produces power. Finally, we discuss how questions about network dynamics, complexity, and legitimation define paths for future theory growth. [ABSTRACT FROM AUTHOR]