Music is a universal feature of human cultures, and it has both fascinated and troubled many researchers. In this paper we show through the dictator game (DG) that an individual's listening to preferred "chill-inducing" music may promote altruistic behavior that extends beyond the bounds of kin selection or reciprocal altruism. Participants were 22 undergraduate and postgraduate students who were divided into two groups, the in-group and the out-group, and they acted as dictators. The dictators listened to their own preferred "chill-inducing" music, to music they disliked, or to silence, and then played the DG. In this hypothetical experiment, the dictators were given real money (which they did not keep) and were asked to distribute it to the recipients, who were presented as stylized images of men and women displayed on a computer screen. The dictators played the DG both before and after listening to the music. Both male and female dictators gave more money after listening to their preferred music and less after listening to the music they disliked, whereas silence had no effect on the allocated amounts. The group to which the recipient belonged did not influence these trends. The results suggest that listening to preferred "chill-inducing" music promotes altruistic behavior.

When people state their willingness to pay for something, the amount usually differs from the behavior in a real purchase situation. The discrepancy between a hypothetical answer and the real act is called hypothetical bias. We investigated neural processes of hypothetical bias regarding monetary donations to public goods using fMRI with the hypothesis that amygdala codes for real costs. Real decisions activated amygdala more than hypothetical decisions. This was observed for both accepted and rejected proposals. The more the subjects accepted real donation proposals the greater was the activity in rostral anterior cingulate cortex-a region known to control amygdala but also neural processing of the cost-benefit difference. The presentation of a charitable donation goal evoked an insula activity that predicted the later decision to donate. In conclusion, we have identified the neural mechanisms underlying real donation behavior, compatible with theories on hypothetical bias. Our findings imply that the emotional system has an important role in real decision making as it signals what kind of immediate cost and reward an outcome is associated with.

Partner choice promotes competition among individuals to be selected as a cooperative partner, a phenomenon referred to as competitive altruism. We explored whether chimpanzees engage in competitive altruism in a triadic Ultimatum Game where two proposers can send offers simultaneously or consecutively to a responder who can only accept one of the two competing offers. In a dyadic control condition only one proposer at a time could send an offer to the responder. Chimpanzees increased their offers across trials in the competitive triadic, but not in the dyadic control condition. Chimpanzees also increased their offers after being rejected in previous triadic trials. Furthermore, we found that chimpanzees, under specific conditions, outcompete first proposers in triadic consecutive trials before the responder could choose which offer to accept by offering more than what is expected if they acted randomly or simply offered the smallest possible amount. These results suggest that competitive altruism in chimpanzees did not emerge just as a by-product of them trying to increase over previous losses. Chimpanzees might consider how others' interactions affect their outcomes and engage in strategies to maximize their chances of being selected as cooperative partners.

Prokaryotes harbor a variety of genetic replicators, including plasmids, viruses, and chromosomes, each having different effects on the phenotype of the hosting cell. Here, we propose a classification for replicators of bacteria and archaea on the basis of their horizontal-transfer potential and the type of relationships (mutualistic, symbiotic, commensal, or parasitic) that they have with the host cell vehicle. Horizontal movement of replicators can be either active or passive, reflecting whether or not the replicator encodes the means to mediate its own transfer from one cell to another. Some replicators also have an infectious extracellular state, thus separating viruses from other mobile elements. From the perspective of the cell vehicle, the different types of replicators form a continuum from genuinely mutualistic to completely parasitic replicators. This classification provides a general framework for dissecting prokaryotic systems into evolutionarily meaningful components.

In social environments, decisions not only determine rewards for oneself but also for others. However, individual differences in pro-social behaviors have been typically studied through self-report. We developed a decision-making paradigm in which participants chose from card decks with differing rewards for themselves and charity; some decks gave similar rewards to both, while others gave higher rewards for one or the other. We used a reinforcement-learning model that estimated each participant's relative weighting of self versus charity reward. As shown both in choices and model parameters, individuals who showed relatively better learning of rewards for charity--compared to themselves--were more likely to engage in pro-social behavior outside of a laboratory setting indicated by self-report. Overall rates of reward learning, however, did not predict individual differences in pro-social tendencies. These results support the idea that biases toward learning about social rewards are associated with one's altruistic tendencies.

We prospectively investigate protective benefits against depression of cortical thickness across nine regions of a Ventral Frontotemporal Network (VFTN), previously associated with spiritual experience. Seventy-two participants at high and low risk for depression (Mean age 41 years; 22-63 years; 40 high risk, 32 low risk) were drawn from a three-generation, thirty-eight year study. FreeSurfer estimated cortical thickness over anatomical MRIs of the brain (Year 30) for each of the nine ROIs. Depression (MDD with SAD-L; symptoms with PHQ; Years 30 and 38) and spirituality (self-report on five phenotypes; Year 35), respectively, were associated with the weighted average of nine regions of interest. VFTN thickness was: 1) positively associated (p<0.01) with two of five spiritual phenotypes, altruism and love of neighbor, interconnectedness at a trend level, but neither commitment nor practice, 2) inversely associated with a diagnosis of MDD (SADS-L Year 30, for any MDD in the past ten years), and 3) prospectively neuroanatomically protective against depressive symptoms (PHQ-9 Year 38) for those at high familial risk.

Altruism is critical for cooperation and productivity in human societies but is known to vary strongly across contexts and individuals. The origin of these differences is largely unknown, but may in principle reflect variations in different neurocognitive processes that temporally unfold during altruistic decision making (ranging from initial perceptual processing via value computations to final integrative choice mechanisms). Here, we elucidate the neural origins of individual and contextual differences in altruism by examining altruistic choices in different inequality contexts with computational modeling and electroencephalography (EEG). Our results show that across all contexts and individuals, wealth distribution choices recruit a similar late decision process evident in model-predicted evidence accumulation signals over parietal regions. Contextual and individual differences in behavior related instead to initial processing of stimulus-locked inequality-related value information in centroparietal and centrofrontal sensors, as well as to gamma-band synchronization of these value-related signals with parietal response-locked evidence-accumulation signals. Our findings suggest separable biological bases for individual and contextual differences in altruism that relate to differences in the initial processing of choice-relevant information.

The question of what motivates people to participate in research is particularly salient in the HIV field. While participation in HIV research was driven by survival in the 1980's and early 1990's, access to novel therapies became the primary motivator with the advent of combination antiretroviral therapy (cART) in the late 1990s. In the HIV cure-related research context, the concept of altruism has remained insufficiently studied.

Blood donation is considered as one of the purest forms of altruism. Plasma donation, in contrast, despite being a similar process, is mostly a paid activity in which donors are compensated for their contribution to the production of therapeutic preparations. This creates a so-called "plasma paradox:" If remuneration is promised for a socially useful effort, volunteers with altruistic motives might be deterred. At the same time, regular plasma donors who pursue the monetary benefits of donation might drop out if remuneration stops. The same controversy can be caught in the messages of most plasma donation companies as well: They promise a monetary reward (MR), and at the same time, highlight the altruistic component of donation. In this study, we tested the assumption that emphasizing the social significance enhances the willingness to donate blood plasma more effectively than either MR or the combination of these two incentives. This had to be rejected since there was no significant difference between the three scenarios. Furthermore, we also hypothesized that individuals might be more motivated to donate plasma if there is a possibility of offering an MR toward other socially beneficial aims. We found an increased willingness to donate in scenarios enabling "double altruism", that is, when donating plasma for therapeutic use and transferring their remuneration to nongovernmental organizations, is an option. We propose relying on double altruism to resolve the plasma paradox, and suggest that it could serve as a starting point for the development of more optimized means for donor recruitment.

Human altruism shaped our evolutionary history and pervades social and political life. There are, however, enormous individual differences in altruism. Some people are almost completely selfish, while others display strong altruism, and the factors behind this heterogeneity are only poorly understood. We examine the neuroanatomical basis of these differences with voxel-based morphometry and show that gray matter (GM) volume in the right temporoparietal junction (TPJ) is strongly associated with both individuals' altruism and the individual-specific conditions under which this brain region is recruited during altruistic decision making. Thus, individual differences in GM volume in TPJ not only translate into individual differences in the general propensity to behave altruistically, but they also create a link between brain structure and brain function by indicating the conditions under which individuals are likely to recruit this region when they face a conflict between altruistic and selfish acts.

Cooperation is one of the most studied paradigms for the understanding of social interactions. Reciprocal altruism -a special type of cooperation that is taught by means of the iterated prisoner dilemma game (iPD)- has been shown to emerge in different species with different success rates. When playing iPD against a reciprocal opponent, the larger theoretical long-term reward is delivered when both players cooperate mutually. In this work, we trained rats in iPD against an opponent playing a Tit for Tat strategy, using a payoff matrix with positive and negative reinforcements, that is food and timeout respectively. We showed for the first time, that experimental rats were able to learn reciprocal altruism with a high average cooperation rate, where the most probable state was mutual cooperation (85%). Although when subjects defected, the most probable behavior was to go back to mutual cooperation. When we modified the matrix by increasing temptation rewards (T) or by increasing cooperation rewards (R), the cooperation rate decreased. In conclusion, we observe that an iPD matrix with large positive reward improves less cooperation than one with small rewards, shown that satisfying the relationship among iPD reinforcement was not enough to achieve high mutual cooperation behavior. Therefore, using positive and negative reinforcements and an appropriate contrast between rewards, rats have cognitive capacity to learn reciprocal altruism. This finding allows to infer that the learning of reciprocal altruism has early appeared in evolution.

Positive psychology is vital in increasing prosocial behavior and reducing bullying. However, limited studies have analyzed the influence of positive personal characteristics on the prosocial behaviors of bystanders in bullying. The present study examined direct and indirect relationships between spirituality, happiness, altruism, and prosocial bystander behavior in bullying. Participants in this study were 685 students from Northwestern Mexico; 51% were male and 49% female, between 12 and 18 years old (M = 14.3 years, SD = 1.68). A structural equation model (SEM) was calculated. The results indicate that happiness and altruism were related to prosocial bystander behavior. Spirituality and happiness have an indirect relationship by increasing prosocial bystander behavior through the positive effects of altruism. The SEM explained 48% of the variance of the prosocial bystander. The implications for improving defensive behavior in bullying and reducing school violence are discussed.

Parochial altruism refers to ingroup favoritism and outgroup hostility and has recently been linked to testosterone. Here, we investigated the neurobiological mechanism of parochial altruism in male soccer fans playing the ultimatum game (UG) against ingroup and outgroup members (i.e., fans of the favorite or of a rivalling team) using functional magnetic resonance imaging. Our results suggest that individual differences in altruistic tendency influence the tendency for parochialism. While altruistic subjects rejected unfair offers independent of team membership, the more self-oriented 'pro-selfs' displayed a stronger ingroup bias and rejected outgroup offers more often. However, during a second session that introduced a team competition the altruists adapted to this parochial pattern. Behavioral strategy was further characterized by dissociable and context-dependent correlations between endogenous testosterone and neural responses in the anterior insula and the ventromedial prefrontal cortex. In sum, the present findings indicate that parochial altruism is shaped by individual differences in testosterone and behavioral strategy. In that way the results are in line with evolutionary theories of both individual and group selection.

Empathy-affective resonance with others' sensory or emotional experiences-is hypothesized to be an important precursor to altruism. However, it is not known whether real-world altruists' heightened empathy reflects true self-other mapping of multi-voxel neural response patterns. We investigated this relationship in adults who had engaged in extraordinarily costly real-world altruism: donating a kidney to a stranger. Altruists and controls completed fMRI testing while anticipating and experiencing pain, and watching as a stranger anticipated and experienced pain. Machine learning classifiers tested for shared representation between experienced and observed distress. Altruists exhibited more similar representations of experienced and observed fearful anticipation spontaneously and following an empathy prompt in anterior insula and anterior/middle cingulate cortex, respectively, suggesting heightened empathic proclivities and abilities for fear. During pain epochs, altruists were distinguished by spontaneous empathic responses in anterior insula, anterior/mid-cingulate cortex and supplementary motor area, but showed no difference from controls after the empathy prompt. These findings (1) link shared multi-voxel representations of the distress of self and others to real-world costly altruism, (2) reinforce distinctions between empathy for sensory states like pain and anticipatory affective states like fear, and (3) highlight the importance of differentiating between the proclivity and ability to empathize.

Knowledge sharing between individuals is a key process for knowledge-intensive organizations to create value and gain a competitive edge. An individual is in the center of a complex set of factors, which are conducive to the knowledge-sharing process. The purpose of this empirical study is to explain the interaction mechanisms between personality and knowledge-sharing behavior and to examine the mediating effects of willingness to share knowledge and subjective norm. The theory of planned behavior, the social exchange theory, and the big five personality traits theory are combined to explain tacit knowledge-sharing behavior. A survey strategy and purposive sampling was applied, and the analysis was conducted on a sample of 288 employees from Croatia working on knowledge-intensive tasks for which high levels of tacit knowledge sharing are characteristic. A standard online questionnaire consisted of items evaluated on a 7-point Likert-scale, ranging from strongly agree (7) to strongly disagree (1). In the structural model, relationships between altruism, willingness, subjective norm, and tacit knowledge sharing were tested. Confirmatory factor analysis with maximum likelihood estimation was performed by using SEM software AMOS version 23. The findings of the study suggest that altruism has a direct impact on tacit knowledge sharing, reaffirming a relationship with knowledge sharing but distinguishing between sharing of different types of knowledge, assessing tacit knowledge sharing as a construct separate from general knowledge sharing. Our findings suggest that willingness to share is a predictive factor of knowledge sharing behavior between employees, having both direct impact on tacit knowledge sharing and being a mediator between the trait of altruism and tacit knowledge sharing. The mediation test also indicates that altruism has an indirect influence on tacit knowledge sharing when subjective norm was a mediator. The findings suggest that personality traits relying on social capital, such as altruism, have more influence on tacit knowledge sharing compared to personality traits that have accentuated intrinsic components. The study contributes to the better understanding of factors stimulating knowledge-sharing behaviors and provides recommendations based on empirical evidence, which may later be applied in the development of knowledge-sharing leadership styles, employee hiring, and auxiliary initiatives.

Perceived cues signaling others' pain induce empathy which in turn motivates altruistic behavior toward those who appear suffering. This perception-emotion-behavior reactivity is the core of human altruism but does not always occur in real-life situations. Here, by integrating behavioral and multimodal neuroimaging measures, we investigate neural mechanisms underlying modulations of empathy and altruistic behavior by beliefs of others' pain (BOP). We show evidence that lack of BOP reduces subjective estimation of others' painful feelings and decreases monetary donations to those who show pain expressions. Moreover, lack of BOP attenuates neural responses to their pain expressions within 200 ms after face onset and modulates neural responses to others' pain in the insular, post-central, and frontal cortices. Our findings suggest that BOP provide a cognitive basis of human empathy and altruism and unravel the intermediate neural mechanisms.

Organisms often cooperate through the production of freely available public goods. This can greatly benefit the group but is vulnerable to the "tragedy of the commons" if individuals lack the motivation to make the necessary investment into public goods production. Relatedness to groupmates can motivate individual investment because group success ultimately benefits their genes' own self-interests. However, systems often lack mechanisms that can reliably ensure that relatedness is high enough to promote cooperation. Consequently, groups face a persistent threat from the tragedy unless they have a mechanism to enforce investment when relatedness fails to provide adequate motivation. To understand the real threat posed by the tragedy and whether groups can avert its impact, we determine how the social amoeba Dictyostelium discoideum responds as relatedness decreases to levels that should induce the tragedy. We find that, while investment in public goods declines as overall within-group relatedness declines, groups avert the expected catastrophic collapse of the commons by continuing to invest, even when relatedness should be too low to incentivize any contribution. We show that this is due to a developmental buffering system that generates enforcement because insufficient cooperation perturbs the balance of a negative feedback system controlling multicellular development. This developmental constraint enforces investment under the conditions expected to be most tragic, allowing groups to avert a collapse in cooperation. These results help explain how mechanisms that suppress selfishness and enforce cooperation can arise inadvertently as a by-product of constraints imposed by selection on different traits.

Human beings are an extraordinarily altruistic species often willing to help strangers at a considerable cost (sometimes life itself) to themselves. But as Darwin noted "… he who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature." Hence, this is the paradox of altruism. Twin studies have shown that altruism and other prosocial behavior show considerable heritability and more recently a number of candidate genes have been identified with this phenotype. Among these first provisional findings are genes encoding elements of dopaminergic transmission. In this article we will review the evidence for the involvement of one of these, the dopamine D4 receptor (DRD4) gene, in shaping human prosocial behavior and consider the methodologies employed in measuring this trait, specific molecular genetic findings and finally, evidence from several Gene × Environment (G × E) studies that imply differential susceptibility of this gene to environmental influences.

Abortive infection, during which an infected bacterial cell commits altruistic suicide to destroy the replicating bacteriophage and protect the clonal population, can be mediated by toxin-antitoxin systems such as the Type III protein-RNA toxin-antitoxin system, ToxIN. A flagellum-dependent bacteriophage of the Myoviridae, ΦTE, evolved rare mutants that "escaped" ToxIN-mediated abortive infection within Pectobacterium atrosepticum. Wild-type ΦTE encoded a short sequence similar to the repetitive nucleotide sequence of the RNA antitoxin, ToxI, from ToxIN. The ΦTE escape mutants had expanded the number of these "pseudo-ToxI" genetic repeats and, in one case, an escape phage had "hijacked" ToxI from the plasmid-borne toxIN locus, through recombination. Expression of the pseudo-ToxI repeats during ΦTE infection allowed the phage to replicate, unaffected by ToxIN, through RNA-based molecular mimicry. This is the first example of a non-coding RNA encoded by a phage that evolves by selective expansion and recombination to enable viral suppression of a defensive bacterial suicide system. Furthermore, the ΦTE escape phages had evolved enhanced capacity to transduce replicons expressing ToxIN, demonstrating virus-mediated horizontal transfer of genetic altruism.

Empathy and prosocial behaviors toward peers promote successful social development and creation of significant long-term relationships, but surprisingly little is known about the maturation of these skills during the period of adolescence. As the majority of studies have used questionnaires or pain observation paradigms, it remains unknown whether the empathic response of adolescents differs from that of adults in a paradigm that is closer to everyday life. In the current study, fMRI was used to examine the neural correlates of social exclusion observation and subsequent prosocial behavior in 20 adolescents (aged 12-17 years) and 20 adults (aged 22-30 years) while playing a ball-tossing game with what they believed to be real individuals. Observing someone being excluded compared to observing equal inclusion of all players elicited a significantly higher activation of the IFG (pars triangularis) in adults compared to adolescents. When given the opportunity to directly help the excluded player during the game, adolescents showed significantly less prosocial behavior than adults, which was underpinned by a significantly lower activity in the right temporoparietal junction, medial/dorsomedial prefrontal cortex and fusiform face area. These findings might indicate that adolescents have a lower propensity to take the victim's perspective and share his or her distress when witnessing social exclusion, which leads to a lower altruistic motivation to help. The factors that could generate what can be interpreted as a downward modulation of empathy during adolescence are discussed.