1. Introduction

For centuries, economists and psychologists have argued that moral emotions stimulate prosocial behavior. Prosocial behavior refers to the broad range of actions intended to benefit one or more people other than oneself ^[1] (p. 463). The field of prosociality is flourishing. However, researchers do not always agree on a common definition of prosocial behavior and often neglect to define it altogether. Common to almost all definitions is an emphasis on promoting well-being in agents other than the actor. For an overview of the breadth of definitions of prosocial behavior and the related concept of altruism and helping behavior, readers are referred to the review by Pfattheicher et al. ^[2] in which the authors show how definitions of these concepts differ in whether they emphasize intentions and motivations, costs and benefits, and social context. The literature shows that guilt, as a moral emotion, does motivate prosocial behavior in dyadic social dilemma situations [3,4,5,6]^[3][4][5][6]. However, de Hooge et al. ^[7] claimed that in social situations involving multiple individuals the moral and prosocial nature of guilt is questionable. In these circumstances, indeed, guilt can produce positive consequences for the victim of one’s actions but disadvantageous effects for others in the social environment. For example, it might be considered moral behavior to spend more time with a hurt loved one at the expense of one’s own time. However, as de Hooge et al. ^[7] point out, while guilt may lead to an extra investment in that relationship, another person will have to pay the cost for this. Building of de Hooge et al.’s ^[7] claim that in social situations involving multiple individuals the prosocial nature of guilt is questionable.

2. Interpersonal Effects of Guilt

The literature that addresses guilt attributes this feeling to an emotion characterized by a negative tone elicited when a person perceives that their behavior has violated moral standards or has caused harm to others [12,13,14]^[8][9][10]. These are cases in which the actor has intentionally or unintentionally injured another person [15,16]^[11][12]. The agents are concerned about bad behavior and experience a lot of cognitive rumination [14,17]^[10][13]. Guilt has been described as a source of oppression and self-flagellation that may lead to unbearable feelings of self-loathing and despair, and mental illness. Individuals high on guilt may feel worthless and deserve punishment [14]^[10]. Depression and guilt are both characterized by intropunitive traits and share common antecedents. Greater guilt is associated with more significant depression and with symptoms of obsessive-compulsiveness, anxiety, somatization, and psychoticism [18,19]^[14][15]. In the field of moral emotions, psychological theory and research distinguish between guilt and shame. Shame is an emotion typically experienced after failures, inadequacies, and moral or social transgressions [20]^[16]. More specifically, it is experienced when people fail to live up to moral or social standards and when others are aware—or might be aware—of this failure. When people experience shame, they think of others who disapprove of them or who will evaluate them negatively. Shame is an emotion that leads to self-reflection: it is associated with an awareness of feeling small, worthless, and incompetent [20,21]^[16][17]. Further, shame is related to the tendency to withdraw and isolate oneself [3,22]^[3][18]. In contrast to shame, guilt focuses on specific behavior and does not generalize into a negative image of the whole self [16,23]^[12][19]. Tangney et al. [24]^[20] found that when referring to shame-inducing situations, respondents were more concerned with others’ evaluations of the self. In contrast, respondents were more concerned with their effect on others when describing guilt situations. This difference in egocentric versus other-oriented concerns is not unexpected, given that shame contains a focus on the self while guilt relates to a specific behavior [25]^[21]. Differences can be identified in the neural basis of these emotions, as shame and guilt are related to activity in brain regions involved in social cognition and emotion regulation. However, they have distinct neural circuits that can be differentiated based on social evaluation [26]^[22]. Opposed theoretical positions and empirical findings are seen in work examining the role of guilt in prosocial behavior. Indeed, shame has been theorized and empirically shown to be a negative feeling with many positive consequences [4,6,16,27,28,29]^{[4][6][12][23][24][25]}. For example, guilt theories assume that this emotion stimulates a better grasp of perspective and feelings of empathy [16,30]^[12][26]. A great deal of literature also suggests that guilt motivates people to make amends and redress their actions [3,24,31,32,33,34]^{[3][20][27][28][29][30]}. Many researchers demonstrated that individuals who were induced to feel guilty were more willing to help others than those who were not influenced to feel guilty [35,36,37]^[31][32][33]. Guilt encourages behaviors that aim to restore the relationship between transgressor and victim or prevent damage to this relationship [16,38,39]^[12][34][35]. In general, guilt is considered an exemplary moral emotion, motivating prosocial behavior and strengthening social bonds [3,40,41]^[3][36][37]. Economists have also addressed the guilt. Although they start from a self-centered view of the individual, they are also inclined to recognize that guilt has the advantage of holding back those personal, self-centered tendencies instead of stimulating prosocial action [42,43,44]^[38][39][40]. For example, Ketelaar and Au ^[4] have shown that people who feel guilty after defecting in a social dilemma game tend to cooperate more in further repetitions of the game. Hopfensitz and Reuben [45]^[41] found that someone who is punished for defecting will only not retaliate in the future if they feel guilty or ashamed. More generally, behavior following guilt is usually interpreted as moral behavior or behavior motivated by concern for another person [35,46]^[31][42]. Therefore, guilt is often presented as a moral emotion that is associated with the well-being of society, and that encourages people to think about how their behavior affects the well-being of other people [3,6]^[3][6] Recent studies on the impact of emotions on prosocial behavior in dyadic relationships are the most direct evidence of the moral effects of guilt. These studies demonstrate that people who feel guilty or anticipate guilt act prosocially towards others when engaged in games involving social dilemmas [4,47,48,49,50]^{[4][43][44][45][46]}. Thus, in dyadic contexts, despite its negative tone, guilt plays a functional role in protecting interpersonal relationships, leading people to place others’ concerns before their own [3,29]^[3][25]. The social psychology literature abounds with models explaining the psychological factors underlying the relationship between guilt and prosocial behavior. The main models that enjoy the most significant empirical consideration are the following:

• The desire to repair the specific wrong [51]^[47]: A state of guilt causes the formation of a desire to repair the particular perceived wrong performed by the agent, which in turn motivates helpful behavior aimed at repairing the fault.
• The desire to repair wrong-doing as such [12,52]^[8][48]: This model posits that the motivation driving prosocial behavior is not so much a desire to right the specific wrong done but, rather, a more general desire to repair responsibility for a wrong as such.
• The desire to improve one’s standing [53,54]^[49][50]: The previous model posited a desire, which is not directly concerned with the agent in question, but instead with morality itself and the importance of repairing a failure to live up to the agent’s moral standards. To help explain the relationship between guilt and helping, it can be instead posited a potential desire on the part of the agent to improve their (actual or perceived) moral purity, worth, virtue, social image, social attachments, social and communal relationships, moral standing in the community, or the like.
• The desire to alleviate one’s guilt [12,^[855]^][51]. The fourth model to be mentioned here holds that guilt states often cause the formation of a desire to eliminate or reduce the agent’s guilt. Since helping is one widespread way of making oneself feel better and no longer guilty about a prior wrong act, it is only to be expected that guilt would be positively correlated with helping, other things being equal. In this picture, then, helping is treated as an instrumental means for promoting the agent’s subjective well-being.

Beyond the factors underlying the relationship between guilt and prosocial behavior, guilt theories agree on seeing positive consequences for the well-being of others in feelings of guilt. This image of guilt is best summed up in the fact that a sense of guilt is “an adaptive emotion, which benefits individuals and their relationships in various ways” [40,56,57]^[36][52][53].