Supplementary analysis: Influence of the actual existence of socially close protagonists in the lives of participants In the final version, the items 2, 5, 7, 8, 9, 10, 11, 12, 16, 20 (socially close protagonists) and 24, 26, 27, 30, 31, 35, 37, 38, 39, 40 (socially distant protagonists) were assigned to set A; the items 1, 3, 4, 6, 13, 14, 15, 17, 18, 19 (socially close protagonists) and 21, 22, 23, 25, 28, 29, 32, 33, 34, 36 (socially distant protagonists) became part of set B (see last column in S1 Table). It is the soccer world cup and the final match is on TV. I am a big soccer fan and very excited about the game. All of a sudden, a friend of mine who is not feeling well gives me a call and wants to meet up with me right now. What do I do? The results section is structured into two main parts. In the first main part, we present analyses concerning the development and validation of our new 40-items EMCS Scale as well as the development of two parallelized 20-item sets (each ten scenarios with socially close and socially distant protagonists) for future use in within-subjects design studies. For the two parallelized sets A and B, we used Wilks L mvc tests to demonstrate parallelism [ 54]. The procedure by Wilks tests the hypothesis that the means are equal, the variances are equal, and the covariances are equal. The test statistic is based on the weighted differences of the subsample means with the grand mean and the ratio of subsample and complete sample (co)variances, which are shown to be chi 2-distributed when the data meets hypothesis (see [ 54], formula 1.4). Moreover, we report the measurement qualities based on Rasch model analyses and classical test theory fit indices of the complete 40-items EMCS Scale and its two subsets A and B. In our data, we did not observe that the percentage of altruistic decisions differed depending on the social closeness of the protagonists. This is in contrast to the results of Zhan and colleagues [ 31], the only study so far that investigated the impact of social closeness on everyday moral decision-making. Contrary to Zhan et al. [ 31], we only observed a slightly, but not significantly lower percentage of altruistic decisions for the items with socially distant protagonists than for the items with socially close protagonists, and this difference only reached a very small effect size ( d = 0.12). Additionally, Rasch model analyses indicated that there was one underlying latent trait variable, which further speaks against a significant impact of social closeness on everyday moral decision-making in our surveys. This divergent finding could possibly be explained by methodological differences. Since Zhan et al. [ 31] did not provide concrete examples of their stimulus material in their manuscript, it remains unclear whether their vignettes represented everyday moral conflict situations. Furthermore, our data also appear to be in contrast to several abstract moral decision-making studies, which showed that social closeness is an important experimental design parameter in moral dilemma research ([ 5, 28– 30]; see also [ 2]). One potential explanation could be that abstract moral dilemmas describe dead-or-alive situations, whereas the consequences of the response alternatives in our everyday moral dilemmas are less grave. Therefore, one might be more willing to accept the costs of an egoistic response option not only for socially distant others, but also to some degree for socially close persons.

Thus, current moral dilemma research comprises no longer only abstract reasoning about moral dead-or-life situations (e.g., [ 3, 4]) but also research on moral decision-making in a variety of daily life situations (e.g., [ 17, 18]). Applying ecological momentary assessment in a large study sample ( N = 1.252 participants), Hofmann et al. [ 18] repeatedly assessed moral or immoral acts and experiences in everyday life. The authors were able to confirm five areas of human morality (care/harm, fairness/unfairness, loyalty/disloyalty, authority/subversion, and sanctity/degradation) as originally proposed by the Moral Foundations Theory (MFT; [ 19, 20]). Moreover, honesty/dishonesty was the third most frequently mentioned dimension regarding morality in everyday life and, thus, emerged as another important category [ 18, 21]. For humans and most animals, the social interaction with conspecifics is a common everyday life activity [ 1]. Thereby, we humans are often confronted with morally conflicting social interaction situations. According to Christensen and colleagues [ 2], moral conflicts are situations in which someone is pulled in contrary directions by rival moral reasons. They can, amongst others, occur when deciding between a personal interest versus an accepted moral value.I want to sell my old car. I know that the car’s radiator actually needs to be exchanged urgently. A man who does not notice the problem with the radiator offers to pay a good price in cash right away. What do I do? With regard to research in laboratory settings, several scholars (e.g., [ 16, 22, 23]) recently developed everyday moral dilemmas. Everyday moral dilemmas are short vignettes describing hypothetical everyday life situations. The vignettes require decisions between the fulfilment of a moral standard or social obligation towards another person versus a personal-oriented hedonistic behavior that would explicitly not cause serious bodily harm or legal consequences [ 16]. The given response alternatives are typically altruistic (e.g., helping an old woman who is in distress) versus egoistic (e.g., catching the waiting bus home; see [ 23] or [ 24] for further examples).

I have promised my partner to go to the company party with him/her. He/she has already signed both of us up. Now I realize that I would urgently need the time to prepare for an important exam. What do I do?In addition to scale development and validation, we aimed at investigating if everyday moral decision-making depends on the social closeness of the protagonists. As revealed in a recent review, the relatedness of the participant to the story characters is an important experimental design parameter in moral dilemma research [ 2]. Therefore, social closeness could be one further potential modulating factor of everyday moral decision-making (apart from the emotionality of a situation, which has already been examined in previous studies; see [ 22, 23]). Consistently, several studies have shown that both abstract and everyday moral decision-making differ depending on the closeness of the relationship with the target person (e.g., [ 5, 17, 28– 31]). With regard to everyday moral decision-making in laboratory settings, so far only Zhan and colleagues [ 31] investigated the impact of the social closeness of the protagonists. They observed that participants made less altruistic decisions, took more time for their decisions, and rated the situations as emotionally more negative if the moral conflicts involved strangers versus friends and acquaintances. Presuming that altruistic decisions are some kind of generous acts, this finding is also in line with studies in social psychology on social discounting, showing that generosity decreases hyperbolically with increasing social distance between the donor and the recipient [ 32– 37]. Thus, we experimentally varied the social closeness of the protagonists in our scenarios (socially close vs. socially distant) and hypothesized a lower percentage of altruistic decisions for scenarios involving socially distant protagonists as compared to stories involving socially close target persons. Interestingly, we also did not observe gender differences in our surveys, which, on the one hand, is not uncommon for hypothetical moral dilemmas [ 43], but, on the other hand, is in sharp contrast to early moral reasoning research [ 42] and current abstract moral decision-making studies [ 7, 38– 41]. This inconsistent result could potentially be explained by the fact that our new EMCS Scale measures altruistic and egoistic response tendencies, which are behavioral measures that rather reflect outcomes of morality, but not moral attitudes itself [ 43]. Altogether, in combination with the social closeness results, our data therefore point to the idea that everyday moral decision-making with altruistic versus egoistic response options seems to be quite a different construct than abstract moral decision-making with utilitarian versus deontological response alternatives. Furthermore, we did not explicitly control for socially desirable responding in our surveys. Nevertheless, we tried to keep the potential impact of social desirability as low as possible by ensuring strict anonymity to all our participants. Moreover, we excluded all items with extremely high percentages of altruistic decisions. For the remaining items, we observed statistical variance both within participants and across items, which probably speaks against highly socially desirable responding.