The social function of the feeling and expression of guilt

Humans are uniquely cooperative and form crucial short- and long-term social bonds between individuals that ultimately shape human societies. The need for such intense cooperation may have provided a particularly powerful selection pressure on the emotional and communicative behaviours regulating cooperative processes, such as guilt. Guilt is a social, other-oriented moral emotion that promotes relationship repair and pro-sociality. For example, people can be more lenient towards wrongdoers who display guilt than towards those who do not. Here, we examined the social consequences of guilt in a novel experimental setting with pairs of friends differing in relationship quality. Pairs of participants took part in a cooperative game with a mutual goal. We then induced guilt in one of the participants and informed the other participant of their partner's wrongdoing. We examined the outcome using a dictator game to see how they split a joint reward. We found that guilty people were motivated to repair wrongdoing regardless of friendship. Observing guilt in others led to a punishment effect and a victim of wrongdoing punished close friends who appeared guilty more so than acquaintances. We suggest, therefore, that guilt has a stronger function between close friends as the costs of relationship breakdown are greater. Relationship context, therefore, is crucial to the functional relevance of moral emotions.


Comments to the Author(s)
The experimental set-up strikes me as innovative and effective. And the results are interesting, and worth publishing.
Decision letter (RSOS-200617.R0) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
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Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Dr Narayanan Srinivasan (Associate Editor) and Essi Viding (Subject Editor) openscience@royalsociety.org I do have some concerns, which are given below and the authors are requested to address those concerns and submit the final version of the paper.
(1) Abstract makes no mention of the method used. While i know this style is used by some, i find it difficult to understand the result if i have no idea what method was used.
(2) At the end of introduction, authors mention the use of "dictator game". Perhaps a rationale for picking the dictator game can be explicitly provided given that other games are potentially available.
(3) Did the authors have any hypotheses regarding how friendship affects how wrongdoers who are perceived as guilty are treated? Was this study exploratory? (4) It was not clear how the sample size was decided and what was the stopping criteria used, if any? Some information can be provided. (5) It was not clear whether the order of the questionnaires before the subjects played the game was fixed. Supplementary material says order of questions was randomized but it seems to imply that this was within a questionnaire. The URCS seems to come always at the end just before people played the game. Would that affect anything? (6) Page 10 -p = .049. See earlier comment on sample size estimation. (7) Feeling of guilt and shame -Was there any difference between europeans and east asians? was it affected by whether they came as pairs or signed up alone. Majority of subjects seems to have come as pairs. (8) Again, any cultural difference in terms of reward split (page 11) (9) The rationale for median split was not clear to me. Why not use friendship strength as a continuous variable rather than arbitrarily dichotomizing it using median split? What was the distribution of friendship strength? Also it appears that there are outliers influencing the results. There is a subject (green dot, number 15 appears on the side in figure 3) in strong friendship group, who seems a definite outlier and probably is contributing to the effect. Please check whether this is an outlier (visually appears to be the case) and if so, analyze after dropping that subject. There could be other outliers. (10) One issue that is not discussed very well in the discussion is the fact majority of the people are known to each other and that itself may be the reason for less leniency. Authors mention that "Participants were given the opportunity to either sign up with one of their friends or sign up alone and be paired up with a stranger (36 participants signed up alone to be paired up)." Perhaps this is one reason the results are different from other studies, which may have paired up strangers. Perhaps the authors can clarify or discuss this aspect.
Reviewer comments to Author: Reviewer: 1 Comments to the Author(s) The experimental set-up strikes me as innovative and effective. And the results are interesting, and worth publishing.

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Author's Response to Decision Letter for (RSOS-200617.R0)
See Appendix A.

Decision letter (RSOS-200617.R1)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Dr Julle-Danière, It is a pleasure to accept your manuscript entitled "The social function of the feeling and expression of guilt" in its current form for publication in Royal Society Open Science. The comments of the reviewer(s) who reviewed your manuscript are included at the foot of this letter.
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Associate Editor Comments to Author (Dr Narayanan Srinivasan)
I do have some concerns, which are given below and the authors are requested to address those concerns and submit the final version of the paper.
1. Abstract makes no mention of the method used. While i know this style is used by some, i find it difficult to understand the result if i have no idea what method was used.
Thank you, we added a sentence regarding the Method used ll.20-23.
2. At the end of introduction, authors mention the use of "dictator game". Perhaps a rationale for picking the dictator game can be explicitly provided given that other games are potentially available.
A rationale for using the dictator game is now presented in the 'Measures' section (ll.184-189) but we thank you for your comment and have added a short explanation for choosing this game in the introduction (ll.86-89).
3. Did the authors have any hypotheses regarding how friendship affects how wrongdoers who are perceived as guilty are treated? Was this study exploratory?
This study was indeed exploratory and as such, we did not have hypothesis regarding the effect of friendship. Based on previous studies, we could have expected guilty wrongdoers to be treated more leniently, but as friendship had never been investigated in this context, we did not formulate hypotheses.
4. It was not clear how the sample size was decided and what was the stopping criteria used, if any? Some information can be provided.
Thank you for pointing this out. The sample size for this study was based on previous research looking at the induction of guilt. We could not run a power analysis prior to the study as we did not know the effect of the factors investigated and could not use previous research to estimate those. Moreover, due to financial limitation, and to keep the design as simple as possible, we did not include a 'no guilt' condition for Player 1. This allowed us to minimise the number of variables, already extensive, and reduce the number of participants needed. Therefore, in order to capture as many facial expressions as we could in a culturally varied sample, we aimed to have 50 to 60 participants posing as Player 1 in each condition (2 conditions for Player 1: 'blame' vs. 'no blame').
As a result, we aimed to collect data from 110 pairs of participants. This information has been added to the manuscript (ll. 97-103).
5. It was not clear whether the order of the questionnaires before the subjects played the game was fixed. Supplementary material says order of questions was randomized but it seems to imply that this was within a questionnaire. The URCS seems to come always at the end just before people played the game. Would that affect anything?
Thank you for your comment, this has been clarified in the Sup. Mat. ll.35-36. The order of questionnaires was indeed fixed within blocks throughout the experiment. We did not expect the order presentation to influence participants responses or reactions to the game, but if the order did impact the participants, the impact would be the same for all. As participants were only tested once, we did not consider this to be an issue for our experiment.
This p value is very close to non-significance and we try to acknowledge that and exercise caution throughout. As this is an exploratory study, more research is needed to help understand the effect of the guilt induction on Player 1's feelings.
7. Feeling of guilt and shame -Was there any difference between europeans and east asians? was it affected by whether they came as pairs or signed up alone. Majority of subjects seems to have come as pairs. 8. Again, any cultural difference in terms of reward split (page 10) Thank you for your comment. Culture was not a factor of interest in this study. Our sample included participants that self-identified as belonging to either a European or an (East-)Asian ethnicity, but we emphasise this as a non-WEIRD sample and thus more representative. We were interested in holistic results, but we acknowledge that it is a very interesting question that would require further research. Most participants did sign up as pairs, but the closeness/friendship questionnaire revealed that this was not an indicator of objective closeness. Indeed, some participants that came as a pair met their partner a few weeks prior to the study (first year students starting University late September, study running from December to April) and did not feel particularly close to them. Therefore, we considered the friendship index a more objective factor to investigate rather than splitting our sample between pairs that signed up together and pairs that were randomly formed. The level of friendship did not affect the self-reported feelings (Sup Mat ll. 187-188).
9. The rationale for median split was not clear to me. Why not use friendship strength as a continuous variable rather than arbitrarily dichotomizing it using median split? What was the distribution of friendship strength?
Thank you for your comment, we hope that the following explanation will clarify this point. Despite not being able to split our sample by pair type (see above), our recruitment practice still resulted in a bimodal distribution: participants were invited to either sign up with a friend or alone. Therefore, as shown in the histogram below, the friendship index distribution was bimodal: many people are not friends, and many are strong friends (5-7), but fewer people are in between. We could have just trusted the fact that 'friends' signed up together, but we wanted to double check using this median split method.
The friendship index was controlled for in the bootstrapping analysis and the median split was used to ensure that friends and non-friends were distributed equally when testing other conditions, as explained in the Supplementary Materials ll. 125-128: "The bootstraps were conducted so that the ratio of the two places of origin and the two friendship categories (weak friendship: if one or both players reported a friendship index 4<; strong friendship: both players reported a friendship index ≥ 4) in the null condition were identical with the ratio in the test condition, to avoid results being driven by different underlying group structures.". This did not impact the results of the bootstrapping analysis in any way but was a necessary step to ensure that there was no systematic difference in group structure between the null condition and our datasets.
For consistency purposes, we used the bimodal variable in all the analyses conducted (bootstrap and GLM).
Also it appears that there are outliers influencing the results. There is a subject (green dot, number 15 appears on the side in figure 3) in strong friendship group, who seems a definite outlier and probably is contributing to the effect. Please check whether this is an outlier (visually appears to be the case) and if so, analyze after dropping that subject. There could be other outliers.
We agree that some extreme values could be influencing the fit of our models. In addition to the 'number 15' datapoint, 9 more datapoints could be considered extremes (or, outliers), appearing more than 1.5 standard deviations from our mean. However, we are hesitant to remove these from our dataset and analysis for several reasons. These datapoints represent authentic decisions made by our participants (as opposed to an error in measurement) and reflect legitimate responses made by our participants in our scenario. GLM's are quite robust to non-normal distributions, and therefore we do not believe we have justification to remove these points entirely. Our analysis is also sensitive to smaller sample sizes. We admit our sample-size is already on the lower end, and therefore if we removed these extremes that would account for more than 10% of our data, which could make our findings less (rather than more) robust.
We do, however, agree that if there are any datapoints that are significantly influencing the fit of our models, we should then approach our findings with much more caution. If we refit our data excluding the 'number 15' datapoint, or, by removing all values more than 1.5SD, the interaction between Friendship and Judged Guilt does not hold (ß = 0.03; SE = 0.025, p < 0.15 and ß = 0.02; SE = 0.014, p < 0.14 respectively). We do not believe this invalidates our original findings, but this does suggest that our models are not overly robust. We now discuss this transparently in our results, and emphasise the added caution we should take because of this (ll. 249-253) : "To assess the robustness of this model, we reran the analysis without any extreme values (i.e, outliers; any value >1.5SD from the mean, n=10). This interaction did not hold with the removal of these data points; either potentially due to extreme values driving the model, or, due to the reduction in sample size. We therefore want to highlight this finding should be approached with caution." 10. One issue that is not discussed very well in the discussion is the fact majority of the people are known to each other and that itself may be the reason for less leniency. Authors mention that "Participants were given the opportunity to either sign up with one of their friends or sign up alone and be paired up with a stranger (36 participants signed up alone to be paired up)." Perhaps this is one reason the results are different from other studies, which may have paired up strangers. Perhaps the authors can clarify or discuss this aspect.
Thank you, we have included this point in the discussion (ll.334-337).