Development of MPFC function mediates shifts in self-protective behavior provoked by social feedback

How do people protect themselves in response to negative social feedback from others? How does such a self-protective system develop and affect social decisions? Here, using a novel reciprocal artwork evaluation task, we demonstrate that youths show self-protective bias based on current negative social evaluation, whereas into early adulthood, individuals show self-protective bias based on accumulated evidence of negative social evaluation. While the ventromedial prefrontal cortex (VMPFC) mediates self-defensive behavior based on both current and accumulated feedback, the rostromedial prefrontal cortex (RMPFC) exclusively mediates self-defensive behavior based on longer feedback history. Further analysis using a reinforcement learning model suggests that RMPFC extending into VMPFC, together with posterior parietal cortex (PPC), contribute to age-related increases in self-protection bias with deep feedback integration by computing the discrepancy between current feedback and previously estimated value of self-protection. These findings indicate that the development of RMPFC function is critical for sophisticated self-protective decisions.


Supplementary Note 1. Post-experimental questionnaires designed to assess participant-specific task experience.
For exploratory purpose, we measured each participant's interest, effort, selfevaluation, and expected other-evaluation immediately following the Artwork creation task. The exact questions include: 1) "How interesting was this activity? [0 (not interesting at all) -10 (very interesting)]," 2) "How much effort did you put on this To ensure that the minor raters (N = 45) were not insensitive to the creativity of artworks determined by the independent adult raters, we ran a repeated measures ANOVA with an independent variable of 5 levels of OC determined by the independent adult sample and a dependent variable of proportion of favorable evaluation. The result showed a robust effect of OC on the evaluation of the artworks (F(4, 41) = 41.905, p < 0.001), suggesting that the minor participants were sensitive to the creativity of artworks, similarly to the independent adult group.

Supplementary Note 3. Post-experimental questionnaires indirectly probing
suspicion about the purpose of the study.
To assess whether the participants were aware of the purpose of the study or not, we asked the participants to answer the following post-experimental questions: 1) "Write down your thoughts and feelings during the task freely." 2) "How did you feel when the partner evaluated your artwork not creative? [0 (I didn't feel bad at all) -5 (I felt very

Supplementary Note 4. Measurement of task-related personality trait variables.
We measured various personality trait variables that are potentially related to the behavioral outcomes in the Artwork evaluation task. First, we asked how important it is for them to be creative in general [1 (Not important at all) -6 (Very important)], which would indicate individual differences in the perceived significance of the trait of creativity.
Second, participants reported approval need and trait self-esteem using a 20-item of the Revised Martin-Narsen Approval Motivation Scale (RMLAM) 1 and a 10-item of the Rosenberg Self-Esteem Scale 2 .
Supplementary Note 5. Details in task structure of the independent adult-only study distinguished from those of the main developmental study.

1) The Reciprocal Artwork Evaluation Task included a total of 99 trials
(including those artworks with large between-rater variability): 35 positive feedback trials, 35 negative feedback trials, and 29 neutral feedback trials. 2) The presentation order of all the condition trials was fully randomized such that every participant experienced a unique sequence of the condition trials, which were determined by specific combinations of feedback valence types and OC levels.

Supplementary Note 6. The examples of the younger participants' answers to the
opened-questions during the debriefing asking emotional experience when receiving negative feedback from partners.
"I felt bad because I believe people did not see my artwork in detail.", "I felt bad because I received negative evaluations despite the large effort", "I felt bad as it is usual to feel bad when receiving negative words about one's own work", "I couldn't feel good enough when receiving negative evaluation.", "It was frustrated that some people did not acknowledge my effort", "I felt very bad and irritated", "Although I knew that I didn't do very well, I did not feel good with negative evaluation.", "I felt somewhat bad because some people gave me negative evaluation even though they also did not do well", "I thought some people might not have seen my artwork in detail and gave me negative evaluation, because I drew the artwork very elaborately.", "I felt good because many people gave me good evaluation, but I felt somewhat bad because some people gave me negative evaluation", "I also thought my artwork was not that creative. As it was my artwork, however, I felt somewhat bad when receiving negative evaluation."