The Influence Of Bystanders On Perception Of Unfairness And Related Decision Making

As a kind of basic social norms,the fairness norm is a behavioral criterion that everyone should obey in social life.When the fairness norm is violated,individuals would experience feelings of unfairness,and even exhibit some ―irrational‖ behaviors which deviate from the goal of maximizing their personal benefits.For example,in the economic decision-making tasks,individuals may sacrifice their own interests to punish norm violators.Researchers often use the ultimatum game(UG)task to study unfairness-related issues in laboratory conditions.This task contains a proposer and a responder.The proposer is entitled to decide how to split a sum of money and the responder need to decide to accept or reject the division schema.Acceptance means both of the proposer and the responder will get the suggested split,while rejection means both of them get nothing.Based on this paradigm,researchers found that individuals’ perceived unfairness was not invariable.Their feelings of unfairness and related decision-making processes may be modulated by various factors from proposers,responders or other aspects.Individuals always live in social groups.When they encounter unfair events and need to make responses to the unfair treatments towards them,the events may be exposed to others,who could observe these events as a bystander or even express their attitudes towards these events.Prior studies have demonstrated that,the presence of others and others’ attitudes would influence people’s minds and behaviors.Will individuals’ feelings of unfairness and related decision-making be affected by bystander factors(e.g.,whether there are the bystanders at present or which kind of attitudes they express)? How are the underlying brain activation patterns modulated by bystander factors? Few studies have tried to answer these questions systematically.Based on the classical UG task,the present study manipulated three different bystander factors,that is,whether there are the bystanders at present,whether there are social supports from bystanders and whether there are social pressures from bystanders,and investigated the impact of these bystander factors on individuals’ feelings of unfairness and related decision-making.In addition,the present study also used the fMRI technique to probe brain mechanisms underlying the modulation processes.Three studies(totally 7 experiments)were designed.Based on the classical UG task,study 1 manipulated whether there were bystanders at present or not(with no attitude expression)during responders playing with proposers.Experiment 1a(behavioral study)and Experiment 1b(fMRI study)were carried out to explore the impact of the presence of bystanders on responders’ feelings of unfairness and related decision-making processes from both behavioral and neural levels.Study 2 also included two experiments.Experiment 2a(behavioral study)and Experiment 2b(fMRI study)were carried out to explore the impact of social supports from bystanders on responders’ feelings of unfairness and related decision-making processes from both behavioral and neural levels.Study 3 included three experiments.Experiment 3a(behavioral study),Experiment 3b(behavioral study)and Experiment 3c(fMRI study)were performed to probe the impact of social pressures from bystanders on responders’ unfairness perception and related decision-making processes from both behavioral and neural levels.The behavioral results showed that responder’s fairness ratings were significantly lower in the unfair trials than in the fair trials,no matter whether there were bystanders or which kind of attitudes bystanders expressed.And the responder’s rejection rates for fair fairs were nearly zero.However,the responder’s rejection rates for unfair trials were rather high(the rejection rates were 40% and above).These results indicated that individuals’ perceptions of violations of the fairness norm were relatively stable.Facing the unfair behaviors,people would sacrifice their own interests to punish the violators and enforce the fairness norm.Compared to the conditions without the presence of bystanders or the presence of social supports from bystanders,the responders’ fairness ratings were lower and rejection rates were higher for unfair trails when there were bystanders or there were social supports from bystanders.These results suggested that the presence of bystanders or the presence of social supports from bystanders made people become more sensitive to violations of the fairness norm,and more willing to reject the unfair distributions.Under social pressures from bystanders,both men and women experienced a higher level of unfairness feelings and maintained a higher rejection rate in unfair trials relative to fair trials.Meanwhile,fairness ratings of unfair trials in men were lower and men were more inclined to reject the unfair distributions under social pressures.However,fairness ratings of unfair trials in women were not influenced by social pressures from bystanders.Under social pressures from proposer’s friends,rejection rates of unfair trials in women were lower.These results indicated that women’s sensitivity to fairness norm violations was stable and their tolerance for others’ unfair behaviors was rather high.Analyses on fMRI data showed that,anterior insula was more active during unfair relative to fair trials.Along with increased unfairness feelings caused by bystander factors,enhanced activations in anterior insula and dorsal anterior cingulate cortex were also observed at the neural level.When there were bystanders or there were social supports from bystanders,anterior insula was more active during rejecting relative to accepting unfair offers.For men,increased anterior insula activation and anterior insula-dorsal anterior cingulate cortex functional connectivity were observed during unfair relative to fair trials under social pressures from bystanders,but not in the context without social pressures from bystanders.Meanwhile,dorsolateral prefrontal cortex was related to rejection behaviors under social pressures from bystanders.In women,the behavioral difference between two social pressure contexts was predicted by pregenual anterior cingulate cortex activation difference between two contexts when they accepted unfair offers.This paper explored the influence of bystander factors on feelings of unfairness and related decision-making processes from both behavioral and neural levels.The results showed the presence of bystanders and attitudes of bystanders indeed influenced individual’s feelings of unfairness and related decision-making processes.These results are beneficial for a deeper understanding of unfairness perception and related decision-making processes in complex social situations.