Beyond self-serving bias: diffusion of responsibility reduces sense of agency and outcome monitoring

Abstract

Diffusion of responsibility across agents has been proposed to underlie decreased helping and increased aggression in group behaviour. However, few studies have directly investigated effects of the presence of other people on how we experience the consequences of our actions. This EEG study investigated whether diffusion of responsibility simply reflects a post-hoc self-serving bias, or rather has direct effects on how we process the outcomes of our actions, and our experience of agency over them. Participants made voluntary actions whose outcomes were more or less negative. Presence of another potential agent reduced participants' sense of agency over those outcomes, even though it was always obvious who caused each outcome. Further, presence of another agent reduced the amplitude of feedback-related negativity evoked by outcome stimuli, suggesting reduced outcome monitoring. The presence of other agents may lead to diffusion of responsibility by weakening the neural linkage between one's actions and their outcomes.

Keywords: FRN; diffusion of responsibility; outcome monitoring; sense of agency; social interaction.

Fig. 1.

Marble task. Figure shows the outline of a low-risk successful trial (A), a high-risk successful trial (B), and an unsuccessful trial (C). Note that C is the worst outcome, B the best, and A the intermediate. Social context was indicated at the start of a trial, by either presenting the participant’s own avatar alone, or together with the other player’s avatar. The marble colour served as a reminder of social context, and was either blue in the alone condition (shown here), or green in the together condition. In the together condition, besides the trials displayed here, there were trials in which the ‘other’ player stopped the marble, and the participant did not lose any points. ERPs were time-locked to outcome presentations of successful trials (A and B, marked in bold) in which the participant stopped the marble.

Fig. 2.

Behavioural results. (a) Parameter estimates for the model predicting agency ratings, with 95% bootstrapped confidence intervals. Condition refers to the effect of social context (Alone = 0 vs Together = 1), such that a negative parameter estimate denotes a loss of agency in the Together condition. (b) Mean agency ratings for the two experimental conditions, showing a significant reduction in agency ratings in Together trials. (c) Mean position at which participants stopped the marble for the two experimental conditions, showing a significant delay of actions in Together trials. Error bars show standard error of the mean.

Fig. 3.

ERPs. Grand average time courses are shown for the two experimental conditions. The analysed time window for the FRN (250–330 ms) is highlighted in grey. Topoplot shows the scalp distribution of the difference between the conditions averaged across the FRN time window.

Fig. 4

The model shows different ways in which the presence of others may influence outcome monitoring and sense of agency. The pathways in black show mechanisms which can explain findings of previous studies, but are, as we show in this study, not necessary for diffusion of responsibility to occur. The central pathway (in red) shows the mechanism we propose, which can explain the observed effects in the absence of ambiguity and post-hoc justification.