When making a decision, individuals have their own preferences and thresholds for what constitutes a ‘risky’ or ‘safe’ choice. These thresholds, however, can change when people are in social situations and know what choices others have made. While the impact of this knowledge on decision making is known, the neural mechanism for how people integrate and use the decisions of others to modify their choices of safe or risky options is not established.
Decisions made alone tend to be guided by both the subjective preference of the decider and more objective factors such as certainty of outcome and expected value. Additionally, solo decisions tend to be more risk-averse. However, an individual’s probability of choosing a risky or safe option may be modified by information about what others have chosen in the same situation. In a recent study, Chung et al. used fMRI and a clever decision-making task to tease apart the impact the choices of others play on individual decisions and to identify the possible neural correlates of how the choices of others are integrated with one’s personal choice preferences.
In the experiment, participants were asked to make a series of gambles which carried high or low payouts. Each had equal outcome probabilities, but different variance such that one option was ‘safer’ if the variance was lower. On some trials, the participant would place their gamble on their own (solo), while on others, they would know—prior to making their own choice—what two other participants selected. The researchers then developed the ‘other-conferred utility’ (OCU) model to explain how information about other participants’ decisions changed the decider’s subjective value (or utility) of the gamble.
In cases where participants had information about the decisions of others, neural activity in the ventral medial prefrontal cortex (vmPFC) covaried with the OCU, but not with the solo subjective utility of the participants placing the gamble. Amazingly, the strength of vmPFC activation correlated with the degree that a participant’s choice was influenced by the choices of other participants. Additionally, neural regions associated with conflict and risk (the anterior cingulate cortex (ACC) and insula) were activated not by OCU, but whenever the choices of others were incompatible with the solo preferences of the participant. Put simply, ACC and insula activation was high when the decisions of others opposed the subjective preference of the participant, while the vmPFC was active when participants used the decisions of others to influence their own risky choices.
This study verifies a role for the ACC and insula in signaling high conflict situations and identifies a novel role for how the vmPFC may be critical in mediating the integration of social information into personal subjective choice. Further, this research developed a model to explain that the shift in personal risky choices related to a change in the subjective utility of a choice. Such information may be of high importance when understanding how social pressure affects decision making.
- Chung D, Christopoulos GI, King-Casas B, Ball SB, Chiu PH (2015) Social signals of safety and risk confer utility and have asymmetric effects on observers' choices. Nature Neuroscience 18, 912-916. doi: 10.1038/nn.4022