Private but not social information validity modulates social conformity bias.

It is well established that human behaviors are susceptible to others' opinions. However, optimal decision theory mandates choices be made upon the estimated validities of different information sources and little is known about whether and how people could wean themselves off social conformity bias, especially when the social signals are uninformative. Here, we asked subjects to participate in a probabilistic urn guessing task based on their private information as well as observed choices from their partners. Specifically, we manipulated the information validity of these two sources such that only the private evidence was informative. Across trials, social conformity declined, manifested by the increased influence of the private evidence but steady effect of social information. Correspondingly, we found dorsomedial prefrontal cortex (dmPFC) was involved in detecting the conflict of private and social information and conforming to social signal whereas striatum was responsible for selectively updating the influence of private (but not social) evidence contingent on its inferred validity. Furthermore, functional coupling between striatum and dmPFC predicted the resistance toward the influence of social information. Together, these results may provide a mechanistic account of how the conformity bias toward uninformative social information can be remedied.

Source preference and ambiguity aversion: models and evidence from behavioral and neuroimaging experiments.

PURPOSE: This experimental economics study using brain imaging techniques investigates the risk-ambiguity distinction in relation to the source preference hypothesis (Fox & Tversky, 1995) in which identically distributed risks arising from different sources of uncertainty may engender distinct preferences for the same decision maker, contrary to classical economic thinking. The use of brain imaging enables sharper testing of the implications of different models of decision-making including Chew and Sagi's (2008) axiomatization of source preference. METHODOLOGY/APPROACH: Using fMRI, brain activations were observed when subjects make 48 sequential binary choices among even-chance lotteries based on whether the trailing digits of a number of stock prices at market closing would be odd or even. Subsequently, subjects rate familiarity of the stock symbols. FINDINGS: When contrasting brain activation from more familiar sources with those from less familiar ones, regions appearing to be more active include the putamen, medial frontal cortex, and superior temporal gyrus. ROI analysis showed that the activation patterns in the familiar-unfamiliar and unfamiliar-familiar contrasts are similar to those in the risk-ambiguity and ambiguity-risk contrasts reported by Hsu et al. (2005). This supports the conjecture that the risk-ambiguity distinction can be subsumed by the source preference hypothesis. RESEARCH LIMITATIONS/IMPLICATIONS: Our odd-even design has the advantage of inducing the same "unambiguous" probability of half for each subject in each binary comparison. Our finding supports the implications of the Chew-Sagi model and rejects models based on global probabilistic sophistication, including rank-dependent models derived from non-additive probabilities, e.g., Choquet expected utility and cumulative prospect theory, as well as those based on multiple priors, e.g., alpha-maxmin. The finding in Hsu et al. (2005) that orbitofrontal cortex lesion patients display neither ambiguity aversion nor risk aversion offers further support to the Chew-Sagi model. Our finding also supports the Levy et al. (2007) contention of a single valuation system encompassing risk and ambiguity aversion. ORIGINALITY/VALUE OF CHAPTER: This is the first neuroimaging study of the source preference hypothesis using a design which can discriminate among decision models ranging from risk-based ones to those relying on multiple priors.