Prestige bias and incentives: Testing two theories in an advice-giving scenario among Maasai pastoralists

Cultural evolutionary researchers have theorized about how and why people use social information to guide decision-making. Some have suggested that for humans, decisions based on social information are primarily guided by cognitive biases using contextual cues to inform simple decision rules. On this view, the presentation of a special type of cue in social context triggers a corresponding cognitive mechanism systematically biasing the decision-maker. Proponents of this view describe social learning biases, e.g., prestige and conformity biases, as "simple heuristics that make us smart" (sensu Gigerenzer and Todd 1999). Importantly, they are efficient by virtue of the restricted range of social cues that they process. Prestige bias, for example, was hypothesized by Henrich and Gil-White (2001) as a context-relevant bias, and relies on a "[preference for] information from models to whom other learners have preferentially attended or deferred" (Chudek et al. 2012, p. 47). We refer to this idea that humans take advice with a systematic decision-making bias favoring prestige as the prestige bias model (PM). Others suggest that such decisions are primarily guided by sensitivity to incentive structure in the decision-making task. Proponents of this view emphasize the role of self-interested reasoning, particularly about material incentives, in decision-making and belief formation. When decision tasks are inherently uncertain or involve risk, inferences guided by expected incentives imply that decisions will be sensitive to risk attitudes and/or payoff structure. This is also highly compatible with a weaker interpretation of the role of social information in human decision-making: on this view, social cues might (or might not) include prestige as one of a wide range of ecologically rational cues that a decision-maker can flexibly combine with personal knowledge (e.g., Morin 2016, ch. 3). In sum, more ambiguous cues might be overruled by more reliable cues and/or incentives, and the range of social cues available to a decision-maker is not necessarily restricted a priori in a specific way. We refer to this approach to evaluating advice with a focus on self-interest and incentives as the rational incentives model (IM). We test these two perspectives in a simple vignette experiment. Specifically, we described a high-cost/high-benefit advice-giving scenario among Maasai pastoralists about where and why they could move their herds. We manipulated the source of this advice in two separate conditions, measuring the perceived trustworthiness of advice in the vignette. Maasai in this population often rely to varying degrees on livestock for subsistence, and must carefully plan their herd movements to avoid wasting energy in a challenging region with scarce grass and water available. It is therefore worth emphasizing that the advice given in this (hypothetical) vignette describes certain costs and possible benefits to their cattle.