Evidence against the "anomalous-is-bad" stereotype in Hadza hunter gatherers

Abstract

People have an "anomalous-is-bad" stereotype whereby they make negative inferences about the moral character of people with craniofacial anomalies like scars. This stereotype is hypothesized to be a byproduct of adaptations for avoiding pathogens. However, evidence for the anomalous-is-bad stereotype comes from studies of European and North American populations; the byproduct hypothesis would predict universality of the stereotype. We presented 123 Hadza across ten camps pairs of morphed Hadza faces-each with one face altered to include a scar-and asked who they expected to be more moral and a better forager. Hadza with minimal exposure to other cultures chose at chance for both questions. Hadza with greater exposure to other cultures, however, expected the scarred face to be less moral and a better forager. These results suggest the anomalous-is-bad stereotype may be culturally shared or learned erroneously through associations with population-level differences, providing evidence against a universal pathogen avoidance byproduct hypothesis.

Figure 1

A sample set of composite male faces used in the experiment (face set M1, condition A). The complete set of stimuli are available at https://osf.io/eqftk/.

Figure 2

Joint posterior predictions by participants’ exposure to non-Hadza culture as a z-score and trait being evaluated. Lines are the median estimate from the posterior and shaded regions are the 90% highest density intervals (HDI). Points are individual responses (for plotting, exposure values were rounded to the nearest tenth), with red points at the top indicating when the participant chose the anomalous face, and the yellow points at the bottom indicating when the participant chose the non-anomalous face. Dashed lines indicate the region of practical equivalence (ROPE).

Figure 3

Joint posterior predictions of choosing the anomalous face for good forager judgments by participants’ exposure to non-Hadza culture as a z-score and whether the face was same- or opposite-sex. Lines are the median estimate from the posterior and shaded regions are the 90% highest density intervals (HDI). Points are individual responses (for plotting, exposure values were rounded to the nearest tenth), with red points at the top indicating when the participant chose the anomalous face, and the yellow points at the bottom indicating when the participant chose the non-anomalous face. Dashed lines indicate the region of practical equivalence (ROPE).