We animals have evolved a variety of mechanisms to avoid conspecifics who might be infected. It is currently unclear whether and why this “behavioral immune system” targets unfamiliar individuals more than familiar ones. Here I answer this question in humans, using publicly available data of a recent study on 1969 participants from India and 1615 from the USA. The apparent health of a male stranger, as estimated from his face, and the comfort with contact with him were a direct function (...) of his similarity to the men in the local community. This held true regardless of whether the face carried overt signs of infection. I conclude that our behavioral immune system is finely tuned to degrees of outgroupness — and that cues of outgroupness are partly processed as cues of infectiousness. These findings, which were consistent across the two cultures, support the notion that the pathogens of strangers are perceived as more dangerous. (shrink)

Von Hippel & Trivers (VH&T) interpret belief in God and belief in strong government as the outcome of an active process of self-deception on a worldwide scale. We propose, instead, that these beliefs might simply be a passive spin-off of efficient cognitive processes.

Human beings are among the species with the best color perception of all mammals. Yet, transparency can be perceived in scenes in which color cues point to opacity. Why do we ignore such color cues? Here we argue that colors, rather than being passively registered, must be actively recreated and then bound to other stimulus attributes. In this process, the visual system faces fundamental problems, some of which are logically impossible to solve. The resulting unreliability of color perception may go (...) some way toward explaining why color cues cannot usually veto transparency percepts. Other stimulus attributes, however, affect transparency perception strongly even though they are not processed in foolproof ways either. How come? We argue that our trichromatic color perception is likely to have been a late, and for that reason less than fully integrated, addition to an already existing visual system that was colorblind to red and green. (shrink)