Detection of sickness in conspecifics using olfactory and visual cues

Abstract

Social communication in humans, although largely based on sophisticated language skills, is also substantially mediated by nonverbal cues that the receiver perceives through his/her senses. It is largely acknowledged that humans are highly visual organisms and that their perception of the social and physical environment is dominated by vision. In the field of person perception (i.e., how we process information about people), an enormous research effort has been dedicated in particular to the understanding of face perception (1) and how information, such as the individual’s emotional state or quality as a mate, can be conveyed through facial features (color, shape, expression, etc.). However, other sensory channels have more recently been revealed as highly pertinent: the auditory channel [through the voice (2)] and the olfactory channel. Although olfaction has long been a neglected sense in humans (3), there is now convincing evidence that humans are efficient in using it (4) and able to extract relevant cues conveyed by smells, and respond to them in an adaptive manner. For example, several experiments using “fear sweat” (body odor produced by donors experiencing fear) revealed emotional contagion in the receiver (5). Alarm is one of the major functions of olfaction (6), with obvious survival relevance. In the food domain, olfactory cues allow us to avoid the deadly threat of ingesting spoiled food. In the social context, threat detection through smell can, for example, materialize in the recognition of infected status. The medical community has been using olfactory cues in diagnoses for centuries (7), and dogs have the ability to recognize sick individuals by smell (8, 9). However, the mechanisms of disease avoidance through smell in humans remain at present poorly explored or understood, in terms of both the nature of the chemicals produced by the healthy or sick individual and the expression and … [↵][1]1To whom correspondence should be addressed. Email: moustafa.bensafi{at}cnrs.fr. [1]: #xref-corresp-1-1