Identification of acutely sick people and facial cues of sickness.

Detection and avoidance of sick individuals have been proposed as essential components in a behavioural defence against disease, limiting the risk of contamination. However, almost no knowledge exists on whether humans can detect sick individuals, and if so by what cues. Here, we demonstrate that untrained people can identify sick individuals above chance level by looking at facial photos taken 2 h after injection with a bacterial stimulus inducing an immune response (2.0 ng kg-1 lipopolysaccharide) or placebo, the global sensitivity index being d' = 0.405. Signal detection analysis (receiver operating characteristic curve area) showed an area of 0.62 (95% confidence intervals 0.60-0.63). Acutely sick people were rated by naive observers as having paler lips and skin, a more swollen face, droopier corners of the mouth, more hanging eyelids, redder eyes, and less glossy and patchy skin, as well as appearing more tired. Our findings suggest that facial cues associated with the skin, mouth and eyes can aid in the detection of acutely sick and potentially contagious people.

Multisensory flavor perception: The relationship between congruency, pleasantness, and odor referral to the mouth.

Our hedonic response to a food is determined by its flavor, an inherently multisensory experience that extends beyond the mere addition of its odor and taste. While congruency is known to be important for multisensory processes in general, little is known about its specific role in flavor processing. The aim of the present study was to delineate the effects of odor-taste congruency on two central aspects of flavor: odor referral (or mislocalization) to the mouth, and pleasantness. We further aimed to test whether an eventual effect on pleasantness was mediated by odor referral. Aqueous solutions containing odors and tastes were prepared to create food-like stimuli with varying degrees of congruency, ranging from maximally incongruent to maximally congruent in nine steps. Thirty participants reported where they perceived the odors, and how much they liked the solutions. Congruency had a positive linear effect both on odor referral to the oral cavity and on pleasantness. However, the effect of congruency on pleasantness was not mediated by odor referral. These results indicate that as an odor-taste mixture approximates a mental representation of a familiar food, its components are increasingly merged into one perceptual object sensed in the mouth. In parallel, the mixture is evaluated as increasingly pleasant, which promotes consumption of familiar foods that have been determined through experience to be non-toxic. While the modulatory role of congruency on pleasantness and odor referral was confirmed, our results also indicate that these effects arise through distinct perceptual mechanisms.