Humans may have behavioral adaptations that serve as an early defense against infectious pathogens, helping them to avoid exposure to sickness. While adults detect and avoid cues of sickness in faces, less is known about how these abilities develop in children. This understanding is important because children may be particularly vulnerable to catching and spreading contagious diseases. To better understand the development of this sensitivity to sick faces, we tested whether 4- to 5-year-olds (N = 57), 8- to 9-year-olds (N = 52), and adults (N = 51) can discriminate between sick and healthy faces. We found that, while 4- to 5-year-olds did not identify sick faces at rates above chance, both 8- to 9-year-olds and adults did. When asked who they would rather sit next to at dinner, only adults avoided sick faces at rates above chance. For all age groups, performance was better when asked to identify sickness compared to when asked which person they would avoid, suggesting recognition skills may develop before avoidance and that providing viewers with information about a person potentially having an illness may prime them for disease detection. In sum, the ability to distinguish sick from healthy faces emerged during childhood (between 4 to 9 years of age) but improved with age. Characterizing the development of sensitivity to sickness cues may help determine how to facilitate pathogen avoidance behaviors to reduce the spread of illness and ultimately improve child and family health.
