According to the World Health Organization, infectious disease is a leading cause of death among children. Additionally, children are more likely than adults to contract infectious illnesses. However, there's a gap in research measuring children's responses to sick faces.
Previous research has reported that adults can use faces to recognize if someone is sick and make judgments about whether to approach or avoid them. Yet, it's important to understand how children's ability to recognize and avoid sickness emerges and develops to help improve children's health—and public health—more broadly.
To address this question, researchers from the University of Miami, Chinese University of Hong Kong Shenzhen, Duke University, and James Madison University collected photos of people's faces when they were sick with a short-term, contagious illness, such as COVID-19, and when they were feeling healthy.
The collaborative study is among the first to use face photos from individuals experiencing natural symptoms of illness and the same individuals when they are healthy. The findings, published in the journal Child Development, showed that adults and older children (ages 8 and 9) were able to avoid and recognize sick faces.
"Building upon our previous studies in adults, we hypothesized that sensitivity to facial cues of sickness would emerge in childhood (ages 4 to 9). We predicted that this sensitivity would increase with age, reflecting a behavioral immune system that becomes fine-tuned through experience," said Tiffany Leung, a developmental psychology doctoral student at the University of Miami, who led these projects. "By better understanding how people naturally avoid illness in others, we may identify what information is used and ultimately improve public health."
The study sample included 160 participants, both children and adults, and was conducted entirely online via Zoom. Participants were presented with two faces—one sick and one healthy—from the same person, side by side. They were then asked to choose among faces with the question ("Which twin would you rather sit next to at dinner?") to assess their preference for approaching healthier people. Participants were also asked to identify which person was feeling sick, which enabled researchers to capture participants' explicit recognition of sickness.
The study found that children (ages 8 and 9) can avoid and recognize sick faces. In addition, adults were more accurate at avoiding and recognizing sick faces than the 8- to 9-year-olds, who were more accurate than 4- to 5-year-olds, suggesting that these skills improve with age. Children who were more accurate at recognizing sick faces were also more accurate at avoiding them. The findings add to a growing body of knowledge that humans are sensitive to illness in faces.
"We're so grateful to everyone who took part in our studies and especially to those who donated photos of their faces when they were sick," said Elizabeth Simpson, associate professor of psychology and Director of the Developmental Psychology Program at the University of Miami in the College of Arts and Sciences. "To explore whether we can improve sick face perception skills and improve public health, we are continuing to collect sick face photos from adults and children."
