Contagious Crying Revisited: A Cross-Cultural Investigation Into Infant Emotion Contagion Using Infrared Thermal Imaging.

Contagious crying in infants has been considered an early marker of their sensitivity to others' emotions, a form of emotional contagion, and an early basis for empathy. However, it remains unclear whether infant distress in response to peer distress is due to the emotional content of crying or acoustically aversive properties of crying. Additionally, research remains severely biased towards samples from Europe and North America. In this study, we address both aspects by employing the novel and non-invasive method of infrared thermal imaging, in combination with behavioural markers of emotional contagion, to measure emotional arousal during a contagious crying paradigm in a cross-cultural sample of 10- to 11-month-old infants from rural and urban Uganda and the United Kingdom (N = 313). Infants heard social stimuli of positive, negative, and neutral emotional valence (infant laughing, crying, and babbling, respectively) and a non-social, acoustically matched artificial aversive sound. Results revealed that overall changes (as opposed to positive or negative) in infant nasal temperature were larger in response to crying and laughing compared to the artificial aversive sound and larger for crying than for babbling. Infants showed stronger behavioural responses for crying than for the artificial stimulus, as well as for crying than for laughing. Overall, our results support the view that infants within the first year of life experience emotional contagion in response to peer distress, an effect that is not just explained by the aversive nature of the stimuli. Sensitivity to others' emotional signals in the first year of life may provide the core building blocks for empathy.