Do infants use cues of saliva-sharing to infer close relationships? A replication of Thomas et al. (2022)

Thomas and colleagues found in 2022 that the observation of saliva-sharing between individuals serves as an indicator of relationship thickness for children, toddlers and infants. Our study sought to replicate their crucial experiment (2B), which was conducted online and reported that 8.5- to 10-month-old infants anticipated that a crying individual would be more likely to be comforted by a person who had been observed to share saliva with her than another person who simply had played with her. With the exception of changing the testing environment from online to laboratory, and using an eye-tracker supplemented by manual video coding, we closely followed the methodology of the original study. Our replication resulted in partial success: we replicated looking-time preference for the saliva-sharer but did not replicate the tendency to look first to the saliva-sharer upon observing the puppet’s distress. These findings confirm that infants rely on certain behavioural cues for mapping social relationships among third-party individuals.