An associative learning account of how saliva becomes a cue for comfort

A recent study by Thomas et al. (2022) showed that 8.5- to 10-month-olds use saliva sharing as an indicator of relationship closeness: infants expect that someone who previously shared saliva with a partner will also comfort that partner during times of distress. The current paper offers a mechanistic explanation for this finding. We propose that through everyday experiences, saliva sharing and comforting become integrated into an enriched representation that contains information about both events. Across five simulations, we show that when this proposal is implemented in a connectionist computational model, the model reproduces infants' looking behaviors in the study by Thomas et al. (2022) (Simulation 1), captures the finding that infants' responses were specific to comfort (Simulation 2), predicts bidirectional expectations about saliva sharing and comforting (Simulation 3), and shows that these expectations strengthen with experience and can shift in response to changes in environmental statistics (Simulations 4 and 5). Taken together, our findings suggest that domain-general associative learning can explain how infants come to understand the social meaning of saliva sharing.