Triadic interactions support infants' emerging understanding of intentional actions

Abstract

Infants' understanding of the intentional nature of human action develops gradually across the first year of life. A key question is what mechanisms drive changes in this foundational social-cognitive ability. The current studies explored the hypothesis that triadic interactions in which infants coordinate attention between a social partner and an object of mutual interest promote infants' developing understanding of others as intentional agents. Infants' spontaneous tendency to participate in triadic engagement was assessed in a semi-structured play session with a researcher. Intentional action understanding was assessed by evaluating infants' ability to visually predict the goal of an intentional reaching action. Study 1 (N = 88) revealed that 8- to 9-month-olds who displayed more bouts of triadic engagement showed better concurrent reasoning about the goal of an intentional reaching action. Study 2 (N = 114) confirmed these findings using a longitudinal design and demonstrated that infants who displayed more bouts of triadic engagement at 6-7 months were better at prospectively reasoning about the goal of an intentional reaching action 3 months later. Cross-lagged path analyses revealed that intentional action understanding at 6-7 months did not predict later triadic engagement, suggesting that early triadic engagement supports later intentional action processing and not the other way around. Finally, evidence from both studies revealed the unique contribution of triadic over dyadic forms of engagement. These results highlight the importance of social interaction as a developmental mechanism and suggest that infants enrich their understanding of intentionality through triadic interactions with social partners.

Keywords: cognitive development; infancy; intention understanding; joint engagement; social cognition; triadic interaction.

Figure 1.

Time course depiction of the (a) failed (Study 1 & 2) and (b) successful (Study 2) reaching events.

Figure 2.

Estimated mean likelihood of producing an anticipatory look to the ball AOI (± standard error) in the failed and successful reaching events as a function of trial (1 to 5) and time point (Time 1 vs. Time 2) in Study 2.

Figure 3.

Cross-lagged path models of triadic engagement and intentional action understanding in Study 2. The first model (a) uses the proportion of anticipatory looks to the ball AOI in the failed and successful reaching events as the measure of intentional action understanding. The second model (b) uses the mean latency of looking to the ball AOI across the failed and successful reaching events. **p < .01, *p < .05. Path coefficients are standardized.