Let's get it together: Infants generate visual predictions based on collaborative goals

Encoding interactive scripts at 10 months of age

Understanding action-reaction associations that give origin to interactive scripts (e.g., give-and-take interactions) is essential for appreciating social exchanges. However, studies on infants' action understanding have mainly investigated the case of actions performed by individual agents. Moreover, although extensive literature has explored infants' comprehension of action-effect relationships in object functioning, no study has addressed whether it also plays a role when observing social interactions, an issue we addressed here. In a first study, 10-month-old infants observed short videos of dyadic exchanges. We investigated whether they were able to link specific human gestures directed toward another person to specific vocal reactions in the receiver. We used a double-habituation paradigm in which infants were sequentially habituated to two specific action-reaction associations. In the test phase, infants watched one of the two habituated (Familiar) videos, a video with a reversed action-reaction association (Violation), and a Novel video. Results showed that the infants looked longer at both the Novel and Violation test trials than at the Familiar test trials. In a control study, we show that these results could not be accounted for by associative learning; indeed, learning of the action-reaction association did not occur when the vocalization was not produced by the receiver but only contingent on the agent's action. Thus, we show that 10-month-old infants can encode specific social action-effect relationships during the observation of dyadic interactions and that the interactivity of the social context may be critical to shaping young infants' understanding of others' behaviors.

Infants expect agents to minimize the collective cost of collaborative actions

This paper argues that human infants address the challenges of optimizing, recognizing, and interpreting collaborative behaviors by assessing their collective efficiency. This hypothesis was tested by using a looking-time study. Fourteen-month-olds (N = 32) were familiarized with agents performing a collaborative action in computer animations. During the test phase, the looking times were measured while the agents acted with various efficiency parameters. In the critical condition, the agents' actions were individually efficient, but their combination was either collectively efficient or inefficient. Infants looked longer at test events that violated expectations of collective efficiency (p = .006, d = 0.79). Thus, preverbal infants apply expectations of collective efficiency to actions involving multiple agents.

Neural correlates of familiar and unfamiliar action in infancy

Behavioral evidence shows that experience with an action shapes action perception. Neural mirroring has been suggested as a mechanism underlying this behavioral phenomenon. Suppression of electroencephalogram (EEG) power in the mu frequency band, an index of motor activation, typically reflects neural mirroring. However, contradictory findings exist regarding the association between mu suppression and motor familiarity in infant EEG studies. In this study, we investigated the neural underpinnings reflecting the role of familiarity in action perception. We measured neural processing of familiar (grasp) and novel (tool-use) actions in 9- and 12-month-old infants. Specifically, we measured infants' distinct motor/visual activity and explored functional connectivity associated with these processes. Mu suppression was stronger for grasping than for tool use, whereas significant mu and occipital alpha (indexing visual activity) suppression were evident for both actions. Interestingly, selective motor-visual functional connectivity was found during observation of familiar action, a pattern not observed for novel action. Thus, the neural correlates of perception of familiar actions may be best understood in terms of a functional neural network rather than isolated regional activity. Our findings provide novel insights on analytic approaches for identifying motor-specific neural activity while also considering neural networks involved in observing motorically familiar versus unfamiliar actions.

Taking apart what brings us together: The role of action prediction, perspective-taking, and theory of mind in joint action

The ability to act together with others to achieve common goals is crucial in life, yet there is no full consensus on the underlying cognitive skills. While influential theoretical accounts suggest that interaction requires sophisticated insights into others' minds, alternative views propose that high-level social skills might not be necessary because interactions are grounded on sensorimotor predictive mechanisms. At present, empirical evidence is insufficient to decide between the two. This study addressed this issue and explored the association between performance at joint action tasks and cognitive abilities in three domains-action prediction, perspective-taking, and theory of mind-in healthy adults (N = 58). We found that, while perspective-taking played a role in reading the behaviour of others independently of the social context, action prediction abilities specifically influenced the agents' performance in an interactive task but not in a control (social but non-interactive) task. In our study, performance at a theory of mind test did not play any role, as confirmed by Bayesian analyses. The results suggest that, in adults, sensorimotor predictive mechanisms might play a significant and specific role in supporting interpersonal coordination during motor interactions. We discuss the implications of our findings for the contrasting theoretical views described earlier and propose a way they might be partly reconciled.