Infants are sensitive to the social signaling value of shared inefficient behaviors.

Actions that are blatantly inefficient to achieve non-social goals are often used to convey information about agents' social affiliation, as in the case of rituals. We argue that when reproduced, actions that are individually inefficient acquire a social signaling value owing to the mechanisms that support humans' intuitive analysis of actions. We tested our hypothesis on 15-month-old infants who were familiarized with an agent that reproduced or merely observed the actions of efficient and inefficient individuals. Subsequently, we measured the infants' expectations of the agent's preferences for efficient and inefficient individuals. Our results confirmed that when agents act alone, infants expect a third-party to prefer efficient over inefficient agents. However, this pattern is entirely flipped if the third-party reproduces the agents' actions. In that case, infants expect inefficient agents to be preferred over efficient ones. Thus, reproducing actions whose rational basis is elusive can serve a critical social signaling function, accounting for why such behaviors are pervasive in human groups.

Infants' representation of asymmetric social influence.

In social groups, some individuals have more influence than others, for example, because they are learned from or because they coordinate collective actions. Identifying these influential individuals is crucial to learn about one's social environment. Here, we tested whether infants represent asymmetric social influence among individuals from observing the imitation of movements in the absence of any observable coercion or order. We defined social influence in terms of Granger causality; that is, if A influences B, then past behaviors of A contain information that predicts the behaviors and mental states of B above and beyond the information contained in the past behaviors and mental states of B alone. Infants (12-, 15-, and 18-month-olds) were familiarized with agents (imitators) influenced by the actions of another one (target). During the test, the infants observed either an imitator who was no longer influenced by the target (incongruent test) or the target who was not influenced by an imitator (neutral test). The participants looked significantly longer at the incongruent test than at the neutral test. This result shows that infants represent and generalize individuals' potential to influence others' actions and that they are sensitive to the asymmetric nature of social influence; upon learning that A influences B, they expect that the influence of A over B will remain stronger than the influence of B over A in a novel context. Because of the pervasiveness of social influence in many social interactions and relationships, its representation during infancy is fundamental to understand and predict others' behaviors.

Small groups lead, big groups control: Perceptions of numerical group size, power, and status across development.

Participants (N = 384 three- to ten-year-olds; 51% girls, 49% boys; 73% White, 18% multiracial/other, 5% Asian, and 3% Black; N = 610 adults) saw depictions of 20 individuals split into two social groups (1:19; 2:18; 5:15; or 8:12 per group) and selected which group was "in charge" (Experiment 1), "the leader" (Experiment 2), or likely to "get the stuff" (resources) in a conflict (Experiment 3). Whereas participants across ages predicted the larger group would "get the stuff," a tendency to view smaller groups as "in charge" and "the leader" strengthened with age and when the smaller group was rarer. These findings suggest the perceived relation between numerical group size and hierarchy is flexible and inform theory regarding the developmental trajectories of reasoning about power and status.

Infants' representation of social hierarchies in absence of physical dominance.

Social hierarchies are ubiquitous in all human relations since birth, but little is known about how they emerge during infancy. Previous studies have shown that infants can represent hierarchical relationships when they arise from the physical superiority of one agent over the other, but humans have the capacity to allocate social status in others through cues that not necessary entail agents' physical formidability. Here we investigate infants' capacity to recognize the social status of different agents when there are no observable cues of physical dominance. Our results evidence that a first presentation of the agents' social power when obtaining resources is enough to allow infants predict the outputs of their future. Nevertheless, this capacity arises later (at 18 month-olds but not at 15 month-olds) than showed in previous studies, probably due the increased complexity of the inferences needed to make the predictions.

Efficiency as a principle for social preferences in infancy.

Two separate research lines have shown that (1) infants expect agents to move efficiently toward goal states and that (2) infants navigate the social world selectively, preferring some individuals to others and attributing social preferences to others' agents. Here, we studied how the expectation of efficient actions influences infants' looking preferences and their inferences about others' preferences. We presented 15-month-olds with a set of videos containing three geometric figures depicting social agents. One of them (observer) watched how the other two agents acted to obtain a reward. Critically, the efficiency of their actions was manipulated. One agent reached the reward taking a direct efficient path (efficient agent), whereas the other agent took a curvilinear inefficient path (inefficient agent). At test, the observer approached each of them in two separate trials. Infants looked longer at the screen when the observer approached the inefficient agent rather than the efficient agent. In addition, infants showed a bias to track the actions of the efficient agent when efficient and inefficient agents acted simultaneously. In a second experiment, we rejected the possibility that infants' expectations in Experiment 1 resulted from differences in the movement repertoire of the agents. The results suggest that the principle of efficiency tunes infants' attention towards agents who previously acted efficiently rather than inefficiently and it guides infants' expectations in third-party scenarios-infants are surprised when a third agent approaches an agent who in the past acted inefficiently.

Speak My Language and I Will Remember Your Face Better: An ERP Study.

Here we investigated how the language in which a person addresses us, native or foreign, influences subsequent face recognition. In an old/new paradigm, we explored the behavioral and electrophysiological activity associated with face recognition memory. Participants were first presented with faces accompanied by voices speaking either in their native (NL) or foreign language (FL). Faces were then presented in isolation and participants decided whether the face was presented before (old) or not (new). The results revealed that participants were more accurate at remembering faces previously paired with their native as opposed to their FL. At the event-related potential (ERP) level, we obtained evidence that faces in the NL were differently encoded from those in the FL condition, potentially due to differences in processing demands. During recognition, the frontal old/new effect was present (with a difference in latency) regardless of the language with which a face was associated, while the parietal old/new effect appeared only for faces associated with the native language. These results suggest that the language of our social interactions has an impact on the memory processes underlying the recognition of individuals.