Peer presence elicits task-independent changes within and beyond the mentalizing network across children and adults

There is ample behavioral evidence that others’ mere presence can affect any behavior in human and non-human animals, generally facilitating the expression of mastered responses while impairing the acquisition of novel ones. Much less is known about i) how the brain orchestrates the modulation of such a wide array of behaviors by others’ presence and ii) when these neural underpinnings mature during development. To address these issues, fMRI data were collected in children and adults alternately observed and unobserved by a familiar peer. Subjects performed two tasks. One, numerosity comparison, depends on number-processing brain areas, the other, phonological comparison, on language-processing areas. Consistently with previous behavioral findings, peer observation facilitated both tasks, and children’s improvement was comparable to adults’. Regarding brain activation, we found virtually no evidence of observation-driven changes within the number- or language-related areas specific to each task. Rather, we observed the same task-independent changes for both numerosity and phonological comparisons. This unique neural signature encompassed a large brain network of domain-general areas involved in social cognition, especially mentalizing, attention, and reward. It was also largely shared by children and adults. The one exception was children’s right temporoparietal junction, which failed to show the observation- driven lesser deactivation seen in adults. These findings indicate that social facilitation of some human education-related skills is i) primarily orchestrated by domain-general brain networks, rather than by task-selective substrates, and ii) relatively mature early in the course of education, thus having a protracted impact on academic achievements that may have heretofore been underestimated. Highlight ### Competing Interest Statement The authors have declared no competing interest.