A study of almost 38,000 adults finds that the more kids they had, the more synchronized the activity between certain brain regions became. The strongest association between the number of children and functional connectivity turned up in a brain network believed to aid in inferring others’ thoughts, researchers report in the March 4 Proceedings of the National Academy of Sciences. Coordinated activity within this network typically decreases with age, suggesting that child-rearing — which involves learning new skills — may provide long-lasting protection against brain aging