Social information use (i.e., learning from information obtained by observing or interacting with others) is essential for human adaptation, skill acquisition, and cultural evolution. Despite its importance, we lack a comprehensive understanding of how social information use develops across the full human lifespan and in diverse cultures. We conducted a preregistered, cross-sectional study with over 32,000 participants aged 6–99 in Berlin (Germany) and Tokyo (Japan), using the BEAST (Berlin Estimation Adjustment Task) with manipulations of key situational factors (distance, agreement, source age). 

Results showed that social information use followed a clear developmental trajectory: high in early childhood, declining through adolescence, and stabilising in adulthood, with age explaining the most variance compared to other factors. While the overall developmental pattern was highly consistent across groups, we also observed differences in levels of social information use: it was slightly higher in females than males, and higher in German than Japanese participants. In conclusion, we argue that age is a major driver of social information use, likely reflecting adaptive life-stage needs.