<p>Timing of age-related differences in intrinsic timescale across two developmental cohorts.</p>

Specifically, the age of peak change was estimated as the age where the derivative was greatest in absolute magnitude. <b>(b)</b> To estimate the age at which age-related timescale differences were maximally aligned with the S–A axis, we calculated the first derivative of each region’s GAM smooth function for age.

These derivatives represent the estimated rate of timescale differences per one-year age interval. At each age, we quantified the spatial correlation between regional derivative values and regional S–A axis ranks. To account for uncertainty in derivative estimates, we sampled 10,000 draws from the posterior derivative distribution and calculated the derivative-to-SA axis correlation for each draw.