Logarithm of total stellar mass ℳ_⋆, T (M_⊙) vs. radial age gradient within the bulge radius R_B in Gyr/R_B, as obtained from mass- and light-weighted stellar age determinations (∇(t_⋆, B)_ℳ and ∇(t_⋆, B)_ℒ; upper and lower panel, respectively). Symbols are color-coded according to the bulge classification scheme by BP18 (blue, green and red for iA, iB and iC bulges, respectively). Semi-transparent and solid markers correspond, respectively, to determinations from non-weighted and weighted linear fits. Bulges classified by BP18 as LINER (+) and Seyfert (x) are indicated. Dashed-dotted lines show non-weighted linear fits to weighted ∇(t_⋆, B)_ℳ and ∇(t_⋆, B)_ℒ determinations, the arithmetic average of which for the three bulge classes is depicted by stars.