(a) TPJ-OFC connectivity reflecting group-dependent generosity (TPJ seed definition and PPI analysis as described in Fig. 4a). We observed a group difference in TPJ connectivity in a medial OFC region ((18, 38, −17), t(44)=5.60, P<0.05, SV–FWE corrected). Importantly, across participants, this connectivity was modulated by individual generosity (defined by acceptance rate) in a group-dependent manner. (b) In the experimental group, the participants who showed greater TPJ-OFC connectivity during the acceptance of an offer also showed more generous behaviour on average. In the control group, the opposite pattern was observed. Outliers-resistant rank-based correlation analyses confirmed the findings in the experimental group: Kendall’s tie-adjusted tau-b: 0.32, P=0.029, Spearman’s rho: 0.47; P=0.02. (c) We performed an additional analysis with trial-wise changes in subjective value as a parametric regressor. We identified an OFC cluster in which activity reflects the subjective value of the presented option in each trial ((0, 62, −11) t(45)=4.63; P<0.05, SV–FWE corrected). (d) Conjunction analysis confirms that the OFC region tracking subjective value is the very same region being modulated by the TPJ during acceptance decisions (conjuntion of a,c).