Article Figures & Data
Figures
- Figure 1.
Experiment procedure and behavioral results. A, At the beginning of each trial, the participants were (anonymously and ostensibly) paired with 1 of 3 coplayers. Then the participants saw a pain-money pair and waited for the coplayer's decision. If the coplayer chose Help, then the coplayer lost the corresponding amount of bonus while the participants would be exempted from the pain stimulation on this trial. If the coplayer chose NoHelp, then the coplayer could keep the bonus while the participants had to receive the corresponding pain stimulation. The presentation of the coplayer's decision was defined as the critical events in the fMRI data analysis. At the end of the trial, the participant could allocate 20 Yuan (∼$3 U.S.) between himself/herself and the coplayer, with the knowledge that the coplayer was not aware of this procedure. B, C, Postscan gratitude rating and allocation during scanning (i.e., reciprocity) as a function of self-benefit and benefactor-cost. D, Relative weight of benefactor-cost over self-benefit in gratitude rating.
- Figure 2.
Encoding of benefactor-cost. A, Whole-brain contrast of high versus low cost in Help conditions (larger figure). The same contrast in the NoHelp conditions was inserted for comparison (smaller figure). B, Parameter estimates (β values) corresponding to the four Help conditions were extracted from MPFC and rTPJ for illustrative purposes. Error bars indicate standard error of means.
- Figure 3.
Encoding of self-benefit. A, Whole-brain contrast of high versus low benefit in Help conditions (larger figure). The same contrast in the NoHelp conditions was inserted for comparison (smaller figure). B, Parameter estimates (β values) corresponding to the four Help conditions were extracted from left VS and rVS for illustrative purposes. Error bars indicate standard error of means.
- Figure 4.
Representation of gratitude. A, Whole-brain parametric contrast of constructed gratitude. B, pgACC responses to constructed gratitude (blue) and allocation (green). C, Relation between trait gratitude score and pgACC responses to constructed gratitude (blue) and allocation (green). **p < .005. Error bars indicate standard error of means.
- Figure 5.
Results of effective connectivity (DCM) analysis. A, Thirty-three individual models, grouped into 7 model families, were constructed and compared using Bayesian Model Comparison. The exceedance probability of each family (B) and each individual model (C) are shown. Model Family 1, enclosed in the red square, has the highest exceedance probability. D, Strength of intrinsic and modulatory connectivities estimated based on the winning family. *p < 0.05, **p < .005.
- Figure 6.
From gratitude to reciprocity. A, Average gratitude rating in the postscan gratitude recall of an individual participant predicts average monetary allocation (i.e., reciprocity) of that participant. B, Within each individual, variation in gratitude ratings predicts variation in allocation. The correlation reported here is the correlation between the postscan gratitude ratings in each of the 20 Help conditions and the average amount of allocation in the 20 Help conditions. Each dotted line indicates the regression line of a single participant, Solid line indicates the group effect. C, Individual differences in the exchange rate between gratitude and reciprocity (i.e., the slopes of the dotted lines in B). D, Neural correlates of individual differences in the exchange rate. This map is thresholded with p < 0.005 for illustrative purposes.
Tables
No. of NoHelp trials Cost 0 1 2 3 4 Benefit 1 0 3 3 5 5 2 0 3 3 4 5 3 0 2 3 3 3 4 0 1 2 3 3 Model Predictors df −2 ln L BIC ΔBIC w Term Beta SE t 1 Cost 6 2086.0 2124.6 273.6 0.0 Cost 0.83 0.06 13.06 2 Benefit 6 2426.0 2464.5 613.5 0.0 Benefit 0.33 0.11 2.96 3 Cost + benefit 10 1856.4 1920.7 69.7 0.0 Cost 0.83 0.06 13.06 Benefit 0.33 0.11 2.96 4b Cost + benefit 15 1754.5 1851.0 0.0 1.0 Cost 0.80 0.16 5.02 + cost × benefit Benefit 0.30 0.07 4.58 Interaction 0.01 0.05 0.26 Model Predictors df −2 ln L BIC ΔBIC w Term Beta SE t 1 Cost 6 17291.6 17340.0 43.0 0.0 Cost 0.77 0.10 7.96 2 Benefit 6 17390.8 17439.0 142.0 0.0 Benefit 0.62 0.09 7.10 3b Cost + benefit 10 17217.4 17297.0 0.0 1.0 Cost 0.78 0.11 7.43 Benefit 0.64 0.10 6.11 4 Cost + benefit 15 17213.0 17333.0 36.0 0.0 Cost 0.62 0.17 3.63 + cost × benefit Benefit 0.47 0.16 2.98 Interaction 0.07 0.06 1.17 Regions Hemisphere t Cluster size (voxels) MNI coordinates x y z Constructed gratitude pgACC L 3.96 60 −9 44 4 Calcarine R 6.10 275 12 −82 13 Cuneus L 5.48 137 −9 −73 28 Main effect benefit VS R 4.40 30 12 20 −15 L 5.87 117 −18 20 −17 Putamen R 4.19 45 33 11 13 MCC L 4.13 30 −12 −19 43 R 4.01 31 12 −19 43 Temporal pole L 4.09 27 −51 8 −14 Main effect of cost MPFC R 6.25 723 3 47 7 TPJ R 4.70 144 48 −52 31 L 4.84 152 −48 −70 25 PCC/PreCu R 5.00 266 12 −46 34 MTG L 4.39 33 −57 −7 −26 Insula R 5.81 122 33 26 −17 Calcarine R 4.38 47 9 −79 4 Superior frontal gyrus R 4.28 30 21 35 52 ↵aMCC, Middle cingulate cortex; PCC, Posterior cingulate cortex; PreCu, Precuneus; MTG, middle temporal gyrus. Clusters survive p < 0.001 at voxel level and pFWE < 0.05 at cluster level.
Parameter Mean ± SD Intrinsic connectivity VS → pgACC 0.06 ± 0.14* rTPJ → pgACC 0.11 ± 0.18** Modulation on VS → pgACC LowCost_LowBene 0.00 ± 0.06 LowCost_HighBene −0.05 ± 0.42 HighCost_LowBene 0.10 ± 0.30 HighCost_HighBene 0.08 ± 0.67 Modulation on rTPJ → pgACC LowCost_LowBene 0.02 ± 0.06 LowCost_HighBene 0.04 ± 0.39 HighCost_LowBene 0.22 ± 0.59* HighCost_HighBene 0.13 ± 0.60 Driving input to VS Help decision 0.04 ± 0.08* Driving input to TPJ Help decision 0.06 ± 0.15* Condition Connectivity (mean ± SD) LowCost_LowBene 1.51 ± 4.10 LowCost_HighBene 1.17 ± 2.69 HighCost_LowBene 1.44 ± 3.25 HighCost_HighBene 1.83 ± 4.95
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