Abstract
Individuals differ profoundly when they decide whether to tell the truth or to be dishonest, particularly in situations where moral motives clash with economic motives, i.e., when truthfulness comes at a monetary cost. These differences should be expressed in the decision network, particularly in prefrontal cortex. However, the interactions between the core players of the decision network during honesty-related decisions involving trade-offs with economic costs remain poorly understood. To investigate brain connectivity patterns associated with individual differences in responding to economic costs of truthfulness, we used functional magnetic resonance imaging and measured brain activations, while participants made decisions concerning honesty. We found that in participants who valued honesty highly, dorsolateral and dorsomedial parts of prefrontal cortex were more tightly coupled with the inferior frontal cortex when economic costs were high compared to when they were low. Finer-grained analysis revealed that information flow from the inferior frontal cortex to the dorsolateral prefrontal cortex and bidirectional information flow between the inferior frontal cortex and dorsomedial prefrontal cortex was associated with a reduced tendency to trade off honesty for economic benefits. Our findings provide a novel account of the neural circuitry that underlies honest decisions in the face of economic temptations.
Highlights
Individuals differ profoundly when they decide whether to tell the truth or to be dishonest, in situations where moral motives clash with economic motives, i.e., when truthfulness comes at a monetary cost
We found that neural coding of the cost of truthtelling increased with the individual percentage of truthtelling in the dorsolateral prefrontal cortex (DLPFC) and dorsomedial prefrontal cortex (DMPFC) (Fig. 2A,B; DLPFC: −30, 56, 26; t(30) = 4.92; Fig. 2C,D; DMPFC: −6, 16, 44; t(30) = 4.48; both p < 0.05, whole-brain FWE cluster-level corrected; see Supplementary Methods (Control analyses for the identification of the seed regions for the truthtelling psycho-physiological interaction (PPI) analyses) and Supplementary Results (Control analyses: difficulty) for control analyses)
We found that functional connectivity between the DLPFC and the inferior frontal gyrus (IFG) as well as between the DMPFC and the IFG differed significantly as a function of cost-level and honesty-related values (Fig. 3; DLPFC: −46, 28, 30; t(30) = 4.56; DMPFC: −44, 28, 28; t(30) = 5.12; p < 0.05, both whole-brain FWE cluster-level corrected; additional whole-brain cluster-level corrected activation was found in the parietal cortex: −46, −32, 38; t(30) = 4.29)
Summary
Individuals differ profoundly when they decide whether to tell the truth or to be dishonest, in situations where moral motives clash with economic motives, i.e., when truthfulness comes at a monetary cost These differences should be expressed in the decision network, in prefrontal cortex. We hypothesized that connectivity between prefrontal regions should be pronounced in participants with strong honesty-related values when the economic costs of telling the truth are high. This hypothesis has not been investigated so far, even though previous behavioural research clearly showed that individual differences in honesty-related values exist and that economic costs of telling the truth are processed[2,14].
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