Asp et al. Neural correlates of credulity Participants’ responses were measured on a Likert scale, anchored by “Likely” and “Unlikely.” This scale ranged from 1 to 5, with 1 reﬂecting a higher intention to purchase the item and 5 reﬂecting a lower intention to purchase the item. NEUROANATOMICAL ANALYSIS The neuroanatomical analysis of the vmPFC and BDC patients (Figures 1 and 2) was based on magnetic resonance data for 30 patients and on computerized tomography data for 9 patients. Using Brainvox (Frank et al., 1997), each patient’s lesion was recon- structed in three dimensions for the different groups. The lesion contour for each patient was manually warped into a normal tem- plate brain using the MAP-3 method. The overlap of lesions in these volumes, calculated by the sum of n lesions overlapping at any single voxel, is color-coded in Figures 1 and 2. As Figure 1 shows, the greatest overlap of vmPFC patient lesions is in the mesial orbital region, especially the anterior half of the gyrus rectus. The greatest overlap of lesions in Figure 2 is in the infe- rior temporal lobes. No BDC lesions encompassed the prefrontal cortex. RESULTS All statistical t -tests are one-tailed in accordance with our directional predictions. CREDULITY DIMENSION The ﬁrst question we addressed was whether patients with vmPFC damage were more likely to be credulous to the mislead- ing advertising overall (including both “deception-uncorrected” and “deception-corrected”). VMPFC patients were more credu- lous to the misleading advertising (M D 3.89, SD D 1.11) than BDC patients (M D 5.25, SD D 0.81) and normal participants (M D 5.10, SD D 0.88; Figure 3). Because BDC patients were slightly younger and had more females relative to males (Table 1), we ran an ANCOVA with age and sex as covariates. The covari- ate, age, was not signiﬁcantly related to credulity, F (1,44) D 0.01, p D 0.93; and the covariate, sex, was also not signiﬁcantly related to credulity, F (1,44) D 0.01, p D 0.92. There remained a signiﬁcant difference in group credulity after controlling for the covariates, F (2,44) D 9.26, p < 0.001. Planned contrasts revealed that vmPFC patients were more credulous than BDC patients, t (44) D 3.17, p D 0.002, and normal participants, t (44) D 3.88, p < 0.001. Ventromedial prefrontal cortex patients had signiﬁcantly larger lesions that BDC patients (Table 1) and there was a modest cor- relation between lesion size and credulity to the ads, r D 0.31, p D 0.06. Thus, a secondary analysis was conducted to directly examine the inﬂuence of lesion size on the credulity measure in the two patient groups. The covariate, lesion size, was not signiﬁcantly related to credulity, F (1,36) D 0.12, p D 0.74. There remained a signiﬁcant difference in group credulity after controlling for the covariate, F (1,36) D 13.70, p D 0.001. Splitting the overall credulity results into the three “deception- uncorrected” ads and the three “deception-corrected” ads helps clarify our initial analysis. VMPFC patients were more credu- lous to the “deception-uncorrected” ads (M D 3.24, SD D 1.38) than BDC patients (M D 4.86, SD D 1.03) and normal partici- pants (M D 4.83, SD D 1.47; Figure 3). There was a signiﬁcant FIGURE 3 | Mean belief scores for misleading ads. The scale is from 1 to 7 (y -axis), with lower values corresponding to increased belief in misleading aspects of the ads and higher values corresponding to increased skepticism for misleading aspects of the ads. Error bars indicate SEM. The graph on the left of the black bar represents results for all six misleading ads; the graph on the right of the black bar breaks the results down according to “deception-uncorrected” and “deception-corrected” ads. For all the ads, vmPFC patients had more credulity than BDC patients and normal comparison participants. difference for group credulity on the “deception-uncorrected” ads, F (2,46) D 9.25, p < 0.001. Planned contrasts revealed that vmPFC patients were more credulous than BDC patients, t (46) D 4.18, p < 0.001, and normal participants, t (46) D 3.20, p D 0.002. vmPFC patients were also more credulous to the “deception- corrected” ads (M D 4.54, SD D 1.17) than BDC patients (M D 5.64, SD D 1.13) and normal participants (M D 5.37, SD D 0.85; Figure 2). There was a signiﬁcant difference for group credulity on the “deception-corrected” ads, F (2,46) D 5.06, p D 0.01. Planned contrasts revealed that vmPFC patients were more credulous than BDC patients, t (46) D 2.90, p D 0.003, and normal participants, t (46) D 1.92, p D 0.03. These data suggest that higher credulity toward misleading ads in vmPFC patients was obtained even when explicit disclaimers should induce doubt for the misleading information. A secondary repeated measures ANOVA analysis was con- ducted to see if the “correction” in the ads had a signiﬁcant main effect. While the participants were generally more skeptical for the “deception-corrected” ads, there was not a signiﬁcant main effect of “correction,” F (1,44) D 0.15, p D 0.70. In addition, the groups Frontiers in Neuroscience | Decision Neuroscience July 2012 | Volume 6 | Article 100 | 6