Supplementary Figure 8: Comparison of honesty effect under real versus hypothetical payoffs.
From: Damage to dorsolateral prefrontal cortex affects tradeoffs between honesty and self-interest
To compare honesty effect under hypothetical and real payment, the latter being more common in previous studies on signaling game experiments, we collected additional data of 14 participants on 3 sets of outcomes identical to Gneezy2 using real payoffs. First, we adopted the analysis in Gneezy2, comparing proportions of selfish choices based on the same sets of outcomes across Gneezy2, study with real payoffs and the study with hypothetical payoffs. The proportions of selfish decisions are quite similar across 3 datasets (Choice condition: 66%±4% (Gneezy 2005) vs. 74%±12% (real payoffs) vs. 70%±8.82% (hypothetical payoffs), Message condition: 35%±4.27% vs. 34%±12.66% vs. 21%±7.84% (Chi-square test, p>.30 for both comparisons, two-tailed). In addition, following the analysis in the present study, we compared paired difference of amount given between the Message and Choice condition with and without real payment. We found a small reduction in the honesty effect under real payoffs (2.76±.37 vs. 3.38±.62, with and without real payoffs respectively), but these were not significant (two-sample t-test, p>0.10, two-tailed). Note that we did not include Gneezy2 in this comparison, as paired differences are not possible due to its between-subject design.
