Transcranial stimulation over the ventromedial prefrontal cortex increases money illusion

In this study, we aim to explore the neural mechanisms underlying money illusion.
To do so, we conduct two transcranial direct current stimulation (tDCS) experiments and test the role of the ventromedial prefrontal cortex (vmPFC) in money illusion.
In tDCS Experiment 1, participants were asked to perform an evaluative task, adapted from Weber et al. (2009), in which they could earn income by counting points and then spend their income purchasing goods displayed in a catalog. Experiment 1 consisted of two price conditions. In the high-price condition, the income and catalog prices were 500% higher than those in the low-price condition. Therefore, the nominal value was different, but the real purchasing power of income was identical in the two conditions. We also collected the participants’ self-reported level of happiness. Money illusion was measured by the difference in the self-reported level of happiness between the high- and low-price conditions when participants made correct choices.
In tDCS Experiment 2, an incentivized task, adapted from Darriet et al. (2020), was used to measure money illusion at the individual level in the context of financial choices. The task consisted of 40 trials, varied by four characteristics of financial choices on money illusion: price changes, real and nominal values, initial values, and differences in final real values. In each trial, participants were to select one of two areas to work on for one trial, one with a higher real value and the other with a lower real value. The two areas differed in terms of wage and inflation rate. In each trial, there was a correct answer, namely, choosing the area with the higher real value. Otherwise, participants made an error and exhibited money illusion.
While the participants performed the experimental tasks, we applied anodal, cathodal, or sham stimulation over the vmPFC.
The experiment was conducted in Shandong University. All the participants were right-handed and had no prior knowledge of the experiment. They were required to provide written informed consent before the experiment, which was approved by the Ethics Committee of Shandong University.