Quantifying Placebo Using tDCS and Subject Expectancy
The placebo effect is a psychobiological phenomenon (Petrie & Rief, 2019) that has long been studied, especially in placebo-prone experimental designs, such as transcranial direct current stimulation (tDCS). To date, it is rarely quantified and is usually only done so in clinical trials for new therapeutic methods (Owens & Menard, 2011). We sought to quantify the placebo effect using bilateral transcranial direct current stimulation (tDCS) (anodal, cathodal, and sham stimulation) of the dorsolateral prefrontal cortex (DLPFC) paired with verbal expectancy cues. We will also be studying if and how the placebo effect interacts with metacognitive sensitivity, the efficacy with which confidence ratings discriminate between correct and incorrect answers. In addition to this, we also studied whether stimulation of DLPFC affected metacognitive sensitivity to contribute to an ongoing debate on the subject. Subjects were told they would do better, worse, or experience no change in performance during a 2AFC perception task. Pilot data have been collected for various portions of the project.