Modulating tDCS effects through expectations and reward

Abstract

Previous studies regarding sham tDCS have indicated that expectation priming (Rabipour et al, 2018; Turi et al, 2016), and also reward promise have been able to modulate sham tDCS (Jones et al. 2015). The current study aimed to investigate how expectation priming and reward promise affected reaction times and accuracy on a flanker task during sham tDCS. Participants were divided into four groups, receiving either positive or neutral expectation priming, and either a reward promise or no reward promise. A two-factor ANOVA was used to analyse the data. Results indicated no effects of expectation priming nor reward promise on reaction times. Results did indicate that participants who were positively primed made less errors compared to neutrally primed participants. Similarly, participants receiving the extra reward instruction made less errors compared to participants in the no reward condition. The current study findings suggest that expectation priming, and reward promise are able to modulate sham tDCS effects. One important note is that the current study only included sham tDCS, therefore conclusions comparing active and sham tDCS cannot be made. We discussed our current findings and how these relate to previous studies. Recommendations were made for future research regarding investigating the effects of expectation priming and reward in sham tDCS.