Visits 2 - 10 are exclusively treatment visits. At each visit the participant completes the tES Side Effect Questionnaire (TSEQ) both pre and post treatment. Visits occur twice daily for 5 days. Visits must be spaced at least 2 hours apart. Depending on the arm participants have been randomized into, s/he will receive treatment with either tDCS, tRNS, or sham. Treatment will be provided using the Starstim Neurostimulator (Neuroelectrics, Inc.) This device has been approved for use in research in the United States without an investigational device exemption due to meeting criteria for non-significant risk. The same energetic parameters are used for both tDCS and tRNS (2mA for 20 min) as well as the same electrodes (SPONSTIM-25 25cm2 electrodes). Both tDCS and tRNS are initiated in a ramp-like fashion over 10s from 0mA to 2mA. Once at 2mA, tDCS is held constant for the entire session whereas the tRNS consists of an alternating current of 2mA with a 0mA offset applied at random frequencies over a range of 0.1 to 100 Hz. The sham procedure involves only 40 sec stimulation at 2mA and then drops to 0mA with 15msec pulses every 550msec. Should the participant not be able to tolerate a current of 2mA due to pain or irritation, the current will be decreased down to a minimum of 1.5mA. If 1.5 mA is still not tolerable, the participant will be removed from the study. Electrode placement is based on the international 10-20 electrode placement system. The anode is placed at the midpoint between F3 and FP1, a location corresponding approximately to the left dorsolateral prefrontal cortex, and the cathode placed at the midpoint between T3 and P3, a location corresponding to left temporo-parietal junction. Placement and parameters in tDCS are consistent with Brunelin et al, 2012). Placement and parameters in tRNS are consistent with. Stimulation setup and administration takes approximately 30 minutes.