Relation between mean reaction time and size of memory set. Positive (top) and negative responses (bottom) are depicted during placebo (dotted line), anodal (continuous line) and cathodal (dashed line) tDCS stimulation (n = 12). For post-hoc t Tests data of both stimulation sessions were collapsed since they were practically identical (see text). Symbols indicate differences in reaction time between placebo and stimulation. ** p < 0.01, * p < 0.05, t p < 0.1.