Demographic characteristics across the three stimulation groups.

<p>Values are presented as mean ± standard error of the mean. Participants across the three stimulation groups did not differ in terms of age (p = 0.19, ANOVA), time required in completing the mental set phase (p = 0.76, ANOVA) or experience in a quantitative field (p = 0.85, 2 tailed Fisher's exact test). It turned out that gender is not evenly distributed across the stimulation groups, with a few more females in the sham stimulation group. Nevertheless, it is clear from the data that gender is not a predictor of success in problem solving for either the Type 2 (p = 1, 2-tailed Fisher's exact test) or Type 3 (p = 0.58, 2-tailed Fisher's exact test) insight problem (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016655#pone-0016655-t002" target="_blank">Table 2</a>).