Most interestingly, there was a highly significant main effect CONDITION ( F [1,29] = 26.27, p < .001, partial- η 2 = .48), revealing generally stronger alpha-synchronization (or lower alpha-desynchronization, respectively) during task performance under high as compared to low internal processing demands (see Fig. 2 ).
While the four-way interaction (additionally involving TASK), however, failed to reach statistical significance ( p = .66), a follow-up univariate analysis (Greenhouse-Geisser corrected dfs) per task revealed a significant CONDITION × AREA × HEMISPHERE interaction only for the divergent task ( F [2.23,64.63] = 7.27, p < .001, partial- η 2 = .20) but not for the convergent task ( F [3.17,91.83] = 1.15, ns ., partial- η 2 = .04).