Fig. 7.

The true positive rates of one word vs. all, estimated by a ten-fold cross validation method. Eliminating the covert articulation stage from analysis has less than 2% effect on grand average classification accuracy. Considering the Wilcoxon p value of 0.9269, compared to the high-Gamma linguistic processing stages, the contribution of motor imagery of articulation in class separation of covert speech tasks from EEG data is negligible