We extracted the mean amplitude in the 100–140 ms interval as a
measure of mismatch negativity (Fig. 1). These values were subjected
to a Wilcoxon signed-rank test, to test for differences across the
difference waves in the four stimulus conditions. Here, the normal,
upright condition proved significantly different from the other three
conditions (P0.70 for each comparison). This again suggests a high
sensitivity of the McGurk-MMN to Thatcherization and inversion