Although this did not reach statistical significance (subthreshold cluster in frontal learning effect at 380–452 ms, p = 0.1311), it is tempting to speculate that this early effect could reflect differential processing of the cue as participants start to learn that it might be task relevant.
The difference between the regression slope for target cues and control cues showed a trend, but was not significant (mean over 588–780 ms, t 17 = -1.84, p = 0.083).
There is also a significant difference between target cue and control cue potentials in the second half of the session (568–772 ms, one-tailed comparison cluster p = 0.047), confirming that the learning effect was larger for target cues than for control cues (even though the regression effect above showed only a trend toward significance).