Typically, people have faster reaction times on congruent trials — when the right-pointing arrow actually appears on the right, and vice-versa.
It is obtained by subtracting responses to congruent trials from those to incongruent ones.
However, Costa et al.'s 2009 two experiments were divided as follows: the first one used two low-monitoring versions (92 and 8%% congruent trials), while the second one used two high-monitoring versions (50 and 75%% congruent trials).
With increasing age, overall performance across high-interference incongruent and low-interference congruent trials became faster and more accurate.
The congruency effect in distracter interference tasks is often reduced after incongruent as compared to congruent trials.
This would produce similar performance between congruent and incongruent trials, because the congruent trials no longer benefit from facilitation from the uncued half.
Since congruent trials offer no conflict, i.e., no irrelevant spatial information, faster RTs are expected, resulting in positive RTs for Simon effects.
On this matter, it is important to highlight that Costa et al. (2008) and Costa et al. (2009) used different percentages of congruent trials.
On the flanker task, a difference score was calculated by subtracting the mean reaction times for congruent trials from incongruent trials.
This was expressed by faster RTs associated with increased amygdala activity and activation of the ventral ACC, in congruent trials only.
Relative to pre-training, participants showed reduced reaction time (RT) and N2 amplitude for incongruent, but not congruent, trials, suggesting improved interference resolution.
