Recent work on cognitive control focuses on the conflict-monitoring hypothesis, which posits that a performance monitoring mechanism recruits regions in the dorsolateral prefrontal cortex to ensure that goal-directed behavior is optimal. Critical to this theory is that a single performance monitoring mechanism explains a large number of behavioral effects including the sequential congruency effect (SCE) and the error-related slowing (ERS) effect. This leads to the prediction that the size of these effects should correlate across cognitive control tasks. To this end, we conducted three large-scale individual differences experiments to examine whether the SCE and ERS effect are correlated across Simon, Flanker, and Stroop tasks. Across all experiments, the results revealed a correlation for the error-related slowing effect, but not for the sequential congruency effect across tasks. We discuss the implications of these results in regards to the hypothesis that a domain-general performance monitoring mechanism drives both effects. (PsycINFO Database Record (c) 2019 APA, all rights reserved).