The dynamics of measurement in conflict paradigms

Attentional control is commonly measured using conflict paradigms such as the Flanker, Simon, and Stroop tasks, which consistently yield large group-level congruency effects. The reliability of individual-difference estimates derived from these tasks, however, remains less certain. Increasing interference demands, as in squared conflict paradigms, may improve the precision of individual-difference estimates. The reliability of both group- and individual-level estimates may also vary as a function of testing duration. We examined the relationship between cumulative testing time and the reliability of group- and individual-level estimates. Participants completed 10 short blocks of a single squared conflict paradigm (Flanker Squared, Simon Squared, or Stroop Squared). First, we quantified the magnitude of the group-level congruency effect by computing Bayes factors sequentially across cumulative blocks, identifying the point at which additional testing yields diminishing returns for group-level inference. Second, we evaluated the reliability of individual-differences using hierarchical mixed-effects models fit to trial-level response times, examining how the variance and stability of individual congruency estimates evolve as additional blocks are included. Together, these findings characterise conflict tasks as dynamic measurement systems in which the precision of both group- and individual-level estimates changes as data accumulates. Formalising the relationship between effect size and testing duration may guide the development of more efficient and psychometrically robust assessments of attentional control.