The Relationship between Stroop and Stop-Signal Measures of Inhibition in Adolescents: Influences from Variations in Context and Measure Estimation

The Stroop and stop-signal tasks are commonly used to index prepotent response inhibition in studies of cognitive development and individual differences. Inhibitory measures from the two tasks have been derived using a variety of methods. Findings of low inter-correlations amongst these measures have been interpreted as evidence for different kinds of inhibitory functions. Our previous study found Stroop and stop-signal accuracy measures to be uncorrelated and they loaded on different inhibitory components in a principal component analysis. The present study examined whether this finding is replicated across different task contexts, derived measures, and methods of derivation. Adolescents (N = 247) were administered a number-quantity Stroop and word and number stop-signal tasks. For each stop-signal task, inhibitory efficiency was estimated using a stop-signal reaction time measure estimated with the central versus the integration methods. For the Stroop interference task, inhibitory efficiency was indexed by reaction time measures (including inverse efficiency scores) generated from difference scores and regression residuals, and delta-plot slopes. The reaction time measures from the two tasks were generally not correlated. The only exception was that Stroop inhibitory ability, indexed by Stroop errors, was related to stop-signal inhibitory efficiency, indexed by stop-signal reaction time. These findings are consistent with previous findings suggesting that measures from the Stroop and stop-signal tasks are influenced by different underlying processes. The impact of variations in dependent measure derivation on the resulting reliabilities of Stroop and stop-signal measures and on observed correlations between them were examined. Variables that may have contributed to the null findings are discussed.