The time-course of distractor-based activation modulates effects of speed-accuracy tradeoffs in conflict tasks

Mittelstädt, Victor; Miller, Jeff; Leuthold, Hartmut; Mackenzie, Ian Grant; Ulrich, Rolf · 2021 · OpenAlex-citations

DOI: 10.3758/s13423-021-02003-x

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Summary

This study investigates how speed-accuracy tradeoffs (SATs) influence decision-making in the presence of conflicting information, specifically comparing the Simon task (spatial conflict) and the Eriksen flanker task (feature conflict). While evidence accumulation models typically explain SATs via adjustments to decision boundaries, it remains unclear how these mechanisms account for opposing effects observed in previous literature: the Simon congruency effect often increases under speed pressure, whereas the Eriksen congruency effect decreases. The authors hypothesized that the time-course of distractor-based activation differs between these tasks, modulating the impact of strategic boundary adjustments. In a single preregistered experiment, 32 participants performed alternating blocks of Simon and Eriksen tasks under either speed-focused or accuracy-focused instructions. The Simon task required responding based on stimulus identity while ignoring location, while the Eriksen task required ignoring flanking letters. Reaction times (RTs) and error rates were recorded, and data were analyzed using distributional delta plots to examine the unfolding of congruency effects over time. Additionally, the authors fitted the Diffusion Model for Conflict (DMC) to the data to quantify the temporal dynamics of distractor activation and decision parameters. The results confirmed opposing SAT effects on mean RT congruency: the Simon effect increased under speed pressure (32 ms) compared to accuracy focus (13 ms), whereas the Eriksen effect decreased under speed pressure (32 ms) compared to accuracy focus (43 ms). Delta plot analyses revealed distinct temporal patterns: Eriksen delta plots generally increased across the RT distribution, indicating late-arriving distractor interference, while Simon delta plots decreased for slower responses, indicating early-arriving interference. DMC modeling successfully accounted for these patterns, revealing that distractor activation peaked significantly earlier in the Simon task (~45–57 ms) than in the Eriksen task (~113–128 ms). Under speed pressure, participants lowered decision boundaries and reduced non-decision times. Because Simon distractor activation peaks early, lowering boundaries captures more of this interference, increasing the congruency effect. Conversely, because Eriksen distractor activation peaks late, lowering boundaries allows decisions to be made before the distractor influence fully develops, decreasing the congruency effect. These findings demonstrate that the strategic adjustment of decision boundaries interacts with the specific time-course of distractor-based activation to produce task-dependent outcomes. The study validates the DMC model’s ability to capture these dynamics and highlights that SAT manipulations have multiple, interacting effects on cognitive processes. This clarifies previous contradictory findings by showing that the temporal profile of irrelevant information is a critical determinant of how speed-accuracy strategies affect performance in conflict tasks.

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• time perception