Half a century of research on the Stroop effect: An integrative review.

MacLeod, Colin M. · 1991 · OpenAlex-citations

DOI: 10.1037/0033-2909.109.2.163

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Summary

This integrative review by Colin M. MacLeod (1991) addresses the extensive literature on the Stroop Color-Word Task, spanning over 50 years and approximately 400 studies. The research was motivated by the need to organize this vast body of work, as previous reviews (e.g., Dyer, 1973) were deemed insufficient for contemporary cognitive psychology. MacLeod aims to create a taxonomy of empirical findings, evaluate existing theoretical explanations, and dispel myths surrounding the phenomenon. The review isolates 18 reliable empirical findings that any successful theory of the Stroop effect must account for, providing a critical benchmark for theoretical validity. The methodology involves a comprehensive synthesis of experimental data, focusing on the standard Stroop task where participants name the ink color of color words. The review categorizes studies into five sections: variations of the Stroop procedure, stimulus manipulations (individual trials and experiment-wide variables), response manipulations, and subject-related variables. MacLeod critically evaluates two major candidate theories: the relative speed of processing hypothesis and the automaticity of reading hypothesis. He assesses these theories against the isolated empirical findings, noting that earlier attempts to locate a single bottleneck in attention are inadequate. The review also contextualizes the Stroop effect within historical precedents, such as Cattell’s (1886) work on automatic versus voluntary processes, and examines the original experiments conducted by Stroop (1935), including replications that confirm the asymmetrical interference pattern where naming colors of incongruent words is significantly slower than reading words in incongruent colors. The main findings indicate that the two dominant theories—relative speed of processing and automaticity of reading—are "wanting" and fail to fully capture the critical evidence. Specifically, the review highlights that interference is robust and asymmetrical, with significant delays in color naming when words are incongruent, but negligible interference in word reading when ink colors are incongruent. MacLeod concludes that recent theories emphasizing the parallel processing of irrelevant and relevant dimensions are more likely to be successful than earlier bottleneck models. The review identifies specific empirical constraints, such as the effects of practice, stimulus characteristics, and subject variables, which must be integrated into any comprehensive theoretical framework. The significance of this work lies in its provision of a rigorous empirical foundation for future research on the Stroop effect. By isolating 18 reliable findings, MacLeod offers a clear set of criteria for evaluating new theories, moving the field beyond experiment-specific hypotheses toward a more comprehensive understanding of attention and interference. The review suggests that future research should focus on parallel processing models and provides directions for profitable inquiry, thereby refining the theoretical landscape of cognitive psychology. This integrative approach not only clarifies the historical development of the Stroop effect but also sets a standard for theoretical adequacy in explaining complex cognitive phenomena.

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• attention selective divided
• dual task multitasking

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• Theoretical Contribution: theory or model