The article provides an integrative review of over 50 years of research on the Stroop effect, covering approximately 400 studies. The author, Colin M. MacLeod, organizes and evaluates existing theoretical positions, concluding that recent theories emphasizing parallel processing of irrelevant and relevant dimensions are more successful than earlier theories focusing on a single bottleneck in attention. The review traces the roots of the Stroop effect back to James McKeen Cattell's work in 1886, highlighting the influence of his automatic/voluntary distinction on subsequent research. The article then delves into the original Stroop study, detailing the experimental design and findings, and discusses various variations of the Stroop task, including the color-word interference test, individual stimulus versions, sorting and matching tasks, and auditory analogs. It also explores other analogs such as the flanker task and tasks involving shapes, arrows, numerosity, and global versus local features. The review concludes with a summary of empirical findings that must be accommodated by any viable theory of the Stroop effect, emphasizing the robustness and complexity of the phenomenon.The article provides an integrative review of over 50 years of research on the Stroop effect, covering approximately 400 studies. The author, Colin M. MacLeod, organizes and evaluates existing theoretical positions, concluding that recent theories emphasizing parallel processing of irrelevant and relevant dimensions are more successful than earlier theories focusing on a single bottleneck in attention. The review traces the roots of the Stroop effect back to James McKeen Cattell's work in 1886, highlighting the influence of his automatic/voluntary distinction on subsequent research. The article then delves into the original Stroop study, detailing the experimental design and findings, and discusses various variations of the Stroop task, including the color-word interference test, individual stimulus versions, sorting and matching tasks, and auditory analogs. It also explores other analogs such as the flanker task and tasks involving shapes, arrows, numerosity, and global versus local features. The review concludes with a summary of empirical findings that must be accommodated by any viable theory of the Stroop effect, emphasizing the robustness and complexity of the phenomenon.