In two experiments on Stroop interference, we examined whether sentences can be processed without the intention of the reader. Participants named the ink colors in which words in sentences were printed, and the ink colors in which the same words, randomly arranged, were printed. In Experiment 1, sentences yielded longer response times (RTs) and more errors than did nonsentences, but only when they included words that were highly relevant to the color-naming task (i.e., color and color-related words). In Experiment 2, sentences yielded more errors than did nonsentences, and sentences in which the color words matched the set of ink colors yielded longer RTs than did nonsentences. The results indicate that sentence processing can be obligatory when the component words are highly relevant to the task.In 1935, 1. R. Stroop reported a series of experiments that precipitated an explosion of research into what has since been called the Stroop effect. Stroop found that participants took significantly longer to name the ink colors in which incongruent color words were printed than to name the ink colors in which color squares were printed (Experiment 2). Words caused interference in the co10r-naming task.According to some explanations of the Stroop effect, individuals are so experienced at word reading that they do it without intention (e.g., Posner & Snyder, 1975). More recent accounts suggest that the interference evident in the Stroop task is due to vast differences in the relative strengths ofprocessing associated with word reading and color naming (Cohen, Dunbar, & McClelland, 1990). Processing strength results directly from practice and determines the level of attention that a process requires, the speed with which it can occur, and the interference effects that will emerge in dual-task situations. Word reading is a task practiced frequently; it occurs quickly and requires little attention. Color naming, on the other hand, is a task practiced less often; it therefore requires more time and conscious attention than does word reading.Because the word-reading and color-naming processes both rely on a common resource (i.e., a verbal response at the output stage), the Stroop task promotes response Earlier versions of this report were presented at the meeting of the Rocky Mountain