A widespread view in cognition is that once acquired through extensive practice, mental skills such as reading are automatic. Lexical and semantic analyses of single words are said to be uncontrollable in the sense that they cannot be prevented. Over the past 60 years, apparently convincing support for this assumption has come from hundreds of experiments in which skilled readers have processed an irrelevant word in the Stroop task despite explicit instructions not to, even when so doing would hurt color identification performance. This basic effect was replicated in two experiments, which also showed that a considerable amount of semantic processing is locally controlled by elements of the task. For example, simply coloring a single letter instead of the whole word eliminated the Stroop effect. This outcome flies in the face of any automaticity account in which specified processes cannot be prevented from being set in motion, but it is consistent with the venerable idea that mental set is a powerful determinant of performance. 221Many low-level human behaviors are automatic, in that a stimulus serves to elicit the behavior in the absence of conscious awareness or intention (e.g., an eye blink in response to a puff of air; the patellar reflex; the Babinski reflex), Learned behaviors such as reading are also widely argued to be automatic in a similar sense. For example, it is well established that identifying the color of an incongruent word (e.g., green letters spelling the word "red") is slower than identifying the color of a congruent word (e.g., green letters spelling the word "green"). This Stroop effect (Stroop, 1935) and its many variants have been explored empirically, theoretically, and computationally by cognitive and developmental psychologists, psycholinguists, neuropsychologists, and cognitive scientists in more than 500 papers over the past 60 years (see MacLeod's 1991 review). A core assumption of virtually all the theoretical accounts is that skilled readers process the irrelevant word without consciousness or intent. Reading the word is said to be automatic in the sense that readers cannot refrain from computing the meaning of the word despite explicit instructions not to do SO:I Reading is such an automatic process that it is difficult to inhibit and it will interfere with processing other information about the word.