Visual word recognition is commonly argued to be automatic in the sense that it is obligatory and ballistic. The present experiments combined Stroop and visual search paradigms to provide a novel test of this claim. An array of three, five, or seven words including one colored target (a word in Experiments 1 and 2, a bar in Experiment 3) was presented to participants. An irrelevant color word also appeared in the display and was either integrated with or separated from the colored target. The participants classified the color of the single colored item in Experiments 1 and 3 and determined whether a target color was present or absent in Experiment 2. A Stroop effect was observed in Experiment 1 when the color word and the color target were integral, but not when the color word and the color target were separated. No Stroop effect was observed in Experiment 2. Visual word recognition is contingent on both the distribution of spatial attention and task demands.
A skilled reader is typically familiar with about 30,000 words and can recognize a visually presented word in less than half a second (Rayner & Pollatsek, 1989). A major approach to understanding this degree of fluency assumes that visual word recognition is automatic. As such, visual word recognition is argued to be obligatory and ballistic, in that it is triggered by the appearance of the stimulus in the visual field and runs to completion (i.e., activates semantics) independently of the observer's intentions. For example, Brown, Gore, and Carr (2002) asserted that
Visual word recognition is largely obligatory, in the sense that lexical processing is initiated by the presence of a word in the visual field, (p. 236)
Thus, a lexical object, present in the visual field, always activates its semantic representation in long-term memory. We therefore can expect that an obligatory process is (1) independent of spatial attention and (2) independent of the mental set of the participant, where mental set is defined as a state of preparedness, determined by context or the person's experience.
The Stroop effect is often cited as strong evidence for the obligatory nature of visual word recognition (Stroop, 1935; see also MacLeod, 1991, for a review). Participants are instructed to identify the display color of a letter string, and response latencies are longer when the print color and the color word are incongruent (e.g., the word red in blue), relative to when they are congruent (e.g., the word blue in blue) or neutral (e.g., the word house in blue). This result is interpreted as support for the hypothesis that visual word recognition is outside the control of the observer. The present investigation combines Stroop and visual search paradigms to provide a novel test of this claim.
In a visual search task, participants determine whether a target item is present among a set of distractors. Search times vary from efficient (response time [RT] × set size slope [asymptotically =] 0 msec/item) to very inefficient (RT × set size slope > 30 msec/item; see Wolfe, 1998). Targets producing efficient searches (e.g., featural singletons) are said to be processed in parallel across space, in that focused attention is not necessary to discriminate them from distractors. In contrast, targets producing inefficient searches (e.g., a conjunction of features) require that participants focus attention on each item in order to make the target/distractor discrimination (Treisman & Gormican, 1988). The efficiency of the search can, therefore, be interpreted as an index of the focused attention devoted to a distractor item. As Treisman and Gelade (1980) noted, if a display is searched in parallel, only those characteristics of the distractor items whose processing does not require spatial attention will influence responses to the target item. Therefore, if the meaning of a distractor word in a search task influences performance when parallel search is evident (i. …