The visual-auditory color-word Stroop asymmetry and its time course

Four experiments examined crossmodal versions of the Stroop task in order (1) to look for Stroop asymmetries in color naming, spoken-word naming, and written-word naming and to evaluate the time course of these asymmetries, and (2) to compare these findings to current models of the Stroop effect. Participants named color patches while ignoring spoken color words presented with an onset varying from 300 msec before to 300 msec after the onset of the color (Experiment 1), or they named the spoken words and ignored the colors (Experiment 2). A secondary visual detection task assured that the participants looked at the colors in both tasks. Spoken color words yielded Stroop effects in color naming, but colors did not yield an effect in spoken-word naming at any stimulus onset asynchrony. This asymmetry in effects was obtained with equivalent color- and spoken-word-naming latencies. Written color words yielded a Stroop effect in naming spoken words (Experiment 3), and spoken color words yielded an effect in naming written words (Experiment 4). These results were interpreted as most consistent with an architectural account of the color-word Stroop asymmetry, in contrast with discriminability and pathway strength accounts.     

Context effects in stroop-like word and picture processing

Presents a series of 6 experiments in which Stroop-like effects were generated by modally pure color-color, picture-picture, and word-word stimuli instead of the usual modally mixed color-word or picture-word stimuli. Naming, reading, and categorization tasks were applied. The Stroop inhibition was preserved with these stimuli but unexpectedly showed a semantic gradient only in the naming and not in the reading task. Word categorizing was slower and more interference prone than picture categorizing. These and other results can be captured by a model with two main assumptions: (a) semantic memory and the lexicon are separate, and (b) words have privileged access to the lexicon, whereas pictures and colors have privileged access to the semantic network. Such a model is developed and put to an initial test.     

A Stroop-like effect in color-naming of color-word lexigrams by a chimpanzee (Pan troglodyte)

The Stroop effect (J. R. Stroop, 1935) reflects the difficulty in ignoring irrelevant, but automatically processed, semantic information that is inherent in certain stimuli. With humans, researchers have found this effect when they asked participants to name the color of the letters that make up a word that is incongruent with that color. The authors tested a chimpanzee that had learned to associate geometric symbols called lexigrams with specific colors. When the chimpanzee had to make different responses that depended on the color of stimuli presented to her, she showed a Stroop-like effect when researchers presented to her the previously learned symbols for colors in incongruent font colors. Her accuracy performance was significantly poorer with these stimuli than with congruent color-referent lexigrams, noncolor-referent lexigrams, and nonlexigram stimuli, although there were not any significant differences in response latency. The authors' results demonstrated color-word interference in a Stroop task with a nonhuman animal.     

Sentence interference in the Stroop task

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.     

Stroop Interference,Practice, and Aging

We report two experiments that investigate practice effects on Stroop color-word interference in older and younger adults. Both experiments employed a computerized, single-item version of the Stroop task with a voice response, and both involved practice over hundreds of trials. Both experiments showed generally similar practice patterns, including a practice-related reduction in the size of the color-word interference effect. However, the older group continued to show a larger interference effect throughout practice. These findings indicate that older adults show the same trend in practice-related improvement on the Stroop task as younger adults.     

A reversal of the Stroop interference effect,through scanning:

Interference on the Stroop test has been explained on the basis of a stronger habit (word reading) interfering with a weaker one (color naming) on an incongruous color-word (CW) card. Since scanning for words is slower (weaker) than scanning for colors, it was predicted that making the Stroop a scanning task would produce more interference with scanning for words rather than colors on the CW card. This prediction was confirmed. In addition, analyses of individual differences offered some support for differential habit-strength theories of Stroop interference. However, differences between the standard and scanning Stroop tests suggested that some kind of information-processing analysis would be more fruitful.     

Stroop interference, practice, and aging

We report two experiments that investigate practice effects on Stroop color-word interference in older and younger adults. Both experiments employed a computerized, single-item version of the Stroop task with a voice response, and both involved practice over hundreds of trials. Both experiments showed generally similar practice patterns, including a practice-related reduction in the size of the color-word interference effect. However, the older group continued to show a larger interference effect throughout practice. These findings indicate that older adults show the same trend in practice-related improvement on the Stroop task as younger adults.     

Time course analysis of the Stroop phenomenon

Dyer (1971) investigated the response competition hypothesis of the Stroop phenomenon by temporally separating the color and word components of single stimuli (incongruent, control, and congruent). This line of research was continued in a series of five experiments that generalized Dyer's study: (a) In addition to the color-naming task, a reading task was included; (b) the irrelevant stimulus component was presented before and after the relevant one; (c) the probabilities of congruent and incongruent stimuli were varied; (d) besides color-word/color stimuli, color-color and word-word stimuli were used; and (e) the functional discrimination (color naming or reading) was compared with a sequential discrimination task. The data suggest the following temporal relations: (a) a slow facilitation due to response bias; (b) its inhibitory counterpart; and (c) a fast, strong inhibition with no facilitatory complement that seems to correspond to the usual Stroop conflict but that seems to occur earlier than the response execution stage.     

材料类型和颜色典型性影响颜色-物体Stroop效应

通过两个实验考查材料类型和颜色典型性对颜色-物体Stroop效应的影响。实验1,考查颜色-物体（图片）Stroop效应。结果颜色典型性差异显著,命名图片的颜色和图片的名称都产生显著的颜色-物体Stroop效应。实验2,考查颜色-物体（词语）Stroop效应。结果颜色典型性差异显著,命名词语的颜色产生颜色-物体Stroop效应,命名词语的名称未产生颜色-物体Stroop效应。结论,材料类型和颜色典型性影响颜色-物体Stroop效应。     

Translation and competition among internal representations in a reverse Stroop effect

In two experiments, the contributions of internal and external competition in a task known to produce a reverse Stroop effect were investigated. In this paradigm, the verbal meaning of an incongruent Stroop stimulus is identified by pointing to a patch of matching color--a task made difficult by the incongruent print color. The experiments showed that there was somewhat more interference when the (irrelevant) color in which the target word was printed was available as an alternate response patch than when it was not. However, significantly more interference was determined by whether the (irrelevant) print color belonged to the set of colors actually used as target words in the course of the experiment. Moreover, the same patterns of interference emerged when the task was altered so that the mere presence of the correct color had to be indicated with a keypress, rather than by pointing to the color's location. Consistent with translation models of Stroop interference, these results demonstrate the theoretical importance of competition among internal representations, rather than among stimuli or responses.     

Interactions between stimulus-stimulus congruence and stimulus-response compatibility

According to a central claim of Kornblum's dimensional-overlap model, response-related processes do not start before stimulus-related processes have been completed, which implies an additive relationship between effects of stimulus-stimulus congruence and stimulus-response compatibility. Three experiments were conducted to test this prediction. In Exp. 1, additive effects of color-word congruence (Stroop effect) and irrelevant spatial S-R compatibility (Simon effect) were in fact obtained. However, interactions between congruence and compatibility were observed in Exp. 2, where flanker-target congruence was varied, and in Exp. 3, where inter-level congruence of multi-level letters was manipulated. It is argued that these findings are inconsistent with the seriality assumption of the dimensional-overlap model, but that they support models claiming a temporal overlap of stimulus and response processing instead.     

Coloring an action: Intending to produce color events eliminates the Stroop effect

The implications of an ideomotor approach to action control were investigated. In Experiment 1, participants made manual responses to letter stimuli and they were presented with response-contingent color patches, i.e., colored action effects. This rendered stimuli of the same color as an action's effect effective primes of that action, suggesting that bilateral associations were created between actions and the effects they produced. Experiment 2 combined this set-up with a manual Stroop task, i.e., participants responded to congruent, neutral, or incongruent color-word compounds. Standard Stroop effects were observed in a control group without action effects and in a group with target-incompatible action effects, but the reaction time Stroop effect was eliminated if actions produced target-compatible color effects (e.g., blue word --> left key --> blue patch). Experiment 3 did not replicate this interaction between target-effect compatibility and color-word congruency with color words as action effects, which rules out semantically based accounts. Theoretical implications for both action-effect acquisition and the Stroop effect are discussed. It is suggested that learning action effects, the features of which overlap with the target, allows and motivates people to recode their actions in ways that make them more stimulus-compatible. This provides a processing shortcut for translating the relevant stimulus into the correct response and, thus, shields processing from the impact of competing word distractors.     

Examination stress and performance on a color-word interference test

Interference observed in the Stroop color-word task is influenced by various characteristics of the words employed. 38 students in their final year, approaching examinations, were asked to name the colors of words associated with this theme. These words produced greater delay than a control set, and those students who were most anxious about the examinations experienced most interference. This effect might be more generally employed in stress research, providing a performance-based index of reaction to issues or situations which are potential sources of anxiety.     

An Hebrew language version of the Stroop test

We present normative data from a Hebrew language version of the Stroop color-word test. In this sample of college-educated Israeli young adults, 18 women and 28 men with a mean age of 28.4 yr. completed a Hebrew language Stroop test. When compared with 1978 English language norms of Golden, Hebrew speakers were slower on color-word reading and color naming, similar on naming the color of incongruently colored names of colors, and showed less interference. Slowed color-word reading and color-naming may reflect the two-syllable length of the Hebrew names for one-syllable length English language colors; reduced interference may reflect the exclusion of vowels in much Hebrew printing and subjects' ability to provide competing, nonconflicting words while naming the color of words in which the hue and the lexical content do not match.     

Verbal coding and the elimination of Stroop interference in a matching task

Translational models of the Stroop effect (Virzi & Egeth, 1985) predict that Stroop interference can be eliminated if subjects can be induced to process target colors using a coding system separate from the coding system used to process distractors. This hypothesis was tested in two experiments. In the first experiment, we attempted to eliminate the need for subjects to translate target colors to verbal codes when responding to Stroop stimuli. Before responding to verbal incongruent color word distractors, subjects practiced matching colors to irregular shapes. It was expected that subjects would use nonverbal codes to mediate responding in this task. After practice, subjects continued the matching task in the presence of incongruent color words. Stroop interference persisted, contrary to predictions. Because subjects reported adopting verbal strategies to perform the matching task, Experiment 2 was designed to control the verbal coding strategies that subjects employed. Before responding to Stroop distractor stimuli, subjects in the nonsense name group practiced using nonsense names to mediate the matching of shapes to colors; subjects in the actual name group used actual color names to mediate performance in the matching task. When incongruent color word distractors were introduced, Stroop interference was eliminated for subjects in the nonsense name group, but persisted for subjects in the actual name group. The results are interpreted as consistent with an outcome conflict (Navon & Miller, 1987) or a modified translational model of the Stroop effect.     

Filling a gap in the semantic gradient: Color associates and response set effects in the Stroop task

In the Stroop task, incongruent color associates (e.g., LAKE) interfere more with color identification than neutral words do (e.g., SEAT). However, color associates have historically been related to colors in the response set. Response set membership is an important factor in Stroop interference, because color words in the response set interfere more than color words not in the response set. It has not been established whether response set membership plays a role in the ability of a colorassociate to interfere with color identification. This issue was addressed in two experiments (one using vocal responses and one using manual responses) by comparing the magnitude of interference caused by color associates related to colors in the response set with that of interference caused by color associates unrelated to colors in the response set. The results of both experiments show that color associates unrelated to colors in the response set interfered with color identification more than neutral words did. However, the amount of interference was less than that from color associates that were related to colors in the response set. In addition, this pattern was consistent across response modalities. These results are discussed with respect to various theoretical accounts of Stroop interference.     

Comparing color-word and picture-word Stroop-like effects: A test of the Glaser and Glaser (1989) model

Summary Glaser and Glaser (1989) assume that the processing of colors and pictures is highly similar in that, compared to words, both kinds of stimulis have privileged access to semantic information. This assumption was tested in the present research. In Experiment 1, the season corresponding to the color or to the word of color-word Stroop stimuli had to be named (e.g., green for spring). In Experiment 2, subjects had to name the season corresponding to the picture or the word of a picture-word stimulus (e. g., flower for spring). According to Glaser and Glaser (1989), privileged semantic processing of colors and pictures should be evidenced by a larger interfering power of color and picture distractors than of word distractors. However, the asymmetric pattern of interference was observed only with picture-word stimuli (Experiment 2), but not with color-word stimuli (Experiment 1), suggesting that, unlike pictures, colors do not have privileged access to semantic information. It was also found that word distractors interfered with the semantic processing of pictures, a result that is incompatible with the dominance rule postulated by Glaser and Glaser (1989). From these results, an adapted version of the Glaser and Glaser model is proposed: colors are assumed to have privileged access to a separate color processing system and the pattern of interference depends upon the relative activation strength of the response alternatives activated by the target and the distractor.     

Suggestion does not de-automatize word reading: Evidence from the semantically based Stroop task

Recent studies have shown that the suggestion for participants to construe words as meaningless symbols reduces, or even eliminates, standard Stroop interference in highly suggestible individuals (Raz, Fan, & Posner, 2005; Raz, Kirsch, Pollard, & Nitkin-Kaner, 2006). In these studies, the researchers consequently concluded that this suggestion de-automatizes word reading. The aim of the present study was to closely examine this claim. To this end, highly suggestible individuals completed both standard and semantically based Stroop tasks, either with or without a suggestion to construe the words as meaningless symbols (manipulated in both a between-participants [Exp. 1] and a within-participants [Exp. 2] design). By showing that suggestion substantially reduced standard Stroop interference, these two experiments replicated Raz et al.'s (2006) results. However, in both experiments we also found significant semantically based Stroop effects of similar magnitudes in all suggestion conditions. Taken together, these results indicate that the suggestion to construe words as meaningless symbols does not eliminate, or even reduce, semantic activation (assessed by the semantically based Stroop effect) in highly suggestible individuals, and that such an intervention most likely reduces nonsemantic task-relevant response competition related to the standard Stroop task. In sum, contrary to Raz et al.'s claim, suggestion does not de-automatize or prevent reading (as shown by a significant amount of semantic processing), but rather seems to influence response competition. These results also add to the growing body of evidence showing that semantic activation in the Stroop task is indeed automatic.     

Emotional valence and physical space: limits of interaction

According to the body-specificity hypothesis, people associate positive things with the side of space that corresponds to their dominant hand and negative things with the side corresponding to their nondominant hand. Our aim was to find out whether this association holds also true for a response time study using linguistic stimuli, and whether such an association is activated automatically. Four experiments explored this association using positive and negative words. In Exp. 1, right-handers made a lexical judgment by pressing a left or right key. Attention was not explicitly drawn to the valence of the stimuli. No valence-by-side interaction emerged. In Exp. 2 and 3, right-handers and left-handers made a valence judgment by pressing a left or a right key. A valence-by-side interaction emerged: For positive words, responses were faster when participants responded with their dominant hand, whereas for negative words, responses were faster for the nondominant hand. Exp. 4 required a valence judgment without stating an explicit mapping of valence and side. No valence-by-side interaction emerged. The experiments provide evidence for an association between response side and valence, which, however, does not seem to be activated automatically but rather requires a task with an explicit response mapping to occur.     

A horse race of a different color: Stroop interference patterns with transformed words

Four experiments investigated Stroop interference using geometrically transformed words. Over experiments, reading was made increasingly difficult by manipulating orientation uncertainty and the number of noncolor words. As a consequence, time to read color words aloud increased dramatically. Yet, even when reading a color word was considerably slower than naming the color of ink in which the word was printed, Stroop interference persisted virtually unaltered. This result is incompatible with the simple horse race model widely used to explain color-word interference. When reading became extremely slow, a reversed Stroop effect--interference in reading the word due to an incongruent ink color--appeared for one transformation together with the standard Stroop interference. Whether or not the concept of automaticity is invoked, relative speed of processing the word versus the color does not provide an adequate overall explanation of the Stroop phenomenon.