The locus of interference in the Stroop and related tasks

Perceptual conflict and response competition interpretations of studies of color-word interference are briefly considered, and a study of the effect of semantic factors on color-word interference in a color comparison task is reported. It is concluded that the locus or interference is after, and not during, the processing of the word component of color-word stimuli.     

STROOP INTERFERENCE AND COLOR-WORD SIMILARITY

Abstract— Stroop interference refers to the finding that it takes longer to name the color of an incongruent color (e g, the word blue shown in green) than it does to name the color of a neutral stimulus (e g, a series of number signs shown in green) Incongruent color-word stimuli can differ in the similarity between the color in which the word is printed and the color denoted by the word (e g, the ward blue shown in green vs yellow) This research shows that the amount of interference obtained is related to color-word similarity, suggesting that word-reading and color-naming processes interact at a conceptual level prior to response emission.     

Hemispheric differences in picture-word interference

In a picture-word version of the Stroop task, 30 right-handed subjects were tested under each of six conditions in which a picture alone or a picture plus a word were presented to the left, the right, or both hemispheres. In two additional conditions the picture was presented to the right hemisphere and the word was simultaneously presented to the left hemisphere, or vice versa. For all conditions, subjects were instructed to name the picture only, as rapidly as possible. Picture naming times were significantly slower for the conditions in which the pictures were accompanied by words than in the respective picture alone conditions. Moreover, simultaneous presentation of a picture and a word to both hemispheres resulted in greater interference (slower picture naming times) than did the simultaneous presentation of the picture and the word to either the left hemisphere alone or the right hemisphere alone. The latter two conditions, in turn, resulted in significantly more interference than did the simultaneous presentation of the picture to one hemisphere and the word to the other hemisphere. This pattern of results suggests that the Stroop effect obtained under normal circumstances is in large part a function of the interference caused by the simultaneous processing of items in the same hemisphere. In contrast to hemispheric differences reported for the color-word Stroop task, the effect of presenting a picture and word simultaneously to the right hemisphere did not differ reliably from that of presenting a picture and word to the left hemisphere. The failure to replicate this aspect of the color-word Stroop is attributed to differences in the abilities of the two hemispheres to process the respective target items (the color or the picture) of the two tasks.     

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.     

Semantic Competition as the Basis of Stroop Interference:Evidence From Color-Word Matching Tasks

Abstract—A color-word matching task was used to investigate the basis of Stroop interference. Subjects were shown a pair of stimuli: an ink color (e.g., a red bar) and a colored word (e.g., RED printed in red or blue) and decided whether the two items had the same meaning (meaning decisions) or whether they had the same surface color (visual decisions). In Experiment 1, the two stimuli were shown simultaneously, and conflicting visual information of the word (e.g., RED printed in blue, against a red bar) led to interference in meaning decisions, whereas conflicting verbal information (e.g., BLUE printed in red, against a red bar) produced no interference in visual decisions. In Experiment 2, as an increasing time interval was imposed between presentation of the color bar and the colored word, interference in meaning decisions diminished, whereas interference in visual decisions was established. These results suggest that semantic competition, not response competition, is the major source of Stroop and Stroop-like interference.     

Attention, temporal predictability, and the time course of context effects in naming performance

Models of attention and context effects in naming performance should be able to account for the time course of color-word Stroop interference revealed by manipulations of the stimulus onset asynchrony (SOA) between color and word. Prominent models of Stroop task performance ( [Cohen et al., 1990], [Cohen and Huston, 1994] and [Phaf et al., 1990]) fail to account for the fact that response time (RT) and Stroop interference peak at zero SOA and diminish with word preexposure. The models may be saved by assuming that the time course of interference is determined by a strategic orienting of attention to color onsets when SOA is predictable. To test this temporal predictability hypothesis, SOA was blocked or randomly mixed in Experiment 1. In addition, the time interval between color onsets was randomly variable in Experiment 2. Although RTs were affected, none of the randomization manipulations influenced the typical shape of the time course of Stroop effects. These findings provide evidence against the temporal predictability hypothesis and thereby against prominent models of the Stroop task.     

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.     

Reduced Stroop interference for opponent colors may be due to input factors: evidence from individual differences and a neural network simulation

Sensory or input factors can influence the strength of interference in the classic Stroop color-word task. Specifically, in a single-trial computerized version of the Stroop task, when color-word pairs were incongruent, opponent color pairs (e.g., the word BLUE in yellow) showed reduced Stroop interference compared with nonopponent color pairs (e.g., BLUE in red). In addition, participants' color discrimination ability was measured by standard color vision tests (i.e., Farnsworth-Munsell 100-Hue Test and Ishihara plates). Error rates in the Farnsworth-Munsell test correlated positively with the amount of Stroop interference. Neural network simulations (variants of J. D. Cohen, K. Dunbar, & J. L. McClelland's, 1990, model) showed that only a distributed trichromatic input layer was able to simulate these findings. Thus, sensory input from the color system needs to be incorporated into current accounts of the Stroop effect.     

用PDP模型模拟Stroop任务的实验研究

本实验用基于ＰＤＰ原理构造的Ｓｔｒｏｏｐ任务模型模拟了Ｓｔｒｏｏｐ颜色－词的干扰现象。模型采用ＢＰ学习算法。经过训练,模型学会字词阅读和颜色命名。由于对模型采用６种不同的学习次数（这里为：５００,１０００,２０００,３０００,５０００,１００００）以及４种不同比例（这里为：４：１,６：１,８：１,１０：１）字词模式和颜色模式的训练,其结果字词通道的信息加工比颜色通道的加工更快更强,并产生不同的干扰模式,其字词加工的次数越多,干扰越大,次数越少,干扰也越小。这很可能说明语言的熟练程度对干扰模式有着更大的影响。模型还体现了加工过程的连续性质。但这个模型难以区分不同的加工任务。     

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。     

Interference control in children with reading difficulties

Two studies investigated whether the greater Stroop interference reported in children with reading difficulties compared to typical readers of the same age represents a generalized deficit in interference control or a consequence of their reading problems. In Study 1, a color-word Stroop task and a nonverbal task involving responses to locations associated with pictures were administered to 23 children with single word reading difficulties and 22 typically developing children matched for age and nonverbal ability. Children with reading difficulties showed disproportionate interference effects in the color-word Stroop but not the nonverbal task. In Study 2, groups of poor and typical readers completed a spatial Stroop task with printed input that did not require a verbal response and a nonverbal analogue. Both groups showed comparable interference in these two tasks. Thus, the reported problems in the color-word Stroop task in children with reading difficulties do not appear to entail general impairments in interference control.     

Coloring only a single letter does not eliminate color-word interference in a vocal-response Stroop task: automaticity revealed

The presence of an interference effect in naming the print color of color words (J. R. Stroop, 1935) suggests that responses associated with the irrelevant-word dimension of the display are activated involuntarily. In the present study, the author examined the conditions under which coloring a single letter in a word reduced interference in vocal responding (D. Kahneman & A. Henik, 1981) or eliminated it in manual responding (D. Besner, J. A. Stolz, & C. Boutilier, 1997). In Experiment 1, color-word interference was significant under vocal responding for the Besner et al. displays. In Experiment 2, the author replicated the Kahneman and Henik effect with the Besner et al. stimuli. The results of Experiment 3 showed that semantic effects are not eliminated by coloring only a single letter. Coloring a single letter does not prevent the activation of the irrelevant-word dimension of the colored color word.     

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.     

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.     

Category learning in the color-word contingency learning paradigm

In the typical color-word contingency learning paradigm, participants respond to the print color of words where each word is presented most often in one color. Learning is indicated by faster and more accurate responses when a word is presented in its usual color, relative to another color. To eliminate the possibility that this effect is driven exclusively by the familiarity of item-specific word-color pairings, we examine whether contingency learning effects can be observed also when colors are related to categories of words rather than to individual words. To this end, the reported experiments used three categories of words (animals, verbs, and professions) that were each predictive of one color. Importantly, each individual word was presented only once, thus eliminating individual color-word contingencies. Nevertheless, for the first time, a category-based contingency effect was observed, with faster and more accurate responses when a category item was presented in the color in which most of the other items of that category were presented. This finding helps to constrain episodic learning models and sets the stage for new research on category-based contingency learning.     

The spatial Stroop effect: A comparison of color-word and position-word interference

The Stroop effect is one of the most famous examples of interference in human perception. The present study demonstrates that a position Stroop paradigm, comparable to the classical color-word interference paradigm, resulted in the same pattern of interference for the spatial dimension; however, the interference was significantly weaker. By exchanging the original oral response for a manual response in the spatial paradigm, we showed that the verbal component is crucial for the Stroop effect: Manual responses lead to a disappearance of the interference effect. Moreover, with manual responses word position was recognized at the same speed for the baseline condition and for words that were incongruent as well as congruent with the spatial position. The results indicate (1) that the Stoop effect depends heavily on verbal components and (2) that differing processing speeds between reading and position recognition do not serve as a proper explanation for the effect. In addition, the provided paradigm plausibly transfers the classical color-word interference to the spatial dimension.     

Coloring Only a Single Letter Does Not Eliminate Color-Word Interference in a Vocal-Response Stroop Task: Automaticity Revealed

The presence of an interference effect in naming the print color of color words (J. R. Stroop, 1935) suggests that responses associated with the irrelevant-word dimension of the display are activated involuntarily. In the present study, the author examined the conditions under which coloring a single letter in a word reduced interference in vocal responding (D. Kahneman & A. Henik, 1981) or eliminated it in manual responding (D. Besner, J. A. Stolz, & C. Boutilier, 1997). In Experiment 1, color-word interference was significant under vocal responding for the Besner et al. displays. In Experiment 2, the author replicated the Kahneman and Henik effect with the Besner et al. stimuli. The results of Experiment 3 showed that semantic effects are not eliminated by coloring only a single letter. Coloring a single letter does not prevent the activation of the irrelevant-word dimension of the colored color word.     

Self-monitoring,need for cognition,and the Stroop effect: a preliminary study

The color-word Stroop task requires an individual to ignore one piece of information (word) while responding to another (color). Since self-monitors are good at adapting their responses to fit a situation and those high in need for cognition carefully think through information before responding, this study explored the relationship between self-monitoring and need for cognition using Stroop interference. It was anticipated that self-monitoring would reduce Stroop interference, while need for cognition would increase Stroop interference. 23 General Psychology students (10 men, 13 women, M(age) = 18.8 yr.) participated. Participants were given the Self-monitoring Scale, the Need for Cognition Scale, and the Stroop Color-Word Test. Analysis indicated that Need for Cognition was not correlated with Stroop interference (r = .31) but higher scores on Self-monitoring were correlated with lower Stroop interference (r = .43). Implications for research are suggested.     

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.     

Age-related trends of interference control in school-age children and young adults in the Stroop color-word test

In this cross-sectional study, differences in interference control, one component of executive function, were investigated among three age groups, 15 early childhood (7- to 8-yr.-olds), 25 middle childhood (9- to 12-yr.-olds), and 20 young adults (21- to 30-yr.-olds). Participants were administered a computer version of the Stroop color-word test with an oral response; correct responses, response time (RT), and the interference ratio were examined. The data indicated that (1) most of the participants showed no errors in word reading, color-naming, and incongruent color-naming tasks; (2) in word-reading and color-naming tasks, RT for 7- to 8-yr.-olds was longer than that for 9- to 12-yr.-olds, while RT of 9- to 12-yr.-olds and young adults were comparable; (3) in an incongruent color-naming task, RT for 7- to 8-yr.-olds was longer than RT for 9- to 12-yr.-olds, which was longer than RT for young adults; and (4) the interference ratio was higher in 7- to 8-yr.-olds than in 9- to 12-yr.-olds, which was higher than in young adults. These results suggested the difference in interference control between early and middle childhood reported on the go/no-go task and the stop-signal procedure would be observed in the Stroop color-word paradigm as well. The utility of this modified Stroop color-word test for those with intellectual and developmental disabilities was discussed.