Training on integrated versus separated Stroop tasks: The progression of interference and facilitation

Two experiments examined the course of interference and facilitation in the Stroop (1935) task during training. Two versions of the task were compared: integrated (e.g., the word RED in the color green) and separated (e.g., green asterisks above the word RED). Stimuli were congruent (RED in red), incongruent (GREEN in red), or neutral (XXX in red). Over 5-day (Experiment 1) and 10-day (Experiment 2) training sessions, facilitation due to congruence was small, stable, and equivalent in both task versions. In contrast, interference declined sharply on the integrated task over Days 1-3, then slowed to parallel the gradual decline on the separated task. Finally, training on the color naming task did not affect a word reading task administered after training. These findings imply that (a) Stroop interference initially reflects two problems—overcoming integration and managing two conflicting information sources; (b) with practice, the larger integration problem is solved relatively quickly, rendering the integrated and separated tasks quite comparable thereafter; and (c) facilitation and interference in the Stroop task may be independent. These results challenge extant theories of the Stroop effect, which do not predict such effects.     

Dilution of compatibility effects in Simon-type tasks depends on categorical similarity between distractors and diluters

The presence of a distracting stimulus during performance of the Stroop color-naming task leads to dilution of the Stroop effect. Because the automatic activation of word meaning may interfere with the task-relevant stimulus feature (text color; stimulus-stimulus [S-S] interference) and the response (saying the text color; stimulus-response [S-R] interference), it is unclear which of these types of interference is diluted. We introduce a new dilution paradigm using word- and arrow-based Simon tasks, in which only S-R interference is present. Participants made a left or right response to a central color target. A task-irrelevant location-word (Experiment 1) or arrow (Experiment 2) distractor adjacent to the target produced S-R compatibility effects. An additional neutral word or symbol series (diluter) was sometimes presented on the opposite side of the target from the distractor. The compatibility effect was smaller when the distractor and diluter category domains matched than when they mismatched. This result provides evidence that S-R compatibility effects are susceptible to the presence of diluters that are categorically similar to the distractors.     

The effects of amount of information in the Stroop color word test

The processing time of the relevant (color) and irrelevant (word) stimulus dimensions in a Stroop color word test were each varied by manipulating the amount of information in the color and word sets from which the stimuli were obtained. Interference in the Stroop task was found to increase with increases in relevant and irrelevant stimulus information. It was concluded that the findings of increased interference with increases in both word and color processing time supported a perceptual conflict interpretation of Stroop task interference.     

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.     

Stroop dilution depends on the nature of the color carrier but not on its location

Stroop dilution is the reduction of the Stroop effect in the presence of a neutral word. It has been attributed to competition for attention between the color word and neutral word, to competition between all stimuli in the visual field, and to perceptual interference. Five experiments tested these accounts. The critical manipulation was whether the color to be named was carried by the color word or the neutral word. Neutral words diluted the Stroop effect when they were the color carrier, but not when the color word was the color carrier. We argue that Stroop dilution is due to attentional competition between the color word and neutral word, with priority given to the color carrier.     

The reverse Stroop effect

In classic Stroop interference, manual or oral identification of sensory colors presented as incongruent color words is delayed relative to simple color naming. In the experiment reported here, this effect was shown to all but disappear when the response was simply to point to a matching patch of color. Conversely, strong reverse Stroop interference occurred with the pointing task. That is, when the sensory color of a color word was incongruent with that word, responses to color words were delayed by an average of 69 msec relative to a word presented in gray. Thus, incongruently colored words interfere strongly with pointing to a color patch named by the words, but little interference from incongruent color words is found when the goal is to match the color of the word. These results suggest that Stroop effects arise from response compatibility of irrelevant information rather than automatic processing or habit strength.     

Sustained suppression in congruency tasks

In a list version of the Stroop task, Thomas (1977) observed that Stroop interference was smaller when the irrelevant word was repeated through parts of the list. MacLeod (1991) formulated the sustained-suppression hypothesis for this effect. It is assumed that the automatic response activation on the basis of the irrelevant word is selectively suppressed. In this paper this hypothesis is further investigated. In a serial Stroop task with short response-stimulus interval (RSI) we demonstrate that the Stroop effect disappears when the irrelevant word is repeated, whereas the Stroop effect is evident when the word changes. With a long RSI, there is no influence of the sequence of the irrelevant word. The same pattern of results is observed in a flanker task. The results are discussed in terms of the activation-suppression model (Ridderinkhof, 2002) and the sustained-suppression hypothesis.     

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.     

Visual attention and word recognition in stroop color naming: is word recognition "automatic"?

In Stroop color naming, color targets were accompanied by a color word or a color word plus a neutral word that reduces or "dilutes" the Stroop effect. Abrupt-onset cues called the focus of attention to one stimulus or another. Cuing influenced the size of the Stroop effect but never eliminated it. Unlike the Stroop effect itself, Stroop dilution from the neutral word could be eliminated, by cuing the color word. Focusing visual attention on the color word protected it from Stroop dilution; focusing visual attention on the neutral word did not prevent Stroop interference. Thus, spatial attention is a modulator, protecting visual data from crosstalk, but a word need not be the focus of visual attention to be recognized.     

Integration versus separation in Stroop‐like counting interference tasks1

Abstract: Two versions of a Stroop‐like counting interference task were compared to examine how irrelevant information is ignored. In the integrated task, participants enumerated digits (inconsistent condition) or letters (neutral condition) while attempting to ignore the identity of the characters. In the newly created separated task, participants enumerated asterisks while attempting to ignore a single digit (inconsistent condition) or letter (neutral condition) at fixation. Interference (longer responses in the inconsistent condition than in the neutral condition) was small but significant in both tasks but was not reduced by separation. Contrasted with the pattern in the color–word Stroop task, these results suggest that dimensional separation has different effects on interference depending on the overall amount of interference.     

Relations between emotion,memory, and attention: Evidence from taboo Stroop,lexical decision,and immediate memory tasks

This article reports five experiments demonstrating theoretically coherent effects of emotion on memory and attention. Experiments 1-3 demonstrated three taboo Stroop effects that occur when people name the color of taboo words. One effect is longer color-naming times for taboo than for neutral words, an effect that diminishes with word repetition. The second effect is superior recall of taboo words in surprise memory tests following color naming. The third effect is better recognition memory for colors consistently associated with taboo words rather than with neutral words. None of these effects was due to retrieval factors, attentional disengagement processes, response inhibition, or strategic attention shifts. Experiments 4 and 5 demonstrated that taboo words impair immediate recall of the preceding and succeeding words in rapidly presented lists but do not impair lexical decision times. We argue that taboo words trigger specific emotional reactions that facilitate the binding of taboo word meaning to salient contextual aspects, such as occurrence in a task and font color in taboo Stroop tasks.     

Asymmetry of congruency effects in spatial Stroop tasks can be eliminated

Three experiments examined whether asymmetry in interference can be eliminated in spatial Stroop tasks. In Experiment 1, responding to arrows or location words written in Chinese and to their locations created spatial Stroop effects of similar sizes. In Experiment 2, responding to a location word embedded in an outline drawing of arrow did not yield a spatial Stroop effect, but responding to the arrow's direction did yield an effect. In Experiment 3, responding to a location word flanked by an arrow and to the arrow rather than the word produced similar sizes of spatial Stroop effects. These results show that asymmetry in spatial Stroop interference can be eliminated in some situations. Although aspects of the results are consistent with predictions of translation and dimensional overlap models, they are in closest agreement overall with an account in terms of the relative strengths of the relevant and irrelevant stimulus–response associations.     

The role of attentional slippage in Stroop dilution

The present study examined the cognitive locus of Stroop dilution using a psychological refractory period (PRP) paradigm. Participants were asked to perform a tone discrimination task via a bimanual keypress response and a modified Stroop task via a vocal response serially as Task 1 and Task 2, respectively. In Task 2, a neutral word was added on half of the trials and no neutral word on the other half of the trials to observe the Stroop dilution effect. The amount of Stroop dilution, as well as the Stroop effect, was relatively constant across different stimulus-onset asynchronies (SOAs), which implies that Stroop dilution occurs due to the competition between a neutral word and a color word after a target color bar is selected to be processed further. These results indicate that focused attention plays an important role in the modulation of Stroop interference by the presence of a neutral word.     

One night of sleep deprivation affects reaction time, but not interference or facilitation in a Stroop task

The Stroop color-naming task is one of the most widely studied tasks involving the inhibition of a prepotent response, regarded as an executive function. Several studies have examined performance on versions of the Stroop task under conditions of acute sleep deprivation. Though these studies revealed effects on Stroop performance, the results often do not differentiate between general effects of sleep deprivation on performance and effects specifically on interference in the Stroop task. To examine the effect of prolonged wakefulness on performance on the Stroop task, we studied participants in a 40-h "constant routine" protocol during which they remained awake in constant conditions and performed a Stroop color-naming task every two hours. We found that reaction time was slowest when the color and word did not match (incongruent), fastest when the color and word did match (congruent), and intermediate when participants named the color of the non-word stimulus (neutral). Performance on all three trial types degraded significantly as a function of time awake. Extended wakefulness did not significantly change the additional time needed to respond when the color and word did not match (Stroop interference), nor did it change the amount of facilitation when color and word matched. These results indicate that one night of sleep deprivation influences performance on the Stroop task by an overall increase in response time, but does not appear to impact the underlying processes of interference or facilitation. The results suggest that the degree to which an "executive function" is affected by sleep deprivation may depend on the particular executive function studied and the degree to which it is subserved by the prefrontal cortex.     

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。     

Stroop interference effects in partially colored Stroop words

In the Stroop task word reading is thought to be automatic since it runs without intentional monitoring and is difficult to avoid. This view has recently been challenged by observations that Stroop interference is reduced when only part of the Stroop word is colored. In this study we asked whether the extent of Stroop interference varies with the position of the colored letter(s). We observed that Stroop interference was smallest when the first letter(s) were colored and largest when either the last letter(s) or whole word were colored. On these findings we suggest that colored and noncolored parts of partially colored words are processed separately and differently, and that selection of the color dimension for explicit report entails inhibition of the to-be-ignored colored letters.     

Anxiety-Related Stroop Interference in Adolescents

A group of 16- to 18-year-old students was presented with threat-related and neutral Stroop stimuli on separate cards. Participants were assigned to anxiety groups on the basis of their scores on the Beck Anxiety Inventory (BAI; A. T. Beck & R. A. Steer, 1990). It was found, as predicted, that the high-anxiety group took significantly longer to identify the color of the threat-related word than the neutral words, whereas there was no difference for the low-anxiety group. There was a significant linear relationship between interference on the task and BAI scores, showing that as anxiety increases there is a corresponding increase in interference produced by the threat-related stimuli when compared with the neutral stimuli. This study demonstrates an anxiety-related Stroop interference effect for adolescents consistent with that reported in the adult literature.     

Anxiety-related Stroop interference in adolescents

A group of 16- to 18-year-old students was presented with threat-related and neutral Stroop stimuli on separate cards. Participants were assigned to anxiety groups on the basis of their scores on the Beck Anxiety Inventory (BAI; A. T. Beck & R. A. Steer, 1990). It was found, as predicted, that the high-anxiety group took significantly longer to identify the color of the threat-related word than the neutral words, whereas there was no difference for the low-anxiety group. There was a significant linear relationship between interference on the task and BAI scores, showing that as anxiety increases there is a corresponding increase in interference produced by the threat-related stimuli when compared with the neutral stimuli. This study demonstrates an anxiety-related Stroop interference effect for adolescents consistent with that reported in the adult literature.     

New data analysis of the stroop matching task calls for a reevaluation of theory

In Stroop matching tasks, participants indicate whether the color of an object matches the meaning of a color word printed in color. Previously in this journal, Luo (1999) concluded that interference between two incongruent representations of the same attribute (ink color) occurs prior to the response stage. However, this conclusion was based on questionable data analysis. We suggest analyzing the data by separating "same" and "different" responses and then analyzing three congruency conditions within the "different" responses: (a) congruence between word color and word meaning, (b) congruence between word color and object color, and (c) incongruence between word color, word meaning, and object color. In an experiment similar to Luo's, such an analysis revealed that responding was slowest in the first condition. This pattern of results does not fit with previous conclusions regarding this task, but rather indicates that task conflict and response competition contribute to interference. This analysis has implications for matching tasks other than the Stroop matching task.     

Investigating hemispheric specialization in a novel face-word Stroop task

We examined hemispheric specialization in a lateralized Stroop facial identification task. A 2 (presentation side: left or right visual field [LVF or RVF])x2 (picture emotion: happy or angry)x3 (emotion of distractor word: happy, angry, or blank) factorial design placed the right hemispheric specialization for emotional expression processing and the left hemispheric specialization for verbal processing in conflict. Faces (from ) and emotion words were briefly displayed, and participants responded with keypresses corresponding to the picture emotion. As predicted, greater Stroop interference in identification accuracy was found with incongruent displays of facial expression in the LVF and emotion words in the RVF, and females exhibited less Stroop interference. Reaction times were moderated by emotion and visual field.