On a variant of Stroop’s paradigm: Which cognitions press your buttons?

The Stroop effect typically refers to the fact that the time to identify the color of a visually presented word is affected by the relationship between the word and the color When the (irrelevant) word is semantically related to the color (e.g., the word green, presented in red) response time is slower than if the word is neutral or unrelated. One question that has been posed concerns whether semantics plays a role only when the task requires an explicit verbal response, or whether it also plays a role when the response is manual. Sharma and McKenna (1998) have reported that semantics plays a role only when the response is vocal. A reanalysis of their data shows that semantics also plays a role when manual responses are made.     

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.     

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.     

The Effects of Procedural Variations on Lateralized Stroop Effects

Several issues in the classic Stroop effect remain open, including (i) the stage of processing which gives rise to the effect, (ii) the effect of some procedural manipulations, (iii) the effect of hemispheric specialization and of interhemispheric interactions, and (iv) the existence of individual differences. In this paper, we investigate these issues using a series of experiments with central, lateral, and bilateral presentations of the Stroop stimuli. A total of 146 right-handed subjects took part in a multiexperiment study with relatively equal numbers of the two sexes participating in each experiment. We found that manual responses diluted but did not abolish the Stroop interference relative to vocal responses, arguing for a late processing stage account of the effect. However, separating the color patch from the color word either unilaterally or bilaterally did not significantly change the magnitude of the Stroop interference, arguing against a cost of interhemispheric transfer in the Stroop effect in normal subjects. We did, however, find evidence for hemispheric specialization in Stroop interference, greater in the left hemisphere than in the right hemisphere. Color words in the RVF produced the greatest Stroop effects regardless of the location of the color patch. In most cases, this laterality effect interacted with the sex of the subject, such that only males and a subgroup of females (i.e., those tested during a low estrogen phase in the menstrual cycle) showed evidence for greater Stroop effects when a color word projected to the left hemisphere than when it projected to the right hemisphere, regardless of the placement of the color patch.     

Attention and gaze shifting in dual-task and go/no-go performance with vocal responding

Evidence from go/no-go performance on the Eriksen flanker task with manual responding suggests that individuals gaze at stimuli just as long as needed to identify them (e.g., Sanders, 1998). In contrast, evidence from dual-task performance with vocal responding suggests that gaze shifts occur after response selection (e.g., Roelofs, 2008a). This difference in results may be due to the nature of the task situation (go/no-go vs. dual task) or the response modality (manual vs. vocal). We examined this by having participants vocally respond to congruent and incongruent flanker stimuli and shift gaze to left- or right-pointing arrows. The arrows required a manual response (dual task) or determined whether the vocal response to the flanker stimuli had to be given or not (go/no-go). Vocal response and gaze shift latencies were longer on incongruent than congruent trials in both dual-task and go/no-go performance. The flanker effect was also present in the manual response latencies in dual-task performance. Ex-Gaussian analyses revealed that the flanker effect on the gaze shifts consisted of a shift of the entire latency distribution. These results suggest that gaze shifts occur after response selection in both dual-task and go/no-go performance with vocal responding.     

Attention, spatial integration, and the tail of response time distributions in Stroop task performance

A few studies have examined selective attention in Stroop task performance through ex-Gaussian analyses of response time (RT) distributions. It has remained unclear whether the tail of the RT distribution in vocal responding reflects spatial integration of relevant and irrelevant attributes, as suggested by Spieler, Balota, and Faust (2000). Here, two colour-word Stroop experiments with vocal responding are reported in which the spatial relation between colour and word was manipulated. Participants named colours (e.g., green; say "green") while trying to ignore distractors that were incongruent or congruent words (e.g., red or green), or neutral series of Xs. The vocal RT was measured. Colour words in colour, white words superimposed onto colour rectangles (Experiment 1), and colour rectangles combined with auditory words (Experiment 2) yielded Stroop effects in both the leading edge and the tail of the RT distributions. These results indicate that spatial integration is not necessary for effects in the tail to occur in vocal responding. It is argued that the findings are compatible with an association of the tail effects with task conflict.     

Stroop dilution revisited: evidence for domain-specific, limited-capacity processing

Nine experiments show that in the context of Stroop dilution the extent to which flanking distractors are processed depends on the nature of the material at fixation. A Stroop effect is eliminated if a word or a nonword is colored and appears at fixation and the color word appears as a flanker. A Stroop effect is observed when the color carrier at fixation is from a different domain than the color word distractor (e.g., Arabic digits). It is argued that when the material at fixation is in the same domain as the color word distractor, the distractor is not processed. Taken together, these results implicate a role for material-specific, limited-capacity processing in the context of this variant of the Stroop paradigm.     

Orthographic and phonological activation in auditory and visual word recognition

A discrete-trials color naming (Stroop)’paradigm was used to examine activation along orthographic and phonological dimensions in visual and auditory word recognition. Subjects were presented a prime word, either auditorily or visually, followed 200 msec later by a target word printed in a color. The orthographic and phonological similarity of prime-target pairs varied. Color naming latencies were longer when the primes and targets were orthographically and/or phonologically similar than when they were unrelated. This result obtained for both prime presentation modes. The results suggest that word recognition entails activation of multiple codes and priming of orthographically and phonologically similar words.     

Differences in semantic encoding as a function of reading comprehension skill

Using a modified Stroop procedure, we examined the extent to which the semantic encoding of a word is governed by the context within which that word appears. Good and poor comprehenders named the color of target words following their reading of either sentences or single words representing the object nouns of the sentences. Target words represented contextually emphasized (appropriate) attributes of the object nouns, nonemphasized (inappropriate) attributes of these nouns, or object attributes not related to these nouns (neutral). For single-word contexts, all subjects exhibited equal semantic interference to appropriate and inappropriate targets, relative to neutral targets. For sentence contexts, however, good comprehenders exhibited semantic interference only to appropriate targets, whereas poor comprehenders again exhibited equal interference to appropriate and inappropriate targets. These findings suggest that differences in comprehension skill may be attributable, at least in part, to fundamental differences in the way in which sentences are semantically encoded.     

Differential components of the manual and vocal Stroop tasks

In this study, four components of the Stroop effect were examined for manual word and vocal responses. The components were lexical, semantic relatedness, semantic relevance, and response set membership. The results showed that all four components were present in the vocal response task. However, in the manual word response task, the only component that produced significant interference on its own was response set membership. These results do not support predictions made by recent translation models (see W. R. Glaser & M. O. Glaser [1989] and Sugg & McDonald [1994]). A possible solution was suggested that located two sites for Stroop interference. The lexical, semantic relatedness, and semantic relevance effects were located in the lexical system, whereas the response set membership effect was located at a response selection stage.     

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.     

RETRACTED ARTICLE: Losing control: Mostly incongruent lists postpone,but do not eliminate,the Stroop effect

Identifying the color (e.g., red) of a color word that is incongruent (e.g., “BLUE”) can be remarkably difficult. The Stroop effect is a measure of the interference between activity from word and color pathways. The efficacy of these pathways is thought to be highly contingent on the frequency of incongruent trials within a block. A block of trials with mostly incongruent (MI) trials typically results in a smaller Stroop effect than a block with mostly congruent (MC) trials. This reduction of the Stroop effect has been largely attributed to the strategic list-wide control of the word pathway. Here, the time course of the Stroop effect was explored using speed-accuracy tradeoff functions (SATfs) in tasks with 50 % congruent, MC, and MI trials. In the MC and 50 % congruent condition, color-word congruency affected the rate parameter of the SATf. In the MI condition, however, congruency affected the asymptote. This evidence is consistent with the idea that the strategic control of the word pathway is an effortful, temporary phenomenon, prone to buckle if responding is held in check.     

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.     

Modularity beyond perception: evidence from single task interference paradigms

We combine the Dimension-Action (DA) model with translational models to account for both the Stroop and the flanker effects. The basic assumption of the model is that there are distinct visual modules, each of which is endowed with both perception and response selection processes. We contrast this model with an alternative widespread view, the standard view, according to which the same response selection processes are shared by all tasks. The two views have different predictions concerning the flanker and Stroop tasks. Seven experiments test these predictions. The first five experiments show that there is a fundamental difference between the typical Stroop and flanker effects. Moreover, these experiments show that words denoting colors can affect print colors only when they are required for naming or when participants verbally mediate the print color task. Experiments 6 and 7 show that an analogous interaction between color and shape exists in the flanker task. These experiments as well as previous studies are consistent with the DA model and the modular view and pose serious difficulties for the standard view. Wider implications of a visual modular architecture are discussed as well.     

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.     

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.     

The importance of irrelevant-dimension variability in the stroop flanker task

Two experiments in which the Stroop flanker task was used were conducted in order to examine the influence of irrelevant dimension invariance on congruency effects. Participants responded manually to a central color patch flanked by a Stroop stimulus. In Experiment 1, invariance in flanker location was found to have no influence on word and color congruency effects. In contrast, invariance of flanker identity led to the disappearance of congruency effects. Experiment 2 indicated that the elimination of a congruency effect was restricted to the dimension that remained constant and did not influence the congruency effect of the other dimension that was presented at the same location. Results suggest that variance is a prerequisite to congruity effects, determining the activation of irrelevant dimensions.     

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.     

Social priming of dyslexia and reduction of the Stroop effect: What component of the Stroop effect is actually reduced?

Recently, Goldfarb, Aisenberg, and Henik (2011) showed that in a manual format of the Stroop task, dyslexia priming eliminates the normal magnitude of the interference-based Stroop-like findings otherwise exhibited by individuals participating in such research. Goldfarb et al. (2011) consequently concluded that the effect of word reading in a Stroop task (i.e., one automatic behavior) can be effectively controlled through an automatic instruction “do not read” (i.e., another automatic behavior). The present study further investigated these ideas by examining when and how dyslexia priming controls different processes involved in a Stroop task. To this end, the original finding was first replicated (Experiment 1) and subsequently extended to the vocal (instead of manual) response modality to examine whether previously reported eliminations of the Stroop effect persist with this response format (i.e., format producing larger Stroop effects). Since past work (e.g., Augustinova & Ferrand, 2012a; Brown, Joneleit et al., 2002; Ferrand & Augustinova, 2013) had suggested that various interventions were likely to reduce (rather than eliminate) the interference-based Stroop-like findings with vocal responses, a further aim of these experiments was to identify the component of these findings that dyslexia priming actually reduces. To this end, the effects of this intervention were examined in a more fine-grained variant of the Stroop task that distinguished between interference resulting from task-irrelevant processes involved in computing the lexical and semantic representations of the word (i.e., a written distractor to ignore) and task-relevant processes involved in the selection of a response (i.e., a color target to name) that are both involved in this task. In line with our past work (e.g., Augustinova & Ferrand, 2012a; Ferrand & Augustinova, 2013), the results of two experiments (Experiments 2 and 3) showed that in the vocal format, dyslexia priming reduces but does not eliminate the normal magnitude of the interference-based Stroop-like findings and that this reduction is solely due to the control of processes involved in the selection of a response (i.e., a color target to name) – processes that are known to be controllable in this format (Ferrand & Augustinova, 2013). Given that in this format, dyslexia priming had no effect on task-irrelevant processes involved in computing the lexical and semantic representations of a written distractor to be ignored – processes that are known to be automatic – further implications for the control of automatic processes via dyslexia priming are considered and an interpretation in terms of a unitary control mechanism for both the manual and vocal formats is proposed.     

Effect of conflicting cues on information processing: the 'Stroop effect' vs. the 'Simon effect'

This study examined the relationship between two sources of interference in human information processing: the Stroop effect and the Simon effect. Forty subjects pressed a left- or right-hand key in response to a Stroop color word located on the left or right side of a screen. For one group, ink color was the relevant cue and, for another group, word meaning was the relevant cue. Independent variables were: congruence, i.e., agreement or lack thereof between the ink color and meaning of the Stroop word; spatial correspondence, i.e., agreement or lack thereof between the location of the Stroop word and the location of the key used to make the response; and stimulus duration, i.e., 400 or 100 ms. Each of these variables had a significant effect on RT, and there were no significant interactions. According to Sternberg's additive-factor logic, these findings suggest that the Stroop effect (congruence) and the Simon effect (spatial correspondence) involve separate stages of processing. If one assumes that manipulation of stimulus duration effects the encoding stage, then results also suggest that neither the Stroop effect nor the Simon effect involves the stimulus encoding stage.