Object-based attentional selection can modulate the Stroop effect

The Stroop (1935) effect is the inability to ignore a color word when the task is to report the ink color of that word (i.e., to say "green" to the word RED in green ink). The present study investigated whether object-based processing contributes to the Stroop effect. According to this view, observers are unable to ignore irrelevant features of an attended object (Kahneman & Henik, 1981). In three experiments, participants had to name the color of one of two superimposed rectangles and to ignore words that appeared in the relevant object, in the irrelevant object, or in the background. The words were congruent, neutral, or incongruent with respect to the correct color response. Words in the irrelevant object and in the background produced significant Stroop effects, consistent with earlier findings. Importantly, however, words in the relevant object produced larger Stroop effects than did the other conditions, suggesting amplified processing of all the features of an attended object. Thus, object-based processing can modulate the Stroop effect.     

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.     

Presenting two color words on a single Stroop trial: evidence for joint influence,not capture

MacLeod and Hodder (1998) demonstrated that presenting two different incongruent color words in the same color on a single Stroop trial resulted in no more interference than did presenting the same incongruent color word twice, and concluded that the first word captured attention, blocking out the second. They also showed that, within a trial, neither stimulus onset asynchrony between the two items nor the presence/absence of a visible gap between the two items had any effect. We replicated all of their empirical findings. Then, by extending their design and factorially combining three types of items--incongruent words, congruent words, and control nonwords--within a trial, we demonstrated that both items within a trial do influence processing, with the contribution of the second greater than that of the first. These results are incompatible with a capture account and suggest instead that the word dimension continues to be monitored during the attempt to identify and produce the name of the color.     

A reach-to-touch investigation on the nature of reading in the Stroop task

In a Stroop task, participants can be presented with a color name printed in color and need to classify the print color while ignoring the word. The Stroop effect is typically calculated as the difference in mean response time (RT) between congruent (e.g., the word RED printed in red) and incongruent (GREEN in red) trials. Delta plots compare not just mean performance, but the entire RT distributions of congruent and incongruent conditions. However, both mean RT and delta plots have some limitations. Arm-reaching trajectories allow a more continuous measure for assessing the time course of the Stroop effect. We compared arm movements to congruent and incongruent stimuli in a standard Stroop task and a control task that encourages processing of each and every word. The Stroop effect emerged over time in the control task, but not in the standard Stroop, suggesting words may be processed differently in the two tasks.     

Cognitive control outside of conscious awareness

To test whether cognitive control can operate fully unconsciously on conflicts arising between two interfering subliminal stimuli, we designed a priming paradigm in which a subliminal reverse Color-Word Stroop item (a color word written on a congruent/incongruent color rectangle) preceded a supraliminal one in each trial. We found (a) a conflict adaptation effect, with a smaller reverse Stroop effect on the visible probe items after incongruent than after congruent subliminal prime items and (b) a negative priming effect, with longer reaction-times on incongruent visible probe items when the color word corresponded to the color of the rectangle in the preceding subliminal prime item than when it was not. These effects replicate the ones classically reported in studies using visible items and suggest that cognitive control was transferred from the subliminal prime to the visible probe items. Taken together, our results demonstrate that cognitive control can operate on conflicting subliminal information.     

Name and face matching in one or two visual fields: a test of models of hemispheric specialization

In two experiments a name and a face (each male or female) were simultaneously flashed to either the same or opposite visual fields (left or right), for matching congruent (same sex) or incongruent (opposite sex), to test the predictions of various models of hemispheric specialization. While overall best performance occurred with a face in the left visual field (LVF) and a name in the right visual field (RVF), and worst with the opposite configuration, the general pattern of results was incompatible with either a direct access model or an activational/attentional account. The results were, however, most compatible with the predictions of a semispecialized hemispheres account, whereby cerebral asymmetries are seen as relative rather than absolute, either hemisphere being capable of processing either kind of material (verbal or visuospatial), but to different levels of efficiency. However, despite the fact that the stimulus materials had previously been shown to produce stable and consistent lateral asymmetries in the predicted directions when presented in isolation, in the composite, integrative matching task the position of the name seemed to be the major determinant of the resultant asymmetries. It would seem therefore that when such stimuli are to be cross matched, either left hemisphere (language) processes somehow dominate right hemisphere (visuospatial) processing (though not in the way that would be predicted by a simple activational/attentional account) or the left hemisphere's greater capacity predominates.     

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.     

Hemispheric differences in semantic processing: Category matching is not the same as category membership

Two closely related semantic processing tasks were studied under identical procedural conditions in order to examine lateral visual field effects on reaction times. In Experiment 1, reaction times did not differ as a function of visual field when subjects decided whether a lateral word was a member of a foveally presented category word (category membership task). On the other hand, reaction times were faster for right than for left visual field stimulus presentations when subjects decided whether two words, one lateral and one foveal, belonged to the same category (category matching task), although this advantage did not occur immediately. In Experiment 2, the laterality effect in the category matching task was studied as a function of word familiarity. Two groups of subjects performed the matching task for two blocks of trials, one group receiving the same word list in each block and the other receiving different lists. No visual field differences in reaction times were observed for either group during the first block of trials, but a distinct right field advantage appeared for both during the second block. The data from these experiments suggest that category matching strategies rely upon structures or processes localized in the left hemisphere, although their influence is not immediate. Category membership strategies, on the other hand, do not depend upon such localized structures.     

Neural correlates of perceptual narrowing in cross‐species face‐voice matching

Integrating the multisensory features of talking faces is critical to learning and extracting coherent meaning from social signals. While we know much about the development of these capacities at the behavioral level, we know very little about the underlying neural processes. One prominent behavioral milestone of these capacities is the perceptual narrowing of face–voice matching, whereby young infants match faces and voices across species, but older infants do not. In the present study, we provide neurophysiological evidence for developmental decline in cross‐species face–voice matching. We measured event‐related brain potentials (ERPs) while 4‐ and 8‐month‐old infants watched and listened to congruent and incongruent audio‐visual presentations of monkey vocalizations and humans mimicking monkey vocalizations. The ERP results indicated that younger infants distinguished between the congruent and the incongruent faces and voices regardless of species, whereas in older infants, the sensitivity to multisensory congruency was limited to the human face and voice. Furthermore, with development, visual and frontal brain processes and their functional connectivity became more sensitive to the congruence of human faces and voices relative to monkey faces and voices. Our data show the neural correlates of perceptual narrowing in face–voice matching and support the notion that postnatal experience with species identity is associated with neural changes in multisensory processing ( Lewkowicz & Ghazanfar, 2009 ).     

Think the thought, walk the walk - social priming reduces the Stroop effect

In the Stroop task, participants name the color of the ink that a color word is written in and ignore the meaning of the word. Naming the color of an incongruent color word (e.g., RED printed in blue) is slower than naming the color of a congruent color word (e.g., RED printed in red). This robust effect is known as the Stroop effect and it suggests that the intentional instruction – “do not read the word” – has limited influence on one’s behavior, as word reading is being executed via an automatic path. Herein is examined the influence of a non-intentional instruction – “do not read the word” – on the Stroop effect. Social concept priming tends to trigger automatic behavior that is in line with the primed concept. Here participants were primed with the social concept “dyslexia” before performing the Stroop task. Because dyslectic people are perceived as having reading difficulties, the Stroop effect was reduced and even failed to reach significance after the dyslectic person priming. A similar effect was replicated in a further experiment, and overall it suggests that the human cognitive system has more success in decreasing the influence of another automatic process via an automatic path rather than via an intentional path.     

Is an ant larger than a lion?

In order to examine the influence exerted by an irrelevant semantic variable in a comparative judgment task, we employed a Stroop-like paradigm. The stimuli were pairs of animal names that were different in their physical and semantic sizes (e.g., ant lion). Participants were asked to judge which of the two words was larger either in physical or in semantic size. Size congruity effect (i.e., faster reaction times with congruent than with incongruent stimuli) appeared in both semantic and physical judgments. The semantic distance effect (i.e., large semantic distances are processed faster than smaller ones), appeared only when the semantic dimension was relevant to the task. The findings indicate that when a word (animal name) is presented, its meaning is accessed automatically. Part of this meaning (at least with our stimuli) relates to the size of the animal in real life. Processing of meaning of the size of the words is carried out in parallel with the extraction of the physical features of the presented stimuli.     

Rapid proportion comparison with spatial arrays of frequently used meaningful visual symbols

It has been shown that when two arrays of Arabic numerals were briefly presented, observers could accurately indicate which array contained the larger number of a target numeral. This study investigated whether this rapid proportion comparison can be extended to other meaningful symbols that share some of notable properties of Arabic numerals. We tested mainly several Japanese Kanji letters, each of which represents a meaning and can work as a word. Using physically identical stimulus sets that could be interpreted as different types of letters, Experiment 1 first confirmed the rapid proportion comparison with Arabic numerals for Japanese participants. Experiment 2 showed that the rapid proportion comparison can be extended to Kanji numerals. Experiment 3 successfully demonstrated that rapid proportion judgments can be found with non-quantitative Kanji letters that are used frequently. Experiment 4 further demonstrated the rapid proportion comparison with frequently used meaningful non-letter symbols (gender icons). The rapid processing cannot be attributed to fluent processing of familiar items, because it was not found with familiar phonograms (Japanese Kana letters). These findings suggest that the rapid proportion comparison can be commonly found with frequently used meaningful symbols, even though their meaning is not relevant to the task.     

Is phonological recoding under strategic control?

Two experiments are reported in which subjects were required to name the color in which letter strings were printed. In the first experiment, color-naming latencies were the same when the letter strings were pseudohomophones of color words (e.g., PINC) as when they were color names (e.g., PINK). Both these conditions produced slower responses than control strings matched with the pseudohomophones for visual similarity to the color word (e.g., PINN). Unlike the first experiment, the second included trials in which the ink color was congruent with the color to which the letter string was related. The results with incongruent stimuli paralleled those in the first experiment. With the congruent stimuli, however, responses were faster with color words than with either their pseudohomophones or control strings, which were equally slow. It is proposed that phonological recoding occurs relatively slowly but cannot be suppressed even when it harms performance.     

Comparing perception of Stroop stimuli in focused versus divided attention paradigms: Evidence for dramatic processing differences

A huge set of focused attention experiments show that when presented with color words printed in color, observers report the ink color faster if the carrier word is the name of the color rather than the name of an alternative color, the Stroop effect. There is also a large number (although not so numerous as the Stroop task) of so-called “redundant targets studies” that are based on divided attention instructions. These almost always indicate that observers report the presence of a visual target (‘redness’ in the stimulus) faster if there are two replications of the target (the word RED in red ink color) than if only one is present (RED in green or GREEN in red). The present set of four experiments employs the same stimuli and same participants in both designs. Evidence supports the traditional interference account of the Stroop effect, but also supports a non-interference parallel processing account of the word and the color in the divided attention task. Theorists are challenged to find a unifying model that parsimoniously explains both seemingly contradictory results.     

Computational Evidence That Frequency Trajectory Theory Does Not Oppose But Emerges From Age‐of‐Acquisition Theory

According to the age‐of‐acquisition hypothesis, words acquired early in life are processed faster and more accurately than words acquired later. Connectionist models have begun to explore the influence of the age/order of acquisition of items (and also their frequency of encounter). This study attempts to reconcile two different methodological and theoretical approaches (proposed by Lambon Ralph & Ehsan, 2006 and Zevin & Seidenberg, 2002 ) to age‐limited learning effects. The current simulations extend the findings reported by Zevin and Seidenberg (2002) that have shown that frequency trajectories (FTs) have limited and specific effects on word‐reading tasks. Using the methodological framework proposed by Lambon Ralph and Ehsan (2006) , which makes it possible to compare word‐reading and picture‐naming tasks in connectionist networks, we were able to show that FT has a considerable influence on age‐limited learning effects in a picture naming task. The findings show that when the input–output mappings are arbitrary (simulating picture naming tasks), the links formed by the network become entrenched as a result of early experience and that subsequent variations in frequency of exposure of the items have only a minor impact. In contrast, when the mappings between input‐output are quasi‐systematic or systematic (simulating word‐reading tasks), the training of new items was generalized and resulted in the suppression of age‐limited learning effects. At a theoretical level, we suggest that FT, which simultaneously takes account of time and the level of exposure across time, represents a more precise and modulated measure compared with the order of introduction of the items and may lead to innovative hypotheses in the field of age‐limited learning effects.     

Preparation time modulates pro-active control and enhances task conflict in task switching

Performance in the Stroop task reflects two conflicts—informational (between the incongruent word and ink color) and task (between relevant color naming and irrelevant word reading). Neuroimaging findings support the existence of task conflict in congruent trials. A behavioral indication for task conflict—Stroop reverse facilitation—was found in previous studies under low task-control conditions. Task switching also causes reduction in task control because the task set frequently changes. We hypothesized that it would be harder to efficiently manage task conflicts in switching situations and, specifically, as cue–target interval (CTI) decreases. This suggestion was examined in two experiments using a combined Stroop task-switching design. We found a large interference effect and reverse facilitation that decreased with elongation of CTI. Results imply that task switching reduces pro-active task control and thereby enhances the informational and the task conflicts. This calls for a revision of recent control models to include task conflict.     

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.     

Apparent shift in visual field preference after unilateral stroke

Patients with either a left- or a right-hemisphere stroke lesion scored higher in tasks of word-picture matching and of nonverbal shape matching when information was presented tachistoscopically (120 msec) to the visual field (VF) projecting to their undamaged hemisphere. Left-hemisphere stroke patients (n = 13) were dissociated from right-hemisphere stroke patients (n = 15) by low word recognition from memory and by low right VF but nearly normal left VF accuracy in word-picture matching or shape matching; the former appeared to rely upon processing of word meaning by the right hemisphere. In contrast, right-stroke patients had higher right than left VF scores in both tasks, and their discrimination of nonverbal shapes via the right VF was not different from that of controls (n = 15). Preferred processing by the VF projecting to the undamaged hemisphere appeared as a shift in perceptual asymmetry but may indicate, in support of a "direct access" model, that each hemisphere responds more or less efficiently to word and to nonverbal shape discriminations.     

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.     

The role of color diagnosticity in object recognition and representation

The role of color diagnosticity in object recognition and representation was assessed in three Experiments. In Experiment 1a, participants named pictured objects that were strongly associated with a particular color (e.g., pumpkin and orange). Stimuli were presented in a congruent color, incongruent color, or grayscale. Results indicated that congruent color facilitated naming time, incongruent color impeded naming time, and naming times for grayscale items were situated between the congruent and incongruent conditions. Experiment 1b replicated Experiment 1a using a verification task. Experiment 2 employed a picture rebus paradigm in which participants read sentences one word at a time that included pictures of color diagnostic objects (i.e., pictures were substituted for critical nouns). Results indicated that the “reading” times of these pictures mirrored the pattern found in Experiment 1. In Experiment 3, an attempt was made to override color diagnosticity using linguistic context (e.g., a pumpkin was described as painted green). Linguistic context did not override color diagnosticity. Collectively, the results demonstrate that color information is regularly utilized in object recognition and representation for highly color diagnostic items.