Suggestion reduces the stroop effect

We examined the effects of suggestion on Stroop interference in highly suggestible individuals. Participants completed the Stroop task with and without a suggestion to perceive Stroop words as meaningless symbols. Half the participants were given this suggestion in hypnosis, and half were given the suggestion without the induction of hypnosis. Suggestion produced a significant reduction in Stroop inhibition, accounting for about 45% of the variance in Stroop responding, regardless of whether hypnosis had been induced. These findings indicate that suggestion can at least partially overcome the automaticity associated with the Stroop effect.     

Suggestion overrides the Stroop effect in highly hypnotizable individuals

Cognitive scientists distinguish between automatic and controlled mental processes. Automatic processes are either innately involuntary or become automatized through extensive practice. For example, reading words is a purportedly automatic process for proficient readers and the Stroop effect is consequently considered the "gold standard" of automated performance. Although the question of whether it is possible to regain control over an automatic process is mostly unasked, we provide compelling data showing that posthypnotic suggestion reduced and even removed Stroop interference in highly hypnotizable individuals. Drawing on a large sample of highly hypnotizable participants, we examined the effects of suggestion on Stroop performance both with and without a posthypnotic suggestion to perceive the input stream as meaningless symbols. We show that suggestion administered to highly hypnotizable persons significantly reduced Stroop interference and derailed a seemingly automatic process.     

The influence of mere social presence on Stroop interference: New evidence from the semantically-based Stroop task

Several studies have shown that mere social presence reduces Stroop interference but processes underlying such effect are still poorly understood. Given that the standard Stroop task used in those studies confounds semantic and response competition, it remains unclear whether Stroop words are processed normally (Sharma, Booth, Brown, & Huguet, 2010) or whether the processing of their semantic representations is altered (Huguet, Galvaing, Monteil, & Dumas, 1999, Exp. 1). The direct evidence from the semantically-based Stroop task (i.e., a task that is free of response competition and thus isolates the semantic component of the Stroop interference, Neely & Kahan, 2001) provided in this paper attests normal semantic processing. Such result refutes the idea that semantic activation can be prevented or controlled by social presence and thus adds to the growing body of evidence showing that semantic activation is indeed automatic. Also importantly, this paper offers an alternative explanation of past findings, which holds that social presence simply reduces the response competition that occurs in the standard Stroop task and sheds some light on the processes that underlie social-facilitating effects of mere presence in the Stroop task.     

Posthypnotic suggestion and the modulation of Stroop interference under cycloplegia

Recent data indicate that under a specific posthypnotic suggestion to circumvent reading, highly suggestible subjects successfully eliminated the Stroop interference effect. The present study examined whether an optical explanation (e.g., visual blurring or looking away) could account for this finding. Using cyclopentolate hydrochloride eye drops to pharmacologically prevent visual accommodation in all subjects, behavioral Stroop data were collected from six highly hypnotizables and six less suggestibles using an optical setup that guaranteed either sharply focused or blurred vision. The highly suggestibles performed the Stroop task when naturally vigilant, under posthypnotic suggestion not to read, and while visually blurred; the less suggestibles ran naturally vigilant, while looking away, and while visually blurred. Although visual accommodation was precluded for all subjects, posthypnotic suggestion effectively eliminated Stroop interference and was comparable to looking away in controls. These data strengthen the view that Stroop interference is neither robust nor inevitable and support the hypothesis that posthypnotic suggestion may exert a top-down influence on neural processing.     

Hypnotic control of attention in the Stroop task: a historical footnote

Raz, Shapiro, Fan, and Posner (2002) have recently provided a compelling demonstration of enhanced attentional control under post-hypnotic suggestion. Using the classic color-word interference paradigm, in which the task is to ignore a word and to name the color in which it is printed (e.g., RED in green, say "green"), they gave a post-hypnotic instruction to participants that they would be unable to read. This eliminated Stroop interference in high suggestibility participants but did not alter interference in low suggestibility participants. replicated this pattern and further demonstrated that it is not due to a visual strategy (such as blurring or looking at a different location). As a historical footnote, we describe a "case study" from 18 years ago in which we observed the same result using a hypnotic instruction to a single highly suggestible individual that he could not read. The elimination of Stroop interference has important implications for both the study of attention and the study of hypnosis.     

Dissociating stimulus-stimulus and response-response effects in the Stroop task.

The separate semantic and response competition interactions between colour and word processing in a manual Stroop task were evaluated by comparing three trial types. Identity trials are both semantically compatible and response compatible (e.g., BLUE in the colour blue), different response trials are both semantically incompatible and response incompatible (e.g., BLUE in the colour green, where blue and green have different response keys), and same response trials are semantically incompatible and response compatible (e.g., the word BLUE in the colour red, where blue and red have the same key press response). Ink colours were embedded in two different word types, colour words, and colour associates. The results using colour words replicated the findings of De Houwer (2003) and demonstrated both a semantic effect (a difference between same response trials and identity trials) and response competition (a difference between same response trials and different response trials). In contrast, the results using colour associates provided evidence for only a semantic effect. These findings support interpretations of the colour associate Stroop effect that attribute the effect to semantics, but challenge Klein's (1964) response competition account and Sharma and McKenna's (1998) claim that the effect of colour associates is dependent on verbal responding. The results confirm that the Stroop colour-word task appears to involve at least two mechanisms, a semantic mechanism and a response competition mechanism.     

Temporal constraints of the word blindness posthypnotic suggestion on Stroop task performance

The present work investigated possible temporal constraints on the posthypnotic word blindness suggestion effect. In a completely within-subjects and counterbalanced design 19 highly suggestible individuals performed the Stroop task both with and without a posthypnotic suggestion that they would be unable to read the word dimension of the Stroop stimulus, both when response-stimulus interval (RSI) was short (500 ms) or equivalent to previous studies (3500 ms). The suggestion reduced Stroop interference in the short RSI condition (54 vs. 6 ms) but not in the long RSI condition (52 vs. 56 ms), and did not affect Stroop facilitation. Our results suggest that response to the suggestion involves reactive top-down control processes that persist only if levels of activation can be maintained. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Inducing a Stroop Effect

We examine the conditions that lead to Stroop interference for a meaningless linguistic label. Tiffany's cognitive model of drug abuse implies that individuals will respond more slowly to drug‐related words compared to neutral words in an emotional Stroop task, because the former have many automatic associations (e.g. positive expectancies). To examine this proposal, we trained participants to associate a meaningless label with either one other word or several other words and examined the induced Stroop interference for these meaningless labels. In two experiments, and contrary to expectations from Tiffany's work, we observed greatest Stroop interference for the meaningless label with just one association. These results are discussed in terms of associative learning theory. Copyright © 2009 John Wiley & Sons, Ltd.     

Graded auditory Stroop effects generated by gender words

Two auditory Stroop experiments requiring identification of the speaker's sex were conducted. An auditory Stroop effect was expected, analogous to visual effects found in Stroop literature. In Exp. 1 the speaker's sex was identified faster when sex labels ("male" and "female") and words that imply a sex (e.g., father, grandmother) were congruent with the speaker's sex. In Exp. 2, an auditory semantic gradient was established in which words that were more meaningfully tied to a particular sex produced more Stroop interference. This auditory semantic gradient is analogous to effects found in the visual Stroop literature of a semantic gradient related to color.     

Differential effects of viewing positions on standard versus semantic Stroop interference

From their finding that the substantial magnitude of the Stroop interference that occurs when a participant’s initial fixation is directed at the optimal viewing position is eliminated when the initial fixation is directed at the end of a word, Perret and Ducrot (2010) concluded that initial fixation at the latter position likely prevents reading. In the present study, we further examined this interpretation. To this end, the two conflict dimensions (semantic vs. response) that were confounded in the original work were separated within a semantically based Stroop paradigm (Neely & Kahan, 2001) that was administered with vocal (instead of manual) responses. In line with past findings showing greater interference in the vocal task, the reported results indicated that standard Stroop interference was reduced, but not eliminated, thus making the initial interpretation in terms of reading suppression unlikely. This conclusion is further strengthened by the presence of isolated semantic interference, the magnitude of which remained significant and was unaffected by viewing position. In sum, these results show that initial fixation of the end of a word simply reduces (nonsemantic) response competition.     

Locus of semantic interference in picture-word interference tasks

Picture#x2014;word interference studies typically show that semantically related distractor words embedded within a picture slow picture-naming responses, relative to unrelated ones. This semantic interference effect is commonly interpreted as arising from the competition of lexical#x2014;semantic (e.g., Schriefers, Meyer, & Levelt, 1990) or lexical#x2014;phonological (e.g., Starreveld & La Heij, 1996) codes. The experiment reported here tests a crucial assumption shared by these accounts#x2014;namely, that the effect reflects a lexical, rather than a nonverbal, conceptual conflict. Pictures were named while participants attempted to ignore embedded distractors that were in either verbal or pictorial format. The presence of both words and pictures substantially interfered with naming responses, but only words, not pictures, were found to induce semantic interference. These findings support the claim that for semantic interference to arise, both target picture and distractor have to be lexicalized. Consequently, a general conceptual locus of the effect can be excluded, and the claim that semantic interference is based on a lexical conflict is confirmed.     

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.     

The role of phonological activation in the visual semantic retrieval of Chinese characters

The Stroop paradigm was used to examine the role of phonological activation in semantic access and its development in reading Chinese characters. Subjects (age 7-23 years) of different reading ability were asked to name the display color of Chinese characters. The characters were displayed in four different colors: red, yellow, blue and green. There were five types of relationships between a character and its display color: semantically congruent, phonologically congruent, semantically incongruent, phonologically incongruent and neutral. In addition to the classical Stroop effects, interference and facilitation effects from the homophones of color characters were also observed. The younger children and those with lower reading ability exhibited stronger Stroop effects. These findings suggest that phonological codes are activated automatically in Chinese character recognition. Furthermore, there is more phonological activation in the semantic retrieval of children in lower grades and those with lower reading ability.     

Semantic processing of previews within compound words

Previous studies have suggested that previews of words prior to fixation can be processed orthographically, but not semantically, during reading of sentences (K. Rayner, D. A. Balota, & A. Pollatsek, 1986). The present study tested whether semantic processing of previews can occur within words. The preview of the second constituent of 2-constituent Finnish compound nouns was manipulated. The previews were either identical to the 2nd constituent or they were incorrect in the form of a semantically related word, a semantically unrelated word, or a semantically meaningless nonword. The results indicate that previews of 2nd constituents within compound words can be semantically processed. The results have important implications for understanding the nature of preview and compound word processing. These issues are crucial to developing comprehensive models of eye-movement control and word recognition during reading.     

Semantic component of a cross-modal Stroop-like task

Three experiments showed that the pattern of interference of single-modality Stroop tests also exists cross-modally. Distractors and targets were either pictures or auditory words. In a naming task (Experiment 1), word distractors from the same semantic category as picture targets interfered with picture naming more than did semantically unrelated distractors; the semantic category of picture distractors did not differentially affect word naming. In a categorization task (Experiment 2), this Stroop-like effect was reversed: Picture distractors from the same semantic category as word targets interfered less with word categorization than picture distractors that were semantically unrelated; the semantic category of word distractors did not differentially affect picture categorization. Experiment 3 replicated these effects when each subject performed both tasks; the task, naming or categorizing, determined the pattern of interference between pictures and auditory words. The results thus support the existence of a semantic component of a cross-modal Stroop-like effect.     

Is visual lexical access based on phonological codes? Evidence from a picture-word interference task

The claim that lexical access for visual words is mandatorily mediated by their phonological codes was investigated. Ninety-six subjects performed timed naming responses to pictures while instructed to ignore printed words superimposed on the pictures. Distractor words were either semantically related to the picture label or were homophones of a word semantically related to the picture name. On the basis of the claim that homophones initially activate multiple semantic codes, we hypothesized that the homophone and semantic distractors would yield comparable interference. Picture-word stimulus onset asynchrony (SOA) was varied between subjects as 0 or +100 msec. For an SOA of 0 msec, semantic interference, but no effect from the homophones, was obtained. For an SOA of +100 msec, no effect was obtained in either condition. In combination, these findings indicate a limited role of phonological codes in visual lexical access. It is suggested that the role of phonology in written word identification may vary dependent on procedure and utility to the task.     

Naming the color of a word: is it responses or task sets that compete?

Subjects named the colors in which high- and low-frequency words and pronounceable nonwords, otherwise matched, were displayed. Color naming was slower for all three item types than for visually equivalent strings of nonalphanumeric symbols but was no slower for words than for nonwords, nor for high-frequency words than for low-frequency words. Unpronounceable letter strings had intermediate color-naming latencies. However, frequency and lexical status had large effects on latency for reading the same words and pseudowords aloud. Interference is thus predicted not by the strength of association between a letter string and its pronunciation but by the presence of word-like constituents. We argue that the interference from an unprimed noncolor word is due to, and isolates, one of two components of the classic Stroop effect: competition from the whole task set of reading. The other component, response competition, occurs only when lexical access is sufficiently primed.     

The impact of semantic transparency of morphologically complex words on picture naming

We examined the contribution of semantic similarity to morphological priming effects, using the immediate (Exp. 1 and 3) and the delayed variant (Exp. 2) of picture-word interference. Distractor words were either compounds morphologically related to the picture name, but differing with respect to their semantic transparency (hummingbird, jailbird (Exp. 1); butterfly, butter dish (Exp. 3)), or form-related non-compound words (e.g., trombone). All three experiments revealed strong facilitation of picture naming due to morphologically related distractors. Form-related distractors facilitated picture naming in the immediate variant only, and to a lesser degree than compounds. Interestingly, the size of the morphemic effect was almost identical for semantically transparent and opaque complex words, which suggests that they share morphemic representations. These results suggest that morphological complexity in speech production is coded at the level of form representations, independent of semantic transparency.     

Reading aloud: The cumulative lexical interference effect

Picture naming shows a cumulative semantic interference effect: Latency for naming a target picture increases as a function of the number of pictures semantically similar to the target that have previously been named (Howard, Nickels, Coltheart, & Cole-Virtue, Cognition 100:464-482, 2006). Howard and colleagues, and also Oppenheim, Dell, and Schwartz (Cognition 114:227-252, 2010), argued that this occurs because of the joint presence in the picture-naming system of three critical properties: shared activation, priming, and competition. They also discussed the possibility that whenever any cognitive system possesses these three properties, a cumulative similarity-based interference effect from repeated use of that cognitive system will occur. We investigated this possibility by looking for a cumulative lexical interference effect when the task is reading aloud: Will the latency of reading a target word aloud increase as a function of the number of words orthographically/phonologically similar to the target that have previously been read aloud? We found that this was so. This supports the general idea that cumulative similarity-based interference effects will arise whenever any cognitive system that possesses the three key properties of shared activation, priming, and competition is repeatedly used.     

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.