The literature on interference in the Stroop Color-Word Task, covering over 50 years and some 400 studies, is organized and reviewed. In so doing, a set of 18 reliable empirical finding is isolated that must be captured by any successful theory of the Stroop effect. Existing theoretical positions are summarized and evaluated in view of this critical evidence and the 2 major candidate theories ―relative speed of processing and automaticity of reading― are found to be wanting. It is concluded that recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more sucessful than are earlier theories attempting to locate a single bottleneck in attention

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Half a century of research on the Stroop effect: an integrative review.

Preparing words in speech production is normally a fast and accurate process. We generate them two or three per second in fluent conversation; and overtly naming a clear picture of an object can easily be initiated within 600 msec after picture onset. The underlying process, however, is exceedingly complex. The theory reviewed in this target article analyzes this process as staged and feed-forward. After a first stage of conceptual preparation, word generation proceeds through lexical selection, morphological and phonological encoding, phonetic encoding, and articulation itself. In addition, the speaker exerts some degree of output control, by monitoring of self-produced internal and overt speech. The core of the theory, ranging from lexical selection to the initiation of phonetic encoding, is captured in a computational model, called WEAVER++. Both the theory and the computational model have been developed in interaction with reaction time experiments, particularly in picture naming or related word production paradigms, with the aim of accounting for the real-time processing in normal word production. A comprehensive review of theory, model, and experiments is presented. The model can handle some of the main observations in the domain of speech errors (the major empirical domain for most other theories of lexical access), and the theory opens new ways of approaching the cerebral organization of speech production by way of high-temporal-resolution imaging.

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A theory of lexical access in speech production.

The aim of this paper is to develop a theoretical model and a set of terms for understanding and discussing how we recognize familiar faces, and the relationship between recognition and other aspects of face processing. It is suggested that there are seven distinct types of information that we derive from seen faces; these are labelled pictorial, structural, visually derived semantic, identity-specific semantic, name, expression and facial speech codes. A functional model is proposed in which structural encoding processes provide descriptions suitable for the analysis of facial speech, for analysis of expression and for face recognition units. Recognition of familiar faces involves a match between the products of structural encoding and previously stored structural codes describing the appearance of familiar faces, held in face recognition units. Identity-specific semantic codes are then accessed from person identity nodes, and subsequently name codes are retrieved. It is also proposed that the cognitive system plays an active role in deciding whether or not the initial match is sufficiently close to indicate true recognition or merely a ‘resemblance’; several factors are seen as influencing such decisions.

This functional model is used to draw together data from diverse sources including laboratory experiments, studies of everyday errors, and studies of patients with different types of cerebral injury. It is also used to clarify similarities and differences between processes responsible for object, word and face recognition.

Understanding face recognition

The generation of words in speech involves a number of processing stages. There is, first, a stage of conceptual preparation; this is followed by stages of lexical selection, phonological encoding, phonetic encoding and articulation. In addition, the speaker monitors the output and, if necessary, self-corrects. Major parts of the theory have been computer modelled. The paper concentrates on experimental reaction time evidence in support of the theory.

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A theory of lexical access in speech production

Attentional bias is a central feature of many cognitive theories of psychopathology. One of the most frequent methods of investigating such bias has been an emotional analog of the Stroop task. In this task, participants name the colors in which words are printed, and the words vary in their relevance to each theme of psychopathology. The authors review research showing that patients are often slower to name the color of a word associated with concerns relevant to their clinical condition. They address the causes and mechanisms underlying the phenomenon, focusing on J.D. Cohen, K. Dunbar, and J.L. McClelland's (1990) parallel distributed processing model.

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The Emotional Stroop Task and Psychopathology

Presents a series of 6 experiments in which Stroop-like effects were generated by modally pure color-color, picture-picture, and word-word stimuli instead of the usual modally mixed color-word or picture-word stimuli. Naming, reading, and categorization tasks were applied. The Stroop inhibition was preserved with these stimuli but unexpectedly showed a semantic gradient only in the naming and not in the reading task. Word categorizing was slower and more interference prone than picture categorizing. These and other results can be captured by a model with two main assumptions: (a) semantic memory and the lexicon are separate, and (b) words have privileged access to the lexicon, whereas pictures and colors have privileged access to the semantic network. Such a model is developed and put to an initial test.

Context effects in stroop-like word and picture processing.

If a word is printed inside the outline drawing of a concrete object, interference patterns as in Stroop research are obtained under the instruction to name the picture or to read the word. Smith and Magee (1980) have shown that these patterns change fundamentally if the naming or reading task is replaced by a categorizing task. Their results seem to corroborate the relative speed hypothesis, which explains Stroop-like interferences by faster processing of the distractor than the target. Two experiments are reported here in which the time course of picture-word interferences was analyzed by a systematically varied stimulus onset asynchrony (SOA) of the two stimulus components in the picture-naming, word-reading, picture-categorizing, and word-categorizing tasks. The results argue against the relative speed hypothesis and suggest a functional internal processing asymmetry between inhibition-immune recoding, effective in word reading and picture categorizing, and inhibition-susceptible recoding in picture naming and word categorizing.

The time course of picture-word interference

Dyer (1971) investigated the response competition hypothesis of the Stroop phenomenon by temporally separating the color and word components of single stimuli (incongruent, control, and congruent) This line of research was continued in a series of five experiments that generalized Dyer's study: (a) In addition to the color-naming task, a reading task was included; (b) the irrelevant stimulus component was presented before and after the relevant one; (c) the probabilities of congruent and incongruent stimuli were varied; (d) besides color-word/color stimuli, color-color and word-word stimuli were used; and (e) the functional discrimination (color naming or reading) was compared with a sequential discrimination task The data suggest the following temporal relations: (a) a slow facilitation due to response bias; (b) its inhibitory counterpart; and (c) a fast, strong inhibition with no facilitatory complement that seems to correspond to the usual Stroop conflict but that seems to occur earlier than the response execution stage

Time course analysis of the Stroop phenomenon.

A new functional response competition model to describe the cognitive processes underlying the Stroop phenomenon is proposed. The main challenge for any explanation is the asymmetry of the conflict, i.e. the fact that the meaning of the color word disturbs naming the color of an incongruent color-word-color stimulus far more than the irrelevant color disturbs reading the word. The model proposes that the organism processes both competing verbal responses by priming the relevant set and inhibiting the irrelevant set if both responses belong to different sets, and by computing internal delay-time differences if both responses belong to the same set. The model explains most of the existing data about the Stroop phenomenon and is in full accordance with present knowledge on selective attention, stimulus encoding, response selection, and psychological refractory period. It is confirmed by data of a Stroop experiment using a set of verbal color responses disjoint from the set of the stimulus color words. This experiment is based on the strategy often used in Stroop research to try to obtain a reversed Stroop effect in order to find an explanation of the Stroop effect. The data show full symmetry of competition, that is a Stroop effect and a reversed Stroop effect of about the same amount of increased reaction time.

A functional model to localize the conflict underlying the stroop phenomenon

Experimental research of the recent decade with chronometric methods has shown that the Stroop interference is far more than only a failure of selective attention. The degree of the interference effects is a very sensitive indicator of internal knowledge structures and the processes that operate on them during elementary naming, categorizing, and comparison tasks. Glaser and Glaser (1989) presented a model to integrate the essential results of Stroop research so far. It contains four essential features. (1) There is a marked functional gap between the semantic memory and the mental lexicon. (2) The semantic memory contains the world knowledge of an individual, the lexicon contains his or her complete linguistic knowledge without semantic capabilities. These systems are specialized for the input and output functions of non-linguistic or linguistic knowledge, respectively. (3) The instruction rule states that in Stroop-like tasks there is a strong, involuntary tendency to process the distractor according to the instruction concerning the target. (4) The dominance rule predicts maximal interference if the perception of a verbal or nonverbal object provides a suitable, but wrong alternative to an internally computed code. In the present experiment, the concept-attribute interference was investigated in order to enlarge the empirical base of this model. The subjects were instructed to name colors as typical attributes of everyday objects that were presented as pictures or as words. In another condition, they had to name typical objects for pictorially or verbally given colors. The results showed a graded pattern of interference effects which is quite consistent with the Glaser and Glaser (1989) model.

Wilhelm R. Glaser

Papers

Context effects in stroop-like word and picture processing.

The time course of picture-word interference

Time course analysis of the Stroop phenomenon.

A functional model to localize the conflict underlying the stroop phenomenon

Chapter 1 Colors as Properties: Stroop-Like Effects between Objects and their Colors