Sequential congruency effects: disentangling priming and conflict adaptation

Responding to the color of a word is slower and less accurate if the word refers to a different color (incongruent condition) than if it refers to the same color (congruent condition). This phenomenon, known as the Stroop effect, is modulated by sequential effects: it is bigger when the current trial is preceded by a congruent condition than by an incongruent one in the previous trial. Whether this phenomenon is due to priming mechanisms or to cognitive control is still debated. To disentangle the contribution of priming with respect to conflict adaptation mechanisms in determining sequential effects, two experiments were designed here with a four-alternative forced choice (4-AFC) Stroop task: in the first one only trials with complete alternations of features were used, while in the second experiment all possible types of repetitions were presented. Both response times (RTs) and errors were evaluated. Conflict adaptation effects on RTs were limited to congruent trials and were exclusively due to priming: they disappeared in the priming-free experiment and, in the second experiment, they occurred in sequences with feature repetitions but not in complete alternation sequences. Error results, instead, support the presence of conflict adaptation effects in incongruent trials. In priming-free sequences (Experiment 1 and complete alternation sequences of Experiment 2) with incongruent previous trials there was no error Stroop effect, while this effect was significant with congruent previous trials. These results indicate that cognitive control may modulate performance above and beyond priming effects.     

Effects of Stroop task duration on subsequent cognitive and physical performance

The strength model of self-control purports to explain why brief cognitive response inhibition tasks impair subsequent isometric handgrip endurance. According to the model, ego depleting tasks requiring self-control resources impair performance on subsequent tasks that also require self-control resources. However, several lines of evidence challenge this model, including evidence of improved exercise performance following longer cognitive tasks. Our study investigated the effects of cognitive task duration on (1) subsequent physical endurance performance, (2) concurrent cognitive task performance, and (3) subsequent novel cognitive task performance. Adopting an experimental design, with Stroop task type (incongruent, congruent) and duration (5, 10, 20 min) as between-participant factors, participants (N = 180) completed a color word Stroop task, an isometric handgrip to exhaustion task, and a novel 5-min incongruent number word Stroop task. In the handgrip task, endurance performance was worse following incongruent word Stroop than congruent word Stroop for 10-min tasks but not 5-min and 20-min tasks. In the word Stroop task, accuracy was lower and speed was slower following incongruent word Stroop than congruent word Stroop. Importantly, reaction times improved with longer task durations. In the novel number Stroop task, accuracy was higher following incongruent word Stroop than congruent word Stroop. In conclusion, the finding that the ego depletion effect was moderated by cognitive task duration is better explained by the expected value of control model than the strength model.     

Item-specific control of automatic processes: Stroop process dissociations

The influence of word reading on Stroop color naming decreases as a function of the proportion of test items that are incongruent. This proportion-congruent effect is usually ascribed to strategies (e.g., maintaining task set) that operate at a general level to moderate the extent to which participants are influenced by word reading. However, in three experiments, effects at the level of specific items were found. Interference and facilitation were smaller for color names usually presented in an incongruent color than for color names usually presented in their congruent colors. This item-specific proportioncongruent manipulation affected the process dissociation (PD) estimate of the influence of word-reading processes but not that of color-naming processes. The results (1) indicate that item-specific, as opposed to general, mechanisms can reduce the influence of word-reading processes on Stroop performance and (2) demonstrate the PD procedure’s utility in studying Stroop phenomena.     

Conditional automaticity in subliminal morphosyntactic priming

We used a gender-classification task to test the principles of subliminal morphosyntactic priming. In Experiment 1, masked, subliminal feminine or masculine articles were used as primes. They preceded a visible target noun. Subliminal articles either had a morphosyntactically congruent or incongruent gender with the targets. In a gender-classification task of the target nouns, subliminal articles primed the responses: responses were faster in congruent than incongruent conditions (Experiment 1). In Experiment 2, we tested whether this congruence effect depended on gender relevance. In line with a relevance-dependence, the congruence effect only occurred in a gender-classification task but was absent in another categorical discrimination of the target nouns (Experiment 2). The congruence effect also depended on correct word order. It was diminished when nouns preceded articles (Experiment 3). Finally, the congruence effect was replicated with a larger set of targets but only for masculine targets (Experiment 4). Results are discussed in light of theories of subliminal priming in general and of subliminal syntactic priming in particular.     

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.     

Perception without awareness: further evidence from a Stroop priming task

In the present research, we examined the influence of prime-target stimulus onset asynchrony (SOA) on Stroop-priming effects from masked words. Participants indicated the color of a central target, which was preceded by a 33-msec prime word followed either immediately or after a variable delay by a pattern mask. The prime word was incongruent or congruent with the target color on 75% and 25% of the trials, respectively. The words followed by an immediate mask produced reliable Stroop interference at SOAs of 300 and 400 msec but not at SOAs of 500 and 700 msec. The words followed by a delayed mask produced a reversed (i.e., facilitatory) Stroop effect, which reached significance at an SOA of 400 msec or longer, but never at the shorter 300-msec SOA. Such an differential time course of both types of Stroop priming effects provides further evidence for the existence of qualitative differences between conscious and nonconscious perceptual processes.     

冲突控制是领域一般性的还是领域特殊性的?

本研究采用整合交叉范式整合了Stroop任务和Simon任务,在双重认知控制的框架下探讨冲突控制是领域一般性的还是领域特殊性的问题。结果发现:序列一致性效应只出现在任务内,不出现于任务间,显示对冲突的反应性控制具有领域特殊性;比例一致性效应不仅出现在同种任务中,而且扩展到不同任务中,显示对冲突的主动性控制具有领域一般性。本研究结果对于理解认知控制的本质和机制具有重要意义。     

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.     

Reversing the affective congruency effect: The role of target word frequency of occurrence

In this research the outcome of an affective priming experiment is shown to critically depend on the frequency of occurrence of the target words used. Low frequency target words (5.7 occurrences per million words) resulted in an affective congruency effect, i.e., faster responses following affectively congruent than incongruent primes. High frequency target words (32.6 occurrences per million) resulted in a reverse priming effect, i.e., faster responses following incongruent than congruent primes. The size of the congruency effect was larger than the size of the reverse priming effect, thus masking its emergence when word frequency was not taken into account. We propose that target word frequency has its influence via an accessibility-related mechanism having to do with differences in observed changes in affect between prime and target.     

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.     

Stroop effects on redemption and semantic effects on confession: simultaneous automatic activation of embedded and carrier words

The present study was aimed at assessing whether focusing attention on a task-relevant part of a word prevents processing of its meaning. Participants performed a color-naming task on a prime word followed by lexical decision on a probe. Primes were words, which could contain an embedded color word (e.g., “redemption”) written in an incongruent color. Probes were either semantically related (e.g., “confession”) or unrelated (e.g., “production”) to the prime word. A Stroop effect emerged for color words appearing either in the initial or in the final position of the carrier word. A priming effect also emerged, with faster responses to probes semantically related to the prime. These results are evidence that focusing attention on part of a prime (i.e., the embedded color word) does not prevent the semantic processing of the entire word.     

Priming outside of awareness and subsequent stimulus identification.

The influence of priming outside of awareness on performance of a color-recognition task was investigated. Using a tachistoscope, a color word that matched ("congruent prime") or did not match ("incongruent prime") the target color or a blank prime was followed by a pattern mask and the target color. Identification performance was superior on the blank prime trials to the congruent prime trials, with performance on the incongruent prime trials being the lowest. A subsequent study included a meaningless (XXX) prime condition, and it was found that meaningless primes interfered with target-color identification more than the congruent and blank prime conditions, but less than the incongruent prime condition, suggesting that primes, in addition to producing semantic activation, impose demands on information-processing capacity of the perceptual system.     

The crucial roles of stimulus matching and stimulus identity in negative priming

Negative priming refers to the situation in which an ignored item on an initial prime trial suffers slowed responding when it becomes the target item on a subsequent probe trial. In this experiment (and a replication), we demonstrate two ways in which stimulus consistency (matching) governs negative priming. First, negative priming for identical words occurred only when the prime distractor changed color when it became the probe target (i.e., constant cue to read the red word); negative priming disappeared when the prime distractor retained its color as the probe target (i.e., cue switches from read the red prime word to read the white probe word). Second, negative priming occurred for identical words, but not for semantically related words, whether related categorically or associatively. This pattern of results is consistent with a memory retrieval account, but not with an inhibition account of negative priming, and casts doubt on whether there is semantic negative priming for words.     

Multiple levels of control in the Stroop task

Multiple levels of control may be used in service of reducing Stroop interference. One is list-wide, whereby interference is reduced strategically in lists that include disproportionately more incongruent trials. A second, item-specific control is observed when proportion congruence is manipulated at the level of items. Item-specific control reduces interference for mostly incongruent relative to mostly congruent items. First, we show that item-specific control may drive both list-wide and item-specific proportion congruence effects (Experiment 1). We then show that item-specific control affects Stroop interference similarly when a single feature (a word) as opposed to a feature combination (a word 1 font type) signals proportion congruence (Experiment 2). Although this suggests that font type offers little advantage for controlling Stroop interference beyond the word, a novel, font-specific proportion congruence effect is observed in Experiment 3, indicating that font type can be used to control interference. These findings support the idea that multiple levels of control are used in reducing Stroop interference.     

The interactive effects of listwide control, item-based control, and working memory capacity on Stroop performance

Hypothesized top-down and bottom-up mechanisms of control within conflict-rich environments were examined by presenting participants with a Stroop task in which specific words were usually presented in either congruent or incongruent colors. Incongruent colors were either frequently (high contingency) or infrequently (low contingency) paired with the word. These items were embedded within lists consisting of either 100% congruent or 100% incongruent filler items to create mostly congruent or mostly incongruent lists. Results indicated a significant item-specific congruency effect, which was largest for high contingency responses and within mostly congruent lists. In addition, a significant listwide congruency effect was obtained, and this interacted with working memory capacity (WMC). There were larger listwide congruency effects for low WMC individuals. Finally, the pattern of Stroop interference across lists for low WMC individuals was dependent upon the congruency of the preceding trial. These results support multiple forms of cognitive control, as well as contingency learning, as mechanisms underlying proportion congruence effects in Stroop and other conflict tasks. These findings are interpreted within Braver, Gray, and Burgess's (2007) dual mechanisms of control theory.     

Depth of facial expression processing depends on stimulus visibility: Behavioral and electrophysiological evidence of priming effects

Participants performed a priming task during which emotional faces served as prime stimuli and emotional words served as targets. Prime-target pairs were congruent or incongruent, and two levels of prime visibility were obtained by varying the duration of the masked primes. To probe a neural signature of the impact of the masked primes, lateralized readiness potentials (LRPs) were recorded over motor cortex. In the high-visibility condition, responses to word targets were faster when the prime-target pairs were congruent than when they were incongruent, providing evidence of priming effects. In line with the behavioral results, the electrophysiological data showed that high-visibility face primes resulted in LRP differences between congruent and incongruent trials, suggesting that prime stimuli initiated motor preparation. Contrary to the above pattern, no evidence for reaction time or LRP differences was observed in the low-visibility condition, revealing that the depth of facial expression processing is dependent on stimulus visibility.     

Long-term semantic memory versus contextual memory in unconscious number processing

Subjects classified visible 2-digit numbers as larger or smaller than 55. Target numbers were preceded by masked 2-digit primes that were either congruent (same relation to 55) or incongruent. Experiments 1 and 2 showed prime congruency effects for stimuli never included in the set of classified visible targets, indicating subliminal priming based on long-term semantic memory. Experiments 2 and 3 went further to demonstrate paradoxical unconscious priming effects resulting from task context. For example, after repeated practice classifying 73 as larger than 55, the novel masked prime 37 paradoxically facilitated the "larger" response. In these experiments task context could induce subjects to unconsciously process only the leftmost masked prime digit, only the rightmost digit, or both independently. Across 3 experiments, subliminal priming was governed by both task context and long-term semantic memory.     

冲突观察能诱发冲突适应

重复启动效应和一致试次所占的比例都会影响冲突适应效应。采用词-色Stroop任务, 本研究在控制了重复启动效应和一致试次的比例之后, 通过三个实验共同探讨反应执行和冲突观察对冲突适应效应的影响。实验一发现当前试次的Stroop干扰效应, 但没有得到冲突适应效应; 在实验二中, 先前试次为四选一的选择反应时任务, 当前试次为词-色Stroop任务, 得到反转的冲突适应效应; 实验三和实验一程序相似, 但在先前试次上不执行反应, 得到了稳定的冲突适应效应。这些结果证明, 冲突观察能够诱发冲突适应机制, 提升当前的操作表现。     

A Stroop effect for spatial orientation

The author investigated the conditions under which a congruent or incongruent orientation word affects processing of the orientation of visual objects. Participants named the orientation of a rectangle that partially occluded another rectangle. Congruent or incongruent orientation words appeared in the relevant object, in the irrelevant object, or in the background. There were two main results. First, congruent orientation words produced faster orientation-naming responses than incongruent orientation words. This finding constituted a new Stroop effect for spatial orientation. Second, only words in the relevant (i.e., attended) object produced Stroop effects, whereas words outside the relevant object had no significant effects. This object-dependent modulation of Stroop effects resembled previous findings with color-naming tasks, and hence indicated that these modulations are not restricted to a particular type of task. In summary, results suggested that object-based attention plays an important role in processing of irrelevant words.