Working memory load but not multitasking eliminates the prepared reflex: further evidence from the adapted flanker paradigm

The prepared reflex (PR) metaphor (Exner, 1879; Woodworth, 1938) suggests that stimulus-response (S-R) instructions held in working memory (WM) can lead to autonomous response activation without any practice. Cohen-Kdoshay and Meiran (2007) showed flanker compatibility effects immediately following the instructions (First Trials Flanker Compatibility Effect, FTFCE) and also showed that FTFCE was eliminated when participants had to hold an additional novel task rule in mind. They attributed the elimination of the FTFCE to WM load, but did not rule out multitasking and associated increased control demands as a possible alternative explanation. In the present experiment, the authors compared a no-load condition, a load condition involving a secondary task that was changed in every block (thus requiring WM) and a multi-tasking condition involving a secondary that remained the same throughout the experiment. The results show FTFCE without load and in the multi-tasking condition but no FTFCE in the WM load condition, establishing the critical involvement of WM storage capacity in the FTFCE.     

The representation of instructions in working memory leads to autonomous response activation: Evidence from the first trials in the flanker paradigm

The authors examined whether instructions can lead to autonomous response activation even without practice. Eriksen and Eriksen's (1974) Eriksen, B. and Eriksen, C. 1974. Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception & Psychophysics, 16: 143–149. [Crossref], [Web of Science ®] , [Google Scholar] flanker compatibility paradigm was used to show that the flanker compatibility effect (FCE) is already present in the first trials following the stimulus–response instructions, before any of the stimuli have been repeated. This first-trials FCE was present even when participants were strongly motivated to ignore the flankers, and it disappeared under conditions of high working-memory (WM) load. The findings suggest that intention, formed by instructions, is involved in forming representations in WM that operate like a prepared reflex (Woodworth, 1938 Woodworth, R. S. 1938. Experimental psychology, New York: Holt, Rinehart and Winston.  [Google Scholar]). The implications of the finding to intentionality and frontal lobe functions are discussed.     

Flanker effects on motor output and the late-level response activation hypothesis.

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli, the flankers produce a flanker compatibility effect on behavioural measures. Current accounts of the flanker compatibility effect assume that both target and flanker stimuli affect response activation. This idea is supported by electrophysiological studies, which show that irrelevant flanker stimuli can affect the motor system. The present experiments examined the characteristics of flanker effects on the motor system by analysing the details of the motor output with response force measures. A total of 60 participants responded in the flanker task to arrows (Experiment 1) or letters (Experiment 2). Reaction time as well as response force increased on incompatible trials. Analyses of the distribution of incorrect activation revealed that both response times and correct motor output increased with the amount of incorrect activity. However, the flanker compatibility effect was only marginally modulated by incorrect activity. Results suggest that the largest part of the flanker compatibility effect cannot be attributed to response activation and competition at late levels of the response system.     

Hypnotic suggestion modulates cognitive conflict: the case of the flanker compatibility effect

The present work was aimed at investigating whether the flanker compatibility effect can be eliminated by means of a posthypnotic suggestion influencing attentional focusing. In Experiment 1, participants who scored high and low on hypnotic susceptibility performed the flanker compatibility task when naturally awake and when under a posthypnotic suggestion aimed at increasing the target's discriminability from the flankers. Results showed that the posthypnotic suggestion effectively eliminated the flanker compatibility effect in highly susceptible participants, whereas low-susceptibility participants did not show any reduction in the effect. In Experiment 2, highly susceptible participants performed the task after receiving a suggestion but without the induction of hypnosis. Results showed that the suggestion alone was not sufficient to reduce the flanker compatibility effect. These results support the view that in highly susceptible participants, hypnotic suggestion can influence the ability to focus on relevant information.     

When do irrelevant visual stimuli impair processing of identical targets?

Three experiments investigated whether the repeated-letter inferiority effect (RLIE) and repetition blindness (RB) are identical phenomena or not and how the RLIE can be reconciled with the flanker compatibility effect (FCE). Participants reported a masked target and ignored an unmasked distractor. We manipulated the type of distractor (identical, alternative target, or neutral), the order of presenting distractor and target, and the predictability of target location. When distractors preceded the targets, distractors identical to the target always caused deficits in target processing (i.e., RB). With simultaneous presentation, identical distractors caused deficits (i.e., an RLIE) for unpredictable target locations only. Yet the RLIE was significantly smaller than RB. This result suggests that simultaneously presented stimuli are identified serially, in random order, if target position is unpredictable. As a result, RB arises only in the 50% of all trials with identical distractors in which the distractor is identified before the target. With simultaneous presentation and predictable target location, however, parallel processing of targets and distractors was possible that gave rise to an FCE in recognition accuracy. Analyses of false alarm rates revealed no evidence of significant response biases.     

The joint flanker effect and the joint Simon effect: On the comparability of processes underlying joint compatibility effects

Previous studies observed compatibility effects in different interference paradigms such as the Simon and flanker task even when the task was distributed across two co-actors. In both Simon and flanker tasks, performance is improved in compatible trials relative to incompatible trials if one actor works on the task alone as well as if two co-actors share the task. These findings have been taken to indicate that actors automatically co-represent their co-actor’s task. However, recent research on the joint Simon and joint flanker effect suggests alternative non-social interpretations. To which degree both joint effects are driven by the same underlying processes is the question of the present study, and it was scrutinized by manipulating the visibility of the co-actor. While the joint Simon effect was not affected by the visibility of the co-actor, the joint flanker effect was reduced when participants did not see their co-actors but knew where the co-actors were seated. These findings provide further evidence for a spatial interpretation of the joint Simon effect. In contrast to recent claims, however, we propose a new explanation of the joint flanker effect that attributes the effect to an impairment in the focusing of spatial attention contingent on the visibility of the co-actor.     

Response-compatibility effects in children

The Eriksen Flanker task is a classic paradigm for investigating interference at the level of response compatibility. Several previous studies analyzed the ability of young children (starting at the age of four years) to ignore flanking distractors in children-specific variants of the task. However, in all published studies the interference took place at the perceptual level as well as on the level of response compatibility because the ‘compatible condition’ involved stimulus congruency as well as response compatibility. By confounding stimulus congruency and response compatibility, interference at the level of response programming and priming at the perceptual level cannot be distinguished: the observed flanker effects might not be the result of successfully ignoring but instead might just be explained due to priming. We tested 57 children aged between 7 and 12 years in a flanker variant in which all trials were perceptually incongruent but different at the level of response compatibility (compatible versus incompatible). Children showed a flanker effect (faster reaction times in response compatible trials) that was, however, in terms of the effect size, smaller than flanker effects reported in previous studies.     

The effects of alerting signals in action control: activation of S–R associations or inhibition of executive control processes?

Non-informative, task-irrelevant auditory alerting signals often lead to increased interference effects in selective attention paradigms (e.g., Simon, Eriksen flanker). Some authors conclude that the alerting attentional network, activated by the alerting signal, reveals an inhibitory influence upon the executive attentional network, resulting in attenuated executive control. Alternatively, in the present study we argue that increased interference effects might be explained by alerting signals facilitating response activation processes (i.e., the activation of established S–R links). In a modified Eriksen-flanker paradigm, we contrasted these assumptions. We used word flanker stimuli for which S–R associations were established and word flanker stimuli without S–R associations. The presence of an alerting signal increased flanker compatibility only for flanker stimuli for which S–R associations existed while flanker compatibility effects were the same for all flanker types in conditions without alerting signals. Therefore, we conclude that alerting signals enhance stimulus triggered visuo-motor response activation processes.     

The role of instructions,practice, and stimulus-hand correspondence on the Simon effect

Numerous studies of two-choice reaction tasks, including auditory and visual Simon tasks (i.e., tasks in which stimulus location is irrelevant) and visual compatibility tasks, have found that only spatial stimulus-response (S-R) correspondence affected S-R compatibility. Their results provided no indication that stimulus-hand correspondence was a significant factor. However, Wascher et al. (2001) suggested that hand coding plays a role in visual and auditory Simon tasks when the instructions are in terms of the finger/hand used for responding. The present experiments examined whether instructing subjects in terms of response locations or fingers/hands influenced the Simon effect for visual and auditory tasks. In Experiments 1-3, only spatial S-R correspondence contributed significantly to the Simon effect, even when the instructions were in terms of the fingers/hands. However, in Experiment 4, which used auditory stimuli and finger/hand instructions, the contribution of stimulus-hand correspondence increased with practice.     

Effects of speed and accuracy strategy on choice step execution in response to the flanker interference task

The purpose of this study is to examine the effects of a speed or accuracy strategy on response interference control during choice step execution. Eighteen healthy young participants were instructed to execute forward stepping on the side indicated by a central arrow (←, left vs. →, right) under task instructions that either emphasized speed or accuracy of response in the neutral condition. In the flanker condition, they were additionally required to ignore the 2 flanking arrows on each side (→→→→→, congruent or →→←→→, incongruent). Errors in the direction of the initial weight transfer (APA errors) and the step execution times were measured from the vertical force data. APA error was increased in response to the flanker task and step execution time was shortened with a speed strategy compared to an accuracy strategy. Furthermore, in response to the visual interference of the flanker task, speed instructions in particular increased APA errors more than other instructions. It may be important to manipulate the level of the speed-accuracy trade-off to improve efficiency and safety. Further research is needed to explore the effects of advancing age and disability on choice step reaction in a speed or accuracy strategy.     

Distance and ratio effects in the flanker task are due to different mechanisms

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli the flanking stimuli produce a compatibility effect, with increased response speed and accuracy on compatible as compared to incompatible trials. This flanker effect is larger when compatible trials are more frequent than incompatible trials (the ratio effect). A potential explanation of this ratio effect is that the occurrence of frequent incompatible trials causes the focus of spatial attention to be set narrower than when there are frequent compatible trials. The present investigation tests this hypothesis by comparing the flanker effect with near and far flankers. The hypothesis predicts that the flanker distance should modulate the ratio effect more when incompatible trials are frequent than when compatible trials are frequent. The results, however, show the opposite pattern: Distance effects are larger in conditions with frequent compatible trials. Moreover, the effect of distance but not the ratio effect was eliminated when flanker distance remained fixed across blocks of trials, and also when participants had to attend to flanker stimuli in a go-no-go task. These results suggest that the ratio effect does not result from an adjustment of the focus of spatial attention.     

Distance and ratio effects in the flanker task are due to different mechanisms

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli the flanking stimuli produce a compatibility effect, with increased response speed and accuracy on compatible as compared to incompatible trials. This flanker effect is larger when compatible trials are more frequent than incompatible trials (the ratio effect). A potential explanation of this ratio effect is that the occurrence of frequent incompatible trials causes the focus of spatial attention to be set narrower than when there are frequent compatible trials. The present investigation tests this hypothesis by comparing the flanker effect with near and far flankers. The hypothesis predicts that the flanker distance should modulate the ratio effect more when incompatible trials are frequent than when compatible trials are frequent. The results, however, show the opposite pattern: Distance effects are larger in conditions with frequent compatible trials. Moreover, the effect of distance but not the ratio effect was eliminated when flanker distance remained fixed across blocks of trials, and also when participants had to attend to flanker stimuli in a go–no-go task. These results suggest that the ratio effect does not result from an adjustment of the focus of spatial attention.     

Working memory and two-digit number processing

The processing of two-digit numbers in comparison tasks involves the activation and manipulation of magnitude information to decide which number is larger. The present study explored the role of different working memory (WM) components and skills in the processing of two-digit numbers by examining the unit-decade compatibility effect with Arabic digits and number words. In the study, the unit-decade compatibility effect and different WM components were evaluated. The results indicated that the unit-decade compatibility effect was associated to specific WM skills depending on the number format (Arabic digits and number words). We discussed the implications of these results for the decomposed view of two-digit numbers.     

The flanker compatibility effect as a function of visual angle, attentional focus, visual transients, and perceptual load: a search for boundary conditions

When subjects must respond to a relevant center letter and ignore irrelevant flanking letters, the identities of the flankers produce a response compatibility effect, indicating that they are processed semantically at least to some extent. Because this effect decreases as the separation between target and flankers increases, the effect appears to result from imperfect early selection (attenuation). In the present experiments, several features of the focused attention paradigm were examined, in order to determine whether they might produce the flanker compatibility effect by interfering with the operation of an early selective mechanism. Specifically, the effect might be produced because the paradigm requires subjects to (1) attend exclusively to stimuli within a very small visual angle, (2) maintain a long-term attentional focus on a constant display location, (3) focus attention on an empty display location, (4) exclude onset-transient flankers from semantic processing, or (5) ignore some of the few stimuli in an impoverished visual field. The results indicate that none of these task features is required for semantic processing of unattended stimuli to occur. In fact, visual angle is the only one of the task features that clearly has a strong influence on the size of the flanker compatibility effect. The invariance of the flanker compatibility effect across these conditions suggests that the mechanism for early selection rarely, if ever, completely excludes unattended stimuli from semantic analysis. In addition, it shows that selective mechanisms are relatively insensitive to several factors that might be expected to influence them, thereby supporting the view that spatial separation has a special status for visual selective attention.     

Working memory and two-digit number processing

The processing of two-digit numbers in comparison tasks involves the activation and manipulation of magnitude information to decide which number is larger. The present study explored the role of different working memory (WM) components and skills in the processing of two-digit numbers by examining the unit–decade compatibility effect with Arabic digits and number words. In the study, the unit–decade compatibility effect and different WM components were evaluated. The results indicated that the unit–decade compatibility effect was associated to specific WM skills depending on the number format (Arabic digits and number words). We discussed the implications of these results for the decomposed view of two-digit numbers.     

Examining the role of working memory resources in following spoken instructions

This study investigated the involvement of working memory (WM) in following spoken instructions using concurrent tasks designed to disrupt components of the Baddeley and Hitch WM model [Baddeley, A. D., & Hitch, G. J. (1974). Working memory. In G. H. Bower (Ed.), The psychology of learning and motivation: Advances in research and theory (Vol. 8, pp. 47–89). New York, NY: Academic Press]. In each of three experiments, participants were presented with sequences of instructions to be either verbally repeated or physically performed using relevant objects. Backward counting, articulatory suppression, and eye closure during instruction encoding all disrupted recall, and also impaired recall of the linkage between movements and objects. Recall of actions was more accurate when they were physically enacted than repeated verbally, an advantage that was not affected by concurrent tasks. These findings indicate that aspects of the recall of spoken instructions including the binding of constituent movements to objects draw on multiple WM resources. The benefits of physical enactment of the instructed sequence do not appear to depend on the components of WM investigated in these studies.     

Evaluative priming in a semantic flanker task: ERP evidence for a mutual facilitation explanation

In semantic flanker tasks, target categorization response times are affected by the semantic compatibility of the flanker and target. With positive and negative category exemplars, we investigated the influence of evaluative congruency (whether flanker and target share evaluative valence) on the flanker effect, using behavioral and electrophysiological measures. We hypothesized a moderation of the flanker effect by evaluative congruency on the basis of the assumption that evaluatively congruent concepts mutually facilitate each other’s activation (see Schmitz & Wentura in Journal of Experimental Psychology: Learning, Memory, and Cognition 38:984–1000, 2012). Applying an onset delay of 50 ms for the flanker, we aimed to decrease the facilitative effect of an evaluatively congruent flanker on target encoding and, at the same time, increase the facilitative effect of an evaluatively congruent target on flanker encoding. As a consequence of increased flanker activation in the case of evaluative congruency, we expected a semantically incompatible flanker to interfere with the target categorization to a larger extent (as compared with an evaluatively incongruent pairing). Confirming our hypotheses, the flanker effect significantly depended on evaluative congruency, in both mean response times and N2 mean amplitudes. Thus, the present study provided behavioral and electrophysiological evidence for the mutual facilitation of evaluatively congruent concepts. Implications for the representation of evaluative connotations of semantic concepts are discussed.     

Individual differences in conflict-monitoring: testing means and covariance hypothesis about the Simon and the Eriksen Flanker task

Conflict and context slow-down have been proposed as indicators of a conflict-monitoring system that initiates cognitive control to resolve conflicts in information processing. We investigated individual differences in conflict-monitoring and their associations with working memory (WM) and impulsivity. A total of 150 adults completed a Simon and an Eriksen flanker task, together with measures of WM and impulsivity. On both tasks, responses were slower and less accurate on incompatible than on compatible trials (conflict effect), and the conflict effect was larger when the preceding trial was compatible than when it was incompatible (context effect). Stimulus repetition did not explain the context effect. Individual differences could be attributed to three separable factors for each task: general speeded performance, conflict effect, and context effect. Evidence for across-task generality of these factors was sparse. Associations of these factors with impulsivity were weak at best. WM was correlated with general speed, and also with some but not all factors reflecting conflict-related processes.     

Modulation of focused attention by faces expressing emotion: evidence from flanker tasks

Three experiments evaluated whether facial expression can modulate the allocation of focused attention. Identification of emotionally expressive target faces was typically faster when they were flanked by identical (compatible) faces compared with when they were flanked by different (incompatible) faces. This flanker compatibility effect was significantly smaller when target faces expressed negative compared with positive emotion (see Experiment 1A); however, when the faces were altered to disrupt emotional expression, yet retain feature differences, equal flanker compatibility effects were observed (see Experiment 1B). The flanker-compatibility effect was also found to be smaller for negative target faces compared compatibility with neutral target faces, and for both negative and neutral target faces compared with positive target faces (see Experiment 2). These results suggest that the constriction of attention is influenced by facial expressions of emotion.     

The interaction between stop signal inhibition and distractor interference in the flanker and Stroop task

In the present study, two experiments were conducted to investigate the interaction between the behavioral inhibition, measured by the stop signal task, and distractor interference, measured by the flanker task and the Stroop task. In the first experiment, the stop signal task was combined with a flanker task. Analysis revealed that participants responded faster when the distractors were congruent to the target. Also, the data suggest that it is more difficult to suppress a reaction when the distractors were incongruent. Whether the incongruent distractor was part of the response set (i.e. the distractor could also be a target) or not, had no influence on stopping reactions. In the second experiment, the stop signal task was combined with a manual version of the Stroop task and the degree of compatibility was varied. Even though in the second experiment of the present study interference control is differently operationalized, similar results as in the first experiment were found, indicating that inhibition of motor responses is influenced by the presentation of distracting information that is not part of the response set.