Configuration-specific attentional modulation of flanker- -target lateral interactions

Elements of a contour are often easier to detect when they possess collinearity, with their local orientations matching the global orientation of the contour. We recently reported attentional modulation of such lateral interactions between a central near-threshold target Gabor patch and flanking high-contrast patches (Freeman et al, 2001 Nature Neuroscience 4 1032-1036). Here, we examined whether such attentional effects reflect specific modulation of mechanisms sensitive to collinear configurations, or instead more general modulation of sensitivity to either the global or local orientation-components of the stimulus. Thresholds for detecting a central Gabor target were measured, while observers also judged the Vernier alignment between one pair of flankers and ignored a second flanker pair (when present). Target contrast-thresholds were facilitated only when attending collinear flankers. There was no facilitation when attending flankers that shared only local orientation with the target, or flankers that fell on a global axis aligned with target orientation but having orthogonal local orientation. Ignored collinear flankers had no effect on target thresholds. These results demonstrate strong and specific attentional modulation of contour-integration mechanisms in early vision sensitive to collinear configurations.     

Attentional capture by emotional faces is contingent on attentional control settings

Attentional capture by schematic emotional faces was investigated in two experiments using the flanker task devised by Eriksen and Eriksen (1974). In Experiment 1, participants were presented with a central target (a schematic face that was either positive or negative) flanked by two identical distractors, one on either side (schematic faces that were positive, negative, or neutral). The objective was to identify the central target as quickly as possible. The impact of the flankers depended on their emotional expression. Consistent with a threat advantage hypothesis (negative faces are processed faster and attract more processing resources), responses to positive faces were slower when these were flanked by (response incompatible) negative faces as compared with positive or neutral faces, whereas responses to negative faces were unaffected by the identity of the flankers. Experiment 2 was a standard flanker task with letter stimuli except that the task-neutral flankers were schematic faces that were either positive, negative, or emotionally neutral. In this case, in which faces and emotional expressions were to be ignored, performance seemed entirely unaffected by the faces. This result suggests that attentional capture by emotional faces is contingent on attentional control settings.     

Attentional capture by emotional faces is contingent on attentional control settings

Attentional capture by schematic emotional faces was investigated in two experiments using the flanker task devised by Eriksen and Eriksen (1974). In Experiment 1, participants were presented with a central target (a schematic face that was either positive or negative) flanked by two identical distractors, one on either side (schematic faces that were positive, negative, or neutral). The objective was to identify the central target as quickly as possible. The impact of the flankers depended on their emotional expression. Consistent with a threat advantage hypothesis (negative faces are processed faster and attract more processing resources), responses to positive faces were slower when these were flanked by (response incompatible) negative faces as compared with positive or neutral faces, whereas responses to negative faces were unaffected by the identity of the flankers. Experiment 2 was a standard flanker task with letter stimuli except that the task-neutral flankers were schematic faces that were either positive, negative, or emotionally neutral. In this case, in which faces and emotional expressions were to be ignored, performance seemed entirely unaffected by the faces. This result suggests that attentional capture by emotional faces is contingent on attentional control settings.     

Perceptual load modulates attentional capture by abrupt onsets

The abrupt appearance of a new object captures attention, even when the object is task irrelevant. These findings suggest that abrupt onsets capture attention in a stimulus-driven manner and are not susceptible to top-down influences on attentional control. However, previous studies examining the ability of abrupt onsets to capture attention have used search displays that lacked significant complexity. Because attention is a limited capacity mechanism, it is possible that increasing the complexity, or perceptual load, of the search arrays may modulate capture by abrupt onsets. We used a flanker task to examine the effect of perceptual load on attentional capture by abruptly appearing objects. Subjects searched for a target letter through low-load (set size=1) and high-load (set size=6) displays. On each trial, irrelevant flankers also appeared, one as an onset and the other as an offset. Onset flankers affected search in low-load but not high-load displays. This modulation of attentional capture was not caused by generalized slowing when subjects searched through high-load displays; search for a single perceptually degraded target slowed response times but did not affect attentional capture. These findings demonstrate that attentional capture by an abrupt onset is attenuated when people search through high-load scenes.     

Attentional processing of “unattended” flankers: Evidence for a failure of selective attention

Results from research with the flanker task have been used to argue both that flankers are identified without attention and that flanker identificatin requires attention. In three experiments, we addressed this issue by examining flanker recall. In Experiment 1, we manipulated flanker redundancy, a variable that could influence attention to the flankers, in order to determine whether it affected the magnitude of the flanker effect, the magnitude of flanker recall, or both. Redundancy did not influence the flanker effect, and recall was high in both conditions, suggesting that the flankers were attended. The recall results contradicted those of Miller (1987), the only other study that we could find in which flanker recall was used. In Experiments 2 and 3, we examined differences between Miller’s procedure and ours. Although flanker recall was lower when open-ended rather than forced recall was used and when the flanker task was made more complicated, flanker recall remained well above chance in all conditions. The data strongly suggest that in the typical correlated flanker task there is a failure of selective attention at some point during processing such that flankers receive attentional processing.     

Flanker recall and the flanker validity effect may reflect different attentional processes

High flanker recall in the correlated flanker task suggests a failure of selective attention. We used a dissociation approach to examine the role of attentional processing of the flankers’ identities in the flanker validity effect (FVE). In three experiments, flanker recall decreased as flanker duration decreased, but the FVE was not affected by flanker duration. Masking also produced a dissociation, in that masking decreased flanker recall but the FVE was not affected. Examination of on-line flanker identification suggested that flanker recall was an adequate measure of attentional processing of the flankers’ identities on most trials. The results suggest that attentional processing of the flankers’ identities is not related to the magnitude of the FVE and is not necessary for it to obtain. Because there is a failure of selective attention, the dissociations suggest that flanker recall and the FVE may reflect different attentional processes.     

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.     

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.     

Object-based attention: sensory modulation or priority setting?

The detection of an invalidly cued target is faster when it appears within a cued object than when it appears in an uncued object equally distant from the cued location; this is a manifestation of object based attention. Five experiments are reported in which it was investigated whether early sensory enhancement (in which attention "spreads" within an attended object but stops at its borders) or a later attentional prioritization mechanism best accounts for these effects. In Experiments 1-4, subjects identified a centrally located target with a buttonpress while attempting to ignore flanking distractors that were mapped to either a compatible or an incompatible response. The flankers appeared either within the object occupied by the target or in a different object but at the same distance from the target. The well-known effect of distance between the target and the flankers on the magnitude of the compatibility effect was replicated. However, whether the target and the flankers were in the same or different objects had no effect on the magnitude of the compatibility effect. In Experiment 5, when attention could not be narrowly focused in advance, object-based modulation of the flanker effect was observed. These results suggest that object-based selection may reflect an object-specific attentional prioritization strategy, rather than object-based attentional modulation of an early sensory representation.     

Evidence for selective target processing with a low perceptual load flankers task

In this article, we demonstrate that selective target processing is possible when the perceptual load of the task is low. We presented a row of three items with two different identities: one identity for the target letter and one for the two flankers (B. A. Eriksen & C. W. Eriksen, 1974). Such stimulus arrays have been defined as low-load displays (Lavie & Tsal, 1994). We investigated whether subjects could ignore the irrelevant flankers, which were never response alternatives, by manipulating the predictive relationship between the flankers and the response (Miller, 1987). In a high-correlation block, the identity of the flankers was highly predictive of the target identity, whereas in a lowcorrelation block, the predictive value of the flankers was reduced. We varied (1) whether or not the target location was precued, (2) the flanker’s category (digit vs. letter), (3) the target-flanker proximity (near = 3° vs. far = 5°), and (4) the size of the characters. The results indicate that subjects were influenced by the predictive value of near flankers and that the magnitude of this effect was jointly modulated by the target-flanker categorical overlap and by the size of the characters. In contrast, null flanker effects were obtained for far letter flankers in the precue condition, and for far digit flankers, regardless of attentional cuing. These findings (1) are inconsistent with suggestions (Lavie, 1995) that irrelevant stimuli automatically capture attention, and (2) support the notion that target-flanker distinctiveness plays a role when the perceptual load of the task is low.     

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.     

Eliminating flanker effects and negative priming in the flankers task: evidence for early selection

Reports of negative priming in the absence of flanker effects (Fox, 1995) provide support for the notion that unattended stimuli are identified. I evaluated the hypothesis that such results are the outcome of attentional leakage to the flanker location. In Experiment 1, I assessed flanker effects and negative priming as a function of target-flanker proximity (.9 degrees and 2.7 degrees for near and far flankers, respectively) and of attention cuing to the target location (precued vs. uncued) on the prime trials. I report larger flanker effects in uncued than in precued conditions, and larger effects for near than for far flankers. More critically, when attention was precued, both flanker effects and negative priming vanished for far flankers. In Experiment 2, I show that the latter result was not linked to prime-probe contextual similarity (Neill, 1997). These results demonstrate that selective target processing is possible when attention is optimally focused to the target location.     

Attentional scanning in the selection of central targets from multi-symbol strings

Abstract

Subjects responded to five-symbol strings consisting of a central target, one or two compatible or incompatible flankers, and neutral symbols in the remaining positions. Performance strongly depended on the position of compatible or incompatible flankers. With normal letters, left-side flankers had a much larger impact than right-side flankers. This left-side asymmetry of the flanker compatibility effect disappeared with strings composed of spaced letters or of tiny pictures and tended to turn into a right-side asymmetry with vertically mirrored letters. These results seem to indicate the operation of attentional scanning processes. Flankers may be scanned either automatically, due to a reading-like habit, or strategically, in attempting to localize the target.     

Negative triangles: simple geometric shapes convey emotional valence

It has been suggested that downward pointing triangles convey negative valence, perhaps because they mimic an underlying primitive feature present in negative facial expressions (Larson, Aronoff, and Stearns, 2007). Here, we test this proposition using a flanker interference paradigm in which participants indicated the valence of a central face target, presented between two adjacent distracters. Experiment 1 showed that, compared with face flankers, downward pointing triangles had little influence on responses to face targets. However, in Experiment 2, when attentional competition was increased between target and flankers, downward pointing triangles slowed responses to positively valenced face targets, and speeded them to negatively valenced targets, consistent with valence-based flanker compatibility effects. These findings provide converging evidence that simple geometric shapes may convey emotional valence.     

Interactions between color and word processing in a flanker task

To examine interactions between color and word attributes, participants responded, either manually or vocally, to a central target (color patch or word) flanked by a Stroop stimulus. Color and word attributes of the flanker affected both vocal and manual responding to color patches. Color and word flankers also affected manual responding to word targets, but only word flanker affected vocal responding to word targets. These results are not consistent with models (e.g., translational models) of Stroop tasks, which posit that interactions between colors and words occur only when vocal responding is required.     

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.     

Who is more prone to distraction? A simple test to evaluate the interference of emotional stimuli in females and males / ¿Quién se distrae más? Un sencillo test para evaluar la interferencia de los estímulos emocionales en mujeres y hombres

Abstract

In order to quantify gender differences in attentional capability depending on the presence of emotional stimuli, the effectiveness of responses to a target stimulus were analysed between groups. Fifty-two men and 52 women carried out two experiments based on the Eriksen flanker task. Half the participants were instructed to indicate the orientation of an arrow without flankers. The other half carried out the same task, but in this case the arrow was flanked by images with sexual or relaxing content. The study suggests that men are faster than women in discriminating the spatial orientation of a relevant stimulus, despite being more prone to distraction by adjacent stimuli. Regarding emotional interference, which is equivalent in both genders, it is higher for images with sexual content compared to those with relaxing content.     

Strategies of flanker coprocessing in single and dual tasks

In this study, the authors used a dual-task flanker paradigm to investigate the degree to which flankers are coprocessed with the target as a function of whether flankers have to be used as stimuli for a second task. A series of experiments, in which performance in dual tasks was compared with that in single tasks, revealed that participants had a strong tendency to coprocess flankers to a large degree in dual tasks, even if this impaired performance. Coprocessing of flankers was reduced only when totally irrelevant flankers were presented at the beginning of a trial or single tasks were performed on the great majority of trials within a block. The results suggest that it was demanding to process targets and flankers serially when both had to be used for a dual task. As a consequence, target and flankers were processed in parallel, even if this was nonoptimal for target selection.     

Testing the attention shift hypothesis as an account for the flanker sequence-based congruency modulation in spatial flanker tasks

Smaller Simon effects when stimulus locations are repeated on successive trials rather than alternated have been explained by the attention shift hypothesis, suggesting that shifts of attention result in interfering response codes. We investigated whether the attention shift hypothesis can also explain smaller flanker effects for repeated flankers than for alternated flankers, which occur only with directional information. In 3 peripheral letter identification tasks, target locations were cued by partial or complete flanker stimuli. Experiments 1 and 2 showed that directional flankers elicit shifts of attention. However, Experiment 3 revealed that directional flankers induced inverted cuing effects when reacting to the central target arrow was additionally required. These results are difficult to reconcile with the attention shift hypothesis as an explanation for the congruency reduction with repetitions of directional flankers.     

Flanker and negative flanker effects in letter identification

In a speeded choice reaction time task, responses to centrally presented letter targets can be altered by the identity of surrounding task-irrelevant letters (flankers). In the standard flanker effect, flankers associated with the same response as the target lead to faster and more accurate responses, whereas flankers associated with a different response lead to slower and more error-prone responses. B. A. Eriksen and C. W. Eriksen (1974, pp. 143-149) have argued that these flanker effects occur through response competition. We present data from a novel version of the Eriksen task, in which some targets and flankers consist of letter forms that are morphed versions of target letters. In this paradigm, flankers induce classic flanker effects on well-formed targets. But flankers induce an opposite effect, termed a negative flanker effect on morphed letter targets. For example, targets that are morphs between the letters "A" and "H" are more likely to be identified as an "A" when flanked by an "H." The interpretation advanced here is that there are two distinct kinds of flanker effects contrast enhancement in perceptual processes and response competition in response selection processes.