Distractor-response bindings in dual task scenarios

If a response is executed in reaction to a target stimulus, accompanying distractor stimuli can be integrated with and later on retrieve this response, an effect called distractor-response binding. There has been some debate as to whether S-R binding is generally influenced by attentional processes and in particular the role of attentional processes for the binding of irrelevant stimuli and responses is unclear. We therefore analyze the impact of spatial input attention while engaging central attention in an additional task. In particular, participants worked in dual task situations that induced load on central attention while the distribution of spatial attention was manipulated by varying the location of the different tasks. Distractor-response binding occurred only if both tasks were presented in the same spatial location. In contrast, binding effects within one task were prevented if spatial attention was withdrawn from the task by presenting a second task in a separate area. It is concluded that input but no central attention is required for the integration of distractor stimuli and responses. Theoretical and practical implications of these findings are discussed.     

Extinction-like effects in normals: independence of localization and response selection

An extinction-like effect in normal subjects was previously elicited when a low-salience target in the left was simultaneously presented with a highly salient distractor in the right visual hemifield, but not vice versa (Pollmann, 1996). We investigated in four experiments whether this extinction-like effect depends on (a) explicit localization and (b) response competition. It was found that the extinction-like effect could be replicated in the absence of both. In contradistinction to our previous results, low-salience distractors had no effect on pop-out target search. This showed that explicit spatial localization demands lead to low-salience distractor interference on pop-out search.     

Made you blink! Contingent attentional capture produces a spatial blink

Previous studies have shown that the capture of attention by an irrelevant stimulus can be eliminated by fore knowledge of the spatial location of the relevant target stimulus. To explore whether spatial certainty is sufficient to eliminate capture, four experiments are reported in which the spatial location of the target is certain but the temporal position is uncertain. Subjects viewed a central rapid serial visual presentation stream in which a target letter was defined by a particular color (e.g., red). On critical trials, irrelevant color singletons appeared in the periphery. In Experiments 1 and 2, peripheral singletons produced a decrement in central target identification that was contingent on the match between the singleton color and the target color. Experiments 3 and 4 provided evidence that this decrement reflected a shift of spatial attention to the location of the distractor. The results suggest that spatial certainty is not sufficient to eliminate attentional capture and that attentional capture can result in a spatial "blink" that is conditional on top-down attentional control settings.     

Top-down and bottom-up attentional control: On the nature of interference from a salient distractor

In two experiments using spatial probes, we measured the temporal and spatial interactions between top-down control of attention and bottom-up interference from a salient distractor in visual search. The subjects searched for a square among circles, ignoring color. Probe response times showed that a color singleton distractor could draw attention to its location in the early stage of visual processing (before a 100-msec stimulus onset asynchrony [SOA]), but only when the color singleton distractor was located far from the target. Apparently the bottom-up activation of the singleton distractor’s location is affected early on by local interactions with nearby stimulus locations. Moreover, probe results showed that a singleton distractor did not receive attention after extended practice. These results suggest that top-down control of attention is possible at an early stage of visual processing. In the long-SOA condition (150-msec SOA), spatial attention selected the target location over distractor locations, and this tendency occurred with or without extended practice.     

Top-down and bottom-up attentional control: on the nature of interference from a salient distractor.

In two experiments using spatial probes, we measured the temporal and spatial interactions between top-down control of attention and bottom-up interference from a salient distractor in visual search. The subjects searched for a square among circles, ignoring color. Probe response times showed that a color singleton distractor could draw attention to its location in the early stage of visual processing (before a 100-msec stimulus onset asynchrony [SOA]), but only when the color singleton distractor was located far from the target. Apparently the bottom-up activation of the singleton distractor's location is affected early on by local interactions with nearby stimulus locations. Moreover, probe results showed that a singleton distractor did not receive attention after extended practice. These results suggest that top-down control of attention is possible at an early stage of visual processing. In the long-SOA condition (150-msec SOA), spatial attention selected the target location over distractor locations, and this tendency occurred with or without extended practice.     

An attentional-adaptation account of spatial negative priming: Evidence from event-related potentials

Negative priming (NP) refers to a slower response to a target stimulus if it has been previously ignored. To examine theoretical accounts of spatial NP, we recorded behavioral measures and event-related potentials (ERPs) in a target localization task. A target and distractor briefly appeared, and the participant pressed a key corresponding to the target’s location. The probability of the distractor appearing in each of four locations varied, whereas the target appeared with equal probabilities in all locations. We found that response times (RTs) were fastest when the prime distractor appeared in its most probable (frequent) location and when the prime target appeared in the location that never contained a distractor. Moreover, NP effects varied as a function of location: They were smallest when targets followed distractors in the frequent distractor location—a finding not predicted by episodic-retrieval or suppression accounts of NP. The ERP results showed that the P2, an ERP component associated with attentional orientation, was smaller in prime displays when the distractor appeared in its frequent location. Moreover, no differences were apparent between negative-prime and control trials in the N2, which is associated with suppression processes, nor in the P3, which is associated with episodic retrieval processes. These results indicate that the spatial NP effect is caused by both short- and long-term adaptation in preferences based on the history of inspecting unsuccessful locations. This article is dedicated to the memory of Edward E. Smith, and we indicate how this study was inspired by his research career.     

Perceptual load modulates the processing of distractors presented at task-irrelevant locations during the attentional blink

The distribution of attention in both space and time is critical for processing our dynamic environment. Studies of spatial attention suggest that the distribution of attention is decreased when the perceptual load of a task increases, resulting in decreased processing of task-irrelevant distractors. Studies of the attentional blink (AB) suggest that the temporal distribution of attention also influences distractor processing, such that distractor processing increases during the AB relative to outside the AB (Jiang & Chun, 2001). Two experiments are reported in which the extent to which the difficulty of the first target task (T1) modulates the processing of task-irrelevant distractors during the AB was tested. To investigate this issue, both the first and second target tasks (T1 and T2) required identifying a central stimulus that was flanked by low-load or high-load distractors. Consistent with previous studies of the AB, there was evidence of more distractor processing during the AB than outside the AB. Critically, however, the interference caused by distractors presented simultaneously with T2 during the AB was reduced when T1 perceptual load was high relative to when it was low. These results suggest that increasing T1 perceptual load decreases distractor processing during the AB and that perceptual processes influence both the temporal and spatial distribution of attention.     

Asynchronous stimulus presentation in visual extinction: A psychophysical study

Patients showing visual extinction as a consequence of a unilateral brain lesion can correctly detect a single stimulus in either hemifield but fail to detect the contralesional stimulus (or at least process the stimulus less efficiently) when it is presented simultaneously with an ipsilesional stimulus. In an attempt to uncover the nature of the underlying deficit, some studies have manipulated the temporal characteristics of stimulus presentation. Contra- and ipsilesional stimuli with different stimulus onset asynchronies are typically used. In the present study, visual extinction was investigated in a group of left neglect patients (N=10) using a psychophysical paradigm with different stimulus onset asynchronies of target and distractor stimuli presented in different hemifields. Contrast thresholds for a target grating were determined with the target either in isolation or in the presence of an irrelevant distractor grating. When target and distractor gratings were presented simultaneously, neglect patients showed a significant extinction effect, i.e., a significant interference from the right hemifield distractor with left hemifield contrast sensitivity. When the right hemifield distractor preceded the left hemifield target stimulus by 250 ms, two different patterns of results were observed in the neglect patients. Five patients showed a significant improvement compared to the simultaneous presentation condition, five other patients showed a significant increase of the extinction effect. The results suggest that different underlying mechanisms, maybe due to different lesion locations, can cause extinction in neglect patients.     

Dilution of compatibility effects in Simon-type tasks depends on categorical similarity between distractors and diluters

The presence of a distracting stimulus during performance of the Stroop color-naming task leads to dilution of the Stroop effect. Because the automatic activation of word meaning may interfere with the task-relevant stimulus feature (text color; stimulus-stimulus [S-S] interference) and the response (saying the text color; stimulus-response [S-R] interference), it is unclear which of these types of interference is diluted. We introduce a new dilution paradigm using word- and arrow-based Simon tasks, in which only S-R interference is present. Participants made a left or right response to a central color target. A task-irrelevant location-word (Experiment 1) or arrow (Experiment 2) distractor adjacent to the target produced S-R compatibility effects. An additional neutral word or symbol series (diluter) was sometimes presented on the opposite side of the target from the distractor. The compatibility effect was smaller when the distractor and diluter category domains matched than when they mismatched. This result provides evidence that S-R compatibility effects are susceptible to the presence of diluters that are categorically similar to the distractors.     

场景在价值驱动注意捕获中的作用

本研究采用训练-测试范式考察场景信息在价值驱动注意捕获中的作用。实验1训练阶段将唯一性的场景信息与奖励建立联结,测试阶段发现只有当分心刺激出现在高奖励场景中才能捕获注意;实验2训练阶段将场景和颜色信息联合但分别独立预测奖励,结果发现高奖励颜色出现在任何场景中都能捕获注意。研究结果表明:(1)场景-价值联结能够引发注意捕获效应;(2)与场景相比,颜色特征在价值驱动的注意捕获中具有优势效应。     

Distractor eccentricity and its effect on selective attention

Previous research has shown conflicting results regarding the effect of distractor eccentricity on selective attention. The present study examines the relationship between a distractor's retinal location and participants' response latencies to a target while holding constant the distribution of attention. In three experiments, the participants searched for a target among several distractors. The retinal location of the critical distractor was manipulated so that it was at either a central or a peripheral location. The results show that all else being equal, an incompatible distractor causes more interference at a peripheral location than at a central location. This distractor eccentricity effect suggests that the visual system can overcome the default bias in the distribution of attention that favors a central stimulus.     

Task-irrelevant distractors in the delay period interfere selectively with visual short-term memory for spatial locations

Visual short-term memory (VSTM) enables the representation of information in a readily accessible state. VSTM is typically conceptualized as a form of “active” storage that is resistant to interference or disruption, yet several recent studies have shown that under some circumstances task-irrelevant distractors may indeed disrupt performance. Here, we investigated how task-irrelevant visual distractors affected VSTM by asking whether distractors induce a general loss of remembered information or selectively interfere with memory representations. In a VSTM task, participants recalled the spatial location of a target visual stimulus after a delay in which distractors were presented on 75% of trials. Notably, the distractor’s eccentricity always matched the eccentricity of the target, while in the critical conditions the distractor’s angular position was shifted either clockwise or counterclockwise relative to the target. We then computed estimates of recall error for both eccentricity and polar angle. A general interference model would predict an effect of distractors on both polar angle and eccentricity errors, while a selective interference model would predict effects of distractors on angle but not on eccentricity errors. Results showed that for stimulus angle there was an increase in the magnitude and variability of recall errors. However, distractors had no effect on estimates of stimulus eccentricity. Our results suggest that distractors selectively interfere with VSTM for spatial locations.     

The multi-item localization (MILO) task: measuring the spatiotemporal context of vision for action

We describe a new multi-item localization task that can be used to probe the temporal and spatial contexts of search-like behaviors. A sequence of four target letters (e.g., E, F, G, and H) was presented among four distractor letters. Observers located the targets in order. Both retrospective and prospective components of performance were examined. The retrospective component was assessed by having target items either vanish or remain once they had been located. This manipulation had little effect on search performance, suggesting that old target items can be efficiently ignored. The prospective component was assessed by shuffling future target and distractor locations after each response. This manipulation revealed that observers typically plan ahead at least one target into the future. However, even when observers cannot plan ahead, they are still able to ignore old targets. These findings suggest that both "what you did" and "what you intend to do" can influence the localization and selection of targets.     

Stimulus repetition effects on texture-based visual search by pigeons

Four experiments investigated the effects of within-session stimulus repetition on texture discrimination. Six pigeons (Columba livia) searched for a contrasting target region (color or shape) randomly embedded within a larger distractor region for food reinforcement. Experiment 1 found that repeating features of the distractors, but not those of the target, across trials increased the accuracy of target localization relative to baseline. Experiment 2 found that subsequently switching the identity of a repeated distractor feature to the target decreased accuracy. Experiment 3 found that the effects of repeating a distractor feature influenced search performance for at least 60 trials after this learning. Experiment 4 found that differential stimulus-outcome relations can produce control by repeated target features. The results are discussed in terms of the factors and strategies involved in the control of avian visual search behavior.     

Priming and intrusion errors in RSVP streams with two response dimensions

Loach and Marí-Beffa (Vis Cogn, 10:513-526, 2003) observed that a distractor stimulus, presented immediately after a behaviorally relevant target stimulus, negatively primed a related probe stimulus indicating that the distractor had been inhibited. They argued that "post-target inhibition" may be a mechanism for preventing interference from temporally proximal stimuli; interference that could potentially result in a binding/intrusion error. In order to test this hypothesis, the authors carried out two rapid serial visual presentation (RSVP) experiments in which participants had to report either the identity (Experiment 1) or color (Experiment 2) of a target letter surrounded by distractor letters. In Experiment 1, a close relationship between priming and errors was observed. When a distractor stimulus showed evidence of being inhibited the participant was less likely to commit a binding error. The opposite was true when a distractor stimulus showed evidence of being facilitated. The results of Experiment 2 showed limited evidence of the same relationship.     

Multiple sources of positive- and negative-priming effects: An event-related potential study

Event-related potential correlates of positive priming (PP) and negative priming (NP) were investigated in order to further elucidate the cognitive mechanisms involved. Thirty-six participants performed both an identity- and a location-based priming task. Repeating the target stimulus/location from the immediately preceding display produced behavioral PP. With localization, but not with identification, behavioral NP was observed when the target stimulus/location matched the preceding distractor stimulus/location. Smaller P300 amplitude accompanied identity-based PP, suggesting persisting target-specific activation. The lateralized readiness potential, an index of correct/incorrect response activation, indicated persisting central motor activation as another source of PP. Both location-based PP and NP were accompanied by reduced P1/N1 and P300 amplitudes, pointing to the involvement of inhibition of return in location-based priming. The results support the view that multiple brain processes underlie behavioral priming.     

Attention shifts and memory averaging

When observers are asked to localize the final position of a moving stimulus, judgements may be influenced by additional elements that are presented in the visual scene. Typically, judgements are biased toward a salient non-target element. It has been assumed that the non-target element acts as a landmark and attracts the remembered final target position. The present study investigated the effects of briefly flashed non-target elements on localization performance. Similar to landmark attraction, localization was biased toward these elements. However, an influence was only noted if the distractor was presented at the time of target disappearance or briefly thereafter. It is suggested that memory traces of distracting elements are only averaged with the final target position if they are highly activated at the time the target vanishes.     

Levels of visuo-spatial selection: An ERP study of negative priming

Usually, a probe target appearing in a recently ignored distractor location is less efficiently processed. This robust phenomenon is called (visuo-) spatial negative priming (SNP). Among other explanations, concepts of persisting or retrieved spatial inhibition play a major role. Two relevant issues were investigated using event-related brain potentials (ERPs). The first pertains to context sensitivity of inhibition: Is a probe distractor necessary for SNP? The second concerns levels of processing at which spatial inhibition operates: Does SNP affect perception, selection, and/or stimulus classification? A localization task with and without probe distractors was employed while 64-channel EEG was recorded. Obviously, SNP does not require a probe distractor; the distractor-absent SNP effect was larger than the distractor-present SNP effect. Distractor-present SNP had two lateralized ERP effects, N1pc amplitude reduction and N2pc amplitude increase. Smaller N1pc may indeed reflect perceptual decrement, but was inversely related to size of behavioral SNP. By contrast, only strong-SNP participants showed N2pc increase, which points to selection disadvantage due to persisting inhibition of higher-level spatial representations. Distractor-absent SNP had no N1pc/N2pc correlates; instead, reduced amplitude of a broadly distributed P300 component suggests impaired stimulus classification due to episodic retrieval of inappropriate prime information. Overall, SNP seems to emerge from relatively late stages of processing, thus challenging the idea of context-free persisting inhibition of low-level spatial representations. Furthermore, distractor-present and distractor-absent SNP are qualitatively different from each other.     

Attentional control settings prevent abrupt onsets from capturing visual spatial attention

When a visual distractor appears earlier than a visual target in a target-detection task, response time is faster if the distractor appears at the same location as the target. When a visual distractor appears concurrently with a visual target in a target-detection task, response time is slowed relative to when no distractor is presented. Both effects have been taken as evidence of the capture of visual spatial attention, yet capture by early distractors is contingent on top-down attentional control settings (ACSs), and capture by concurrent distractors is not. The present study evaluated whether this incongruity is attributable to the timing of distractors (earlier than vs. concurrently with the target), or to the employed comparisons (same location/different location vs. distractor/no distractor). Using a task that presented both early and concurrent distractors, we observed that, regardless of timing, capture was contingent on ACSs when assessed by the same-location/different-location comparison. This result suggests that, although irrelevant stimuli cause nonspatial purely stimulus-driven effects, the capture of visual spatial attention is contingent on ACSs.     

Asymmetries in a unilateral flanker task depend on the direction of the response: the role of attentional shift and perceptual grouping

Four experiments were conducted using a flanker task with 1 distractor appearing either on the left or right side of a central target. Responses were made on a keyboard aligned parallel to the displays. A larger flanker effect was obtained when the distractor was on the same side as the response. Two factors account for this asymmetry. First, when the flanker and target are identical, the 2 form a group that is assigned a spatial tag, creating a form of the Simon effect on the basis of the compatibility between the response keys and the group. Second, preparation of a lateralized response appears to entail a shift of visual attention in the corresponding direction, thus enhancing processing of the flanker on the response side. Consistent with the 2nd hypothesis, participants were more likely to correctly recognize letters that were briefly presented at the distractor position on the same side as the response.