Separate mechanisms recruited by exogenous and endogenous spatial cues: evidence from a spatial Stroop paradigm

The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was preceded by a central, symbolic, informative cue. The 2 types of cues modulated the spatial Stroop effect in opposite ways, with endogenous cues producing larger spatial Stroop effects for valid trials and exogenous cues producing smaller spatial Stroop effects for valid trials. In Experiments 2A and 2B, the influence of peripheral noninformative and peripheral informative cues on the spatial Stroop effect was directly compared. The spatial Stroop effect was smaller for valid than for invalid trials for both types of cues. These results point to a distinction between the influence of central and peripheral attentional cues on performance and are not consistent with a unitary view of endogenous and exogenous attention.     

Training attention: Interactions between central cues and reflexive attention

Three experiments are reported in which we investigate whether the recently reported interactions between central cues (e.g., arrows) and reflexive attention are attributable to the overlearned spatial properties of certain central cues. In all three experiments, a nonpredictive cue with arbitrary spatial properties (a colour patch) is presented prior to a detection target in the left or right visual field. Reaction times to detect targets are compared before and after a training session in which participants are trained to associate each colour patch with left and right space, either via a target detection task in which colour predicts target location 100% of the time (Experiments 1 and 3), or via a left/right motor movement as a function of colour (Experiments 2 and 3). In the first two experiments, a small but highly significant training effect is observed. Participants are approximately 10 ms faster to detect targets at congruent locations relative to incongruent locations after training relative to before training, despite the fact that cue colour was nonpredictive during the test sessions. In Experiment 3, the length of the training session is increased and the magnitude of the training effect also increases as a result. Implications for the interaction between central cues and reflexive attention, as well as premotor theory of attention, are discussed.     

Selectively ignoring locations does not modulate contingent involuntary orienting,but selectively attending does

Attending to a location in the visual field facilitates processing of objects in that location, and numerous studies have revealed processing benefits by precuing target locations. Recent studies have also demonstrated that precuing a location to ignore reduces distraction by items in that location; however, precuing a feature (colour) to ignore increases distractor interference, at least before a template for rejection is established. Thus, locations, not features, can be selectively ignored. The present study used a spatial cuing task to examine whether featurally-relevant items are selected when they appear in ignored locations. The results revealed contingent attentional capture by target-relevant cues (red cue when searching for red targets, but not for onset targets), even when the cue appeared in a location that was ignored. Importantly, this was equivalent to contingent capture elicited by cues in non-ignored locations. However, when observers were precued to the target location, contingent capture was largely eliminated. The results suggest salient items with target-relevant features are selected from selectively ignored locations, but focusing attention onto a location can preclude capture by salient and target-relevant items.     

Active inhibition of a distractor word: the distractor precue benefit in the Stroop color-naming task

The current study investigated attentional control through active inhibition of the identity of the distractor. Adapting a Stroop paradigm, the distractor word was presented in advance and made to disappear, followed by the presentation of a Stroop stimulus. Participants were instructed to inhibit the distractor in order to reduce its interference. Experiments 1 and 2 demonstrated that the distractor precue facilitated Stroop color naming by reducing Stroop interference. Experiment 3 demonstrated beneficial effects of the distractor precue when congruent trials were introduced. Experiment 4 showed that the distractor precue benefit was observed when the cue and target were in different forms. Experiment 5 indicated that if the item used as the cue became the target, naming it took longer in order to overcome the inhibitory effect. Experiment 6 demonstrated that the benefit of the distractor precue was not observed when the cue was uninformative. Finally, Experiment 7 demonstrated that active inhibition required working-memory resources to operate. This study suggests that the best explanation for the distractor precue benefit is the active inhibition account.     

Visual word recognition: reattending to the role of spatial attention

Three experiments examine whether spatial attention and visual word recognition processes operate independently or interactively in a spatially cued lexical-decision task. Participants responded to target strings that had been preceded first by a prime word at fixation and then by an abrupt onset cue either above or below fixation. Targets appeared either in the cued (i.e., valid) or uncued (i.e., invalid) location. The proportion of validly cued trials and the proportion of semantically related prime-target pairs were manipulated independently. It is concluded that spatial attention and visual word recognition processes are best seen as interactive. Spatial attention affects word recognition in 2 distinct ways: (a) it affects the uptake of orthographic information, possibly acting as "glue" to hold letters in their proper places in words, and (b) it (partly) determines whether or not activation from the semantic level feeds down to the lexical level during word recognition.     

Basic processes in reading: Is visual word recognition obligatory?

Visual word recognition is commonly argued to be automatic in the sense that it is obligatory and ballistic. The present experiments combined Stroop and visual search paradigms to provide a novel test of this claim. An array of three, five, or seven words including one colored target (a word in Experiments 1 and 2, a bar in Experiment 3) was presented to participants. An irrelevant color word also appeared in the display and was either integrated with or separated from the colored target. The participants classified the color of the single colored item in Experiments 1 and 3 and determined whether a target color was present or absent in Experiment 2. A Stroop effect was observed in Experiment 1 when the color word and the color target were integral, but not when the color word and the color target were separated. No Stroop effect was observed in Experiment 2. Visual word recognition is contingent on both the distribution of spatial attention and task demands.     

Interactive activation in visual word recognition: constraints imposed by the joint effects of spatial attention and semantics

Two lexical-decision experiments investigated the effects of semantic priming and stimulus intensity when target location varied and was cued by an abrupt onset. In Experiment 1, the spatial cue was a good predictor of target location, and in Experiment 2 it was not. The results indicate that word recognition processes were postponed until spatial attention was focused on the target and that whether attention further affected word recognition depended on cue validity. The joint effects of cue validity and priming interacted when cue validity was high but were additive when cue validity was low. The joint effects of stimulus intensity and semantic priming also varied according to cue validity (i.e., interactive when high and additive when low). The results are discussed in terms of their implications for visual word recognition, the distinction between exogenous and endogenous spatial attention, and how attention is affected by visual word recognition processes.     

Impaired color word processing at an unattended location: Evidence from a Stroop task combined with inhibition of return

A Stroop task with separate color bar and color word stimuli was combined with an inhibition-of-return procedure to examine whether visual attention modulates color word processing. In Experiment 1, the color bar was presented at the cued location and the color word at the uncued location, or vice versa, with a 100- or 1,050-msec stimulus onset asynchrony (SOA) between cue and Stroop stimuli. In Experiment 2, on Stroop trials, the color bar was presented at a central fixated location and the color word at a cued or uncued location above or below the color bar. In both experiments, with a 100-msec SOA, the Stroop effect was numerically larger when the color word was displayed at the cued location than when it was displayed at the uncued location, but with the 1,050-msec SOA, this relation between Stroop effect magnitude and location was reversed. These results provide evidence that processing of the color word in the Stroop task is modulated by the location to which visual attention is directed.     

Letter and word code interactions elicited by normally displayed words

The dependence of visual word recognition on letter processing was investigated by measuring the effect of a cue word on subsequent target word processing for various degrees of cue/ target similarity. Using a simultaneous matching task (Experiments 1 and 2), modest facilitation was found for identical cue/target items only, whereas items that differed by a single letter led to substantial interference. Targets that shared internal or external letters with cues yielded latencies comparable to those for neutral or different cue conditions. The identical facilitation and high-similarity interference was also found in a lexical decision task under normal display conditions (Experiment 3). However, when direct letter processing was measured using spatially transformed targets (Experiment 4), large facilitatory effects were found for similar as well as for identical cue/target conditions. Although both letter and word codes appear to be activated by normally displayed words, such word code activity may not routinely depend upon letter code outputs.     

Attentional shifts to emotionally charged cues: Behavioural and erp data

Abstract

When information activated in memory involves emotional associations, the ability to shift attention away from an emotional cue is impaired compared to an emotionally neutral cue. The purpose of the present study was to investigate how emotional stimuli modulate attentional processes, and how this is reflected in localised brain electrical activity. Eight emotion and eight neutral words served as cues in a covert attention spatial orienting task. The cues were either valid or invalid indicators of which hemifield the target would be presented to. In the remaining trials, no cue was presented prior to the target. Twenty subjects were instructed to manually respond to the target as fast as possible. Event-related potentials (ERPs) showed an enhanced P3 component to the emotion words. The ERPs to the target showed enhanced P1 and P3 components on invalid trials, with emotional cues. There were faster reaction times (RTs) to validly cued targets, but only when the emotion words served as cues. The results demonstrated that the emotional cues elicited sustained focused attention, facilitating an engage mechanism of spatial orienting.     

An electrophysiological study of attention capture by salience: Does rarity enable capture?

Several behavioural studies have suggested that rarity is critical for enabling irrelevant, salient objects to capture attention. We tested this hypothesis using the N2pc thought to reflect attentional allocation. A cue display was followed by a target display in which participants identified the letter in a specific colour. Experiment 1 pitted rare, irrelevant abrupt onset cues (appearing on only 20% of trials) against target-relevant colour cues. The relevant colour cue produced large N2pc and cue validity effects even when competing with a rare, salient, simultaneous abrupt onset. Similar results occurred even when abrupt onset frequency was reduced to only 10% of trials (Experiment 2). Experiment 3 examined rare, irrelevant colour singleton cues (20% of trials). Despite being rare and salient, these singleton cues produced no N2pc or cue validity effect indicating little attentional capture. Experiment 4 greatly increased colour cue salience by adding four background boxes, increasing colour contrast and tripling the cue display duration (from 50 to 150 ms). Small cue validity and N2pc effects were obtained, but did not strongly depend on degree of rarity (20% vs. 100%). We argue that rarity by itself is neither necessary nor sufficient to produce attention capture.     

Attentional asymmetries in a visual orienting task are related to temperament

Spatial asymmetries are an intriguing feature of directed attention. Recent observations indicate an influence of temperament upon the direction of these asymmetries. It is unknown whether this influence generalises to visual orienting behaviour. The aim of the current study was therefore to explore the relationship between temperament and measures of spatial orienting as a function of target hemifield. An exogenous cueing task was administered to 92 healthy participants. Temperament was assessed using Carver and White's (1994) Behavioural Inhibition System and Behavioural Activation System (BIS/BAS) scales. Individuals with high sensitivity to punishment and low sensitivity to reward showed a leftward asymmetry of directed attention when there was no informative spatial cue provided. This asymmetry was not present when targets were preceded by spatial cues that were either valid or invalid. The findings support the notion that individual variations in temperament influence spatial asymmetries in visual orienting, but only when lateral targets are preceded by a non-directional (neutral) cue. The results are discussed in terms of hemispheric asymmetries and dopamine activity.     

Focus on the positive: Anxiety modulates the effects of emotional stimuli on hemispheric attention

People with high levels of trait anxiety are said to orient attention selectively to threatening stimuli ( and ), but this effect is sometimes difficult to replicate. We suggest a reason for this difficulty is that typical tests of the spatial attention bias in anxiety failed to consider together: (1) the differential effects of positive and threatening stimuli on attention in anxiety, (2) the separate contributions of each hemisphere to the attention bias, and (3) whether the attention bias in anxiety is restricted to orienting or can be observed more strongly in the conflict or alerting networks of attention. We compared the effects of schematic angry, happy, and neutral face cues using a lateralized version of Posner’s Attention Network Task (Lateralized Attention Network Test) which distinguishes spatial Orienting Cost (due to an invalid cue; disengagement) from spatial Orienting Benefit (due to a valid cue; hypervigilance), and which considers executive Conflict resolution and Alerting in addition to spatial Orienting in each hemisphere separately. We tested participants with high and low trait anxiety measured by the STAI-TA (Spielberger, Gorsuch, & Lushene, 1983). Surprisingly, happy face cues rather than angry face cues interacted with target visual field and participant level of anxiety. Happy face cues presented to participants with low anxiety elicited maximal Orienting Benefit and minimal Orienting Cost for targets presented to the left visual field. Anxious individuals failed to benefit from happy cues in the left visual field. We suggest that lateralized positive cues can provide a more sensitive index of attention changes in anxiety than is provided by centrally-presented threatening cues.     

Poor vigilance affects attentional orienting triggered by central uninformative gaze and arrow cues

Behaviour and neuroimaging studies have shown that poor vigilance (PV) due to sleep deprivation (SD) negatively affects exogenously cued selective attention. In the current study, we assessed the impact of PV due to both partial SD and night-time hours on reflexive attentional orienting triggered by central un-informative eye-gaze and arrow cues. Subjective mood and interference performance in emotional Stroop task were also investigated. Twenty healthy participants performed spatial cueing tasks using central directional arrow and eye-gaze as a cue to orient attention. The target was a word written in different coloured inks. The participant’s task was to identify the colour of the ink while ignoring the semantic content of the word (with negative or neutral emotional valence). The experiment took place on 2 days. On the first day, each participant performed a 10-min training session of the spatial cueing task. On the second day, half of participants performed the task once at 4:30 p.m. (BSL) and once at 6:30 a.m. (PV), whereas the other half performed the task in the reversed order. Results showed that mean reaction times on the spatial cueing tasks were worsened by PV, although gaze paradigm was more resistant to this effect as compared to the arrow paradigm. Moreover, PV negatively affects attentional orienting triggered by both central un-informative gaze and arrow cues. Finally, prolonged wakefulness affects self-reported mood but does not influence interference control in emotional Stroop task.     

Automaticity in reading and the Stroop task: testing the limits of involuntary word processing

We investigated the parameters of involuntary word reading in the Stroop task in 7 experiments. Experiments 1-4 varied response modality and the presence of congruent word trials in a test of the claim that presenting a Stroop color word with only one letter in the target color eliminates the Stroop effect. Experiments 5 and 6 addressed the roles of spatial attention and orthographic processing as possible mechanisms behind the reduction of Stroop effects with the single-letter format. Experiment 7 investigated the limits of involuntary reading under optimal conditions for selective processing of rectangular color patch targets. We found that the single-letter format reduced but never eliminated Stroop effects, spatial attention but not orthographic processing plays a role in the effect of the single-letter format, and word reading is not completely prevented even with austere presentation conditions. We conclude with a defense of the involuntariness criterion for automaticity in the Stroop task, particularly when word reading is viewed in the context of a skilled performance.     

Spatial attention as a necessary preliminary to early processes in reading.

One major theory of the relation between spatial attention and visual word recognition holds that the former is a necessary condition for the latter to begin. A different major theory asserts that although spatial attention can facilitate the latter, it is not a necessary condition. These two theories were pitted against each other experimentally. Spatial attention was operationalized in terms of the effect of a spatial precue on the time to name a target word that appeared above or below fixation. A masked prime word was presented before the target. The critical difference between experiments was cue validity (50% in Experiments 1a and 2a and 100% in Experiments 1b and 2b). Repetition priming was observed when the prime appeared in the uncued prime location in Experiments la and 2a but not in Experiments 1b or 2b. These results are inconsistent with the claim that visual word recognition does not depend on spatial attention. Discussion centres on the distribution of spatial attention across target locations as a function of cue validity.     

眼睛注视线索提示效应: 内源性注意还是外源性注意?

采用改进的Posner视-空间线索提示范式, 对眼睛注视线索提示效应(eyes gaze cueing effect)的加工机制进行了探讨。实验一考察注视提示线索对空间Stroop效应的影响; 实验二考察注视提示线索对特征抽取和特征整合的影响。实验结果显示: 注视线索提示有效时的空间Stroop效应显著大于提示无效的情景; 在单一特征搜索与特征联合搜索任务中, 注视线索提示效应无差别。这说明, 注视线索通过在头脑里形成空间方位表征诱导注意转移; 注视线索通过影响特征抽取、而非特征整合阶段, 对客体加工产生易化。本研究支持注视线索提示效应属于内源性注意的观点。     

Attentional capture by singletons is contingent on top-down control settings: Evidence from electrophysiological measures

The present study examined whether the capture of spatial attention is driven by stimulus salience (e.g., object uniqueness) or by a match to current attentional control settings (contingent capture). We measured the N2pc effect, a component of the event-related brain potential thought to reflect lateralized attentional allocation. On every trial, a noninformative cue display containing a colour singleton box was followed by a target display of letters. Participants searched for a target letter in a specified colour (in Experiments 1–3) or within a specified shape (in Experiment 4) while ignoring other stimuli. The key manipulation was whether the singleton cue contained the target-defining feature (e.g., a specific colour). Experiment 1 revealed signs of attention capture—a cue validity effect and an N2pc effect—only for singleton cues that contained the target-defining feature. This pattern persisted even when we increased the salience of the singleton box (Experiments 2 and 3). Irrelevant colour singletons also failed to produce a significant N2pc effect when the target was defined based on shape rather than colour (Experiment 4). We conclude that attention capture is strongly contingent on top-down attentional control settings, not bottom-up stimulus salience.     

内源性注意与外源性注意的跨通道比较

该研究利用空间线索技术的实验模式,考察跨视觉和听觉通道的内源性选择注意与外源性选择性注意的相互关系。实验结果表明：(1)听觉中央线索在较长的SOA(至少500毫秒)条件下,可以引导内源性空间选择性注意;同时外周线索突现也能自动化地吸引部分注意资源。(2)听觉和视觉选择注意是分离的加工通道,但二者之间存在相互联系。