Evidence for split foci of attention in a priming paradigm

Most models of visuospatial attention include the notion that attention is dedicated to a single location in space. However, several researchers have found evidence that under appropriate circumstances, attention may be allocated to noncontiguous locations (e.g., Awh & Pashler, 2000; Bichot, Cave, & Pashler, 1999; Kramer & Hahn, 1995). In the present experiments, the spatial distribution of attention was assessed by a novel method, perceptual latency priming: the latency benefit of an attended visual stimulus, as compared with a nonattended stimulus. Experiment 1 assessed whether observers are able to attend to two nonadjacent regions or a region of variable size. Experiment 2 tested whether, when two distant locations are attended to, the region between them is necessarily also in the focus of attention. Two further experiments controlled for objections against the method used and replicated the main results of the first two experiments. The experiments showed a robust attentional priming effect at two noncontiguous locations of the visual field, simultaneous with little or no priming of the intervening location.     

Evidence for distinct attentional bottlenecks in attention switching and attentional blink tasks

E. Weichselgartner and G. A. Sperling (1987), using rapid serial visual presentation (RSVP), estimated that attention could be moved to a new spatial location within 300-400 ms. H. J. Müller and P. M. Rabbit (1989) used a spatial cuing task and found a similar time course for voluntarily redeploying attention. A separate phenomenon known as the attentional blink (AB) also follows a similar time course, yet occurs when participants attend to a single spatial location. The present study found that attention can be shifted more quickly than previously estimated and that part of the deficit observed during searches of spatially distinct RSVP streams is due to an AB. The results support some early and late selection accounts for the temporal dynamics of visual attention and suggest different bottlenecks during visual selection. The implications for visual search and visual processing are discussed.     

Evidence for attentional processing in spatial localization

Using a dual-task methodology, this study examined the involvement of selective attention in spatial localization. Thirty participants located a single, briefly presented, peripheral target stimulus, appearing in one of 50 positions on either side of a central fixation point, with or without the requirement to identify a simultaneously presented central distractor stimulus. Results revealed a robust interference effect in localization performance at short target durations that depended on the number of the to-be-identified distractor items. This outcome provides convergent support for the role of the attentional system in spatial localization.     

Evidence for attentional capture by a surprising color singleton in visual search

Three experiments were conducted to investigate whether surprising color singletons capture attention. Participants performed a visual search task in which a target letter had to be detected among distractor letters. Experiments 1 and 2 assessed accuracy as the dependent variable. In Experiment 1, the unannounced presentation of a color singleton 500 ms prior to the letters (and in the same position as the target letter) resulted in better performance than in the preceding conjunction search segment, in which no singleton was presented, and performance was as good in this surprise–singleton trial as in the following feature search segment, in which the singleton always coincided with the target. In contrast, no improvement was observed when the color singleton was presented simultaneously with the letters in Experiment 2, indicating that attentional capture occurred later in the surprise trial than in the feature search segment. In Experiment 3, set size was varied, and reaction time was the dependent variable. Reaction time depended on set size in the conjunction search segment, but not in the surprise trial nor in the feature search segment. The results of the three experiments support the view that surprising color singletons capture attention independently of a corresponding attentional set.     

Time to guide: Evidence for delayed attentional guidance in contextual cueing

Contextual cueing experiments show that, when displays are repeated, reaction times (RTs) to find a target decrease over time even when the observers are not aware of the repetition. Recent evidence suggests that this benefit in standard contextual cueing tasks is not likely to be due to an improvement in attentional guidance (Kunar, Flusberg, Horowitz, & Wolfe, 2007). Nevertheless, we ask whether guidance can help participants find the target in a repeated display, if they are given sufficient time to encode the display. In Experiment 1 we increased the display complexity so that it took participants longer to find the target. Here we found a larger effect of guidance than in a condition with shorter RTs. Experiment 2 gave participants prior exposure to the display context. The data again showed that with more time participants could implement guidance to help find the target, provided that there was something in the search stimuli locations to guide attention to. The data suggest that, although the benefit in a standard contextual cueing task is unlikely to be a result of guidance, guidance can play a role if it is given time to develop.     

Evidence from the attentional blink for different sources of word repetition effects

T2 in an attentional blink paradigm served as a high- or low-frequency prime word for a subsequent repeated target. Consistent with research in visual word identification, only reported primes facilitated the identification of a target repeated approximately 8 s after RSVP. Priming was greater for low- than high-frequency words. Analogous with masked priming, a blinked T2 facilitated report of a repeated target occurring 318 ms after T2 in RSVP. The blinked repetition priming effect was additive with target frequency. These results indicate that: (1) the outcomes of processing prime words are a key factor in repetition priming effects, with blinked and reported T2s behaving like masked and unmasked primes, respectively, (2) there may be different sources of repetition effects, (3) there is a consistent cross-paradigm pattern of repetition effects that occurs as a function of prime–target interval and the ability to identify the word on its first and second presentation.     

Top-down control settings and the attentional blink: Evidence for nonspatial contingent capture

Previous studies have shown that spatial attention can be “captured” by irrelevant events, but only if the eliciting stimulus matches top-down attentional control settings. Here we explore whether similar principles hold for nonspatial attentional selection. Subjects searched for a coloured target letter embedded in an RSVP stream of letters inside a box centred on fixation. On critical trials, a distractor, consisting of a brief change in the colour of the box, occurred at various temporal lags prior to the target. In Experiment 1, the distractor produced a decrement in target detection, but only when it matched the target colour. Experiments 2 and 3 provide evidence that this effect does not reflect masking or the dispersion of spatial attention. The results establish that (1) nonspatial selection is subject to “capture”, (2) such capture is contingent on top-down attentional control settings, and (3) control settings for nonspatial capture can vary in specificity.     

Evidence for suppressive mechanisms in attentional selection: feature singletons produce inhibitory surrounds

Four experiments explored inhibitory mechanisms related to attentional selection. Observers viewed multielement displays and performed a form discrimination task involving a probe element. Also present in the stimulus display was a singleton element (possessing a unique color or orientation). In Experiments 1-3, probe discrimination performance was measured as a function of the distance between the probe and the singleton. Experiment 1 revealed that probe discriminations suffered when the probe was adjacent to the singleton, but improved as the spatial separation between the probe and attentionally salient singleton increased. Experiment 2 added a control condition, revealing that probe discriminations were inhibited near the singleton, but returned to control level performance with increased separation. Further, the amount of inhibition increased with larger stimulus onset asynchronies between the singleton and probe. Experiment 3 demonstrated that the extent of the inhibitory region is spatially mediated. In Experiment 4, the task was modified to one of probe detection. No inhibition was observed in the detection task, indicating that the decrease in probe discrimination performance observed in Experiments 1-3 was not due to observers' inability to detect the probe element.     

All set! Evidence of simultaneous attentional control settings for multiple target colors

Although models of visual search have often assumed that attention can only be set for a single feature or property at a time, recent studies have suggested that it may be possible to maintain more than one attentional control setting. The aim of the present study was to investigate whether spatial attention could be guided by multiple attentional control settings for color. In a standard spatial cueing task, participants searched for either of two colored targets accompanied by an irrelevantly colored distractor. Across five experiments, results consistently showed that nonpredictive cues matching either target color produced a significant spatial cueing effect, while irrelevantly colored cues did not. This was the case even when the target colors could not be linearly separated from irrelevantly cue colors in color space, suggesting that participants were not simply adopting one general color set that included both target colors. The results could not be explained by intertrial priming by previous targets, nor could they be explained by a single inhibitory set for the distractor color. Overall, the results are most consistent with the maintenance of multiple attentional control settings.     

Components of attentional biases in contamination fear: Evidence for difficulty in disengagement

Attentional bias for threat has been implicated in the contamination fear (CF) subtype of obsessive-compulsive disorder, but the components of the bias (facilitated attention versus difficulty in disengagement) and the stage of processing during which the bias occurs (early versus late stage of processing) remains unclear. Further, it is unclear whether attentional biases in CF are towards fear or disgust-related stimuli. The present study examined attentional biases in a group of individuals selected to have elevated CF (n = 23) and a control group (n = 28) using the spatial cueing task. Stimuli were neutral, disgusting, or frightening pictures presented for either 100 or 500 ms. Results revealed evidence for delayed disengagement from both fear and disgust stimuli in the CF group, but not in the control group. The effect appeared to be greater at 500 ms stimulus presentation, but did not appear to differ between fear and disgust stimuli. The CF group was associated with delayed disengagement from threat even when controlling for generic response slowing. Theoretical and clinical implications are discussed.     

Acquired distinctiveness and equivalence in human discrimination learning: Evidence for an attentional process

In a first stage of training, participants learned to associate four visual cues (two different colors and two different shapes) with verbal labels. For Group S, one label was applied to both colors and another to both shapes; for Group D, one label was applied to one color and one shape, and the other label to the other cues. When subsequently required to learn a task in which a given motor response was required to one of the colors and one of the shapes, and a different response to the other color and the other shape, Group D learned more readily than Group S. The task was designed so that the associations formed during the first stage of training could not generate differential transfer to the second stage. The results are consistent, however, with the proposal that training in which similar cues are followed by different outcomes will engage a learning process that boosts the attention paid to features that distinguish these cues.     

Evidence for an attentional component of the perceptual misalignment between moving and flashing stimuli

If a pair of dots, diametrically opposed to each other, is flashed in perfect alignment with another pair of dots rotating about the visual fixation point, most observers perceive the rotating dots as being ahead of the flashing dots (flash-lag effect). This psychophysical effect was first interpreted as the result of a perceptual extrapolation of the position of the moving dots. Also, it has been conceived as the result of differential visual latencies between flashing and moving stimuli, arising from purely sensory factors and/or expressing the contribution of attentional mechanisms as well. In a series of two experiments, we had observers judge the relative position between rotating and static dots at the moment a temporal marker was presented in the visual field. In experiment 1 we manipulated the nature of the temporal marker used to prompt the alignment judgment. This resulted in three main findings: (i) the flash-lag effect was observed to depend on the visual eccentricity of the flashing dots; (ii) the magnitude of the flash-lag effect was not dependent on the offset of the flashing dot; and (iii) the moving stimulus, when suddenly turned off, was perceived as lagging behind its disappearance location. Taken altogether, these results suggest that neither visible persistence nor motion extrapolation can account for the perceptual flash-lag phenomenon. The participation of attentional mechanisms was investigated in experiment 2, where the magnitude of the flash-lag effect was measured under both higher and lower predictability of the location of the flashing dot. Since the magnitude of the flash-lag effect significantly increased with decreasing predictability, we conclude that the observer's attentional set can modulate the differential latencies determining this perceptual effect. The flash-lag phenomenon can thus be conceived as arising from differential visual latencies which are determined not only by the physical attributes of the stimulus, such as its luminance or eccentricity, but also by attentional mechanisms influencing the delays involved in the perceptual processing.     

Goal specificity and knowledge acquisition in statistics problem solving: Evidence for attentional focus

Solving training problems with nonspecific goals (NG; i.e., solving for all possible unknown values) often results in better transfer than solving training problems with standard goals (SG; i.e., solving for one particular unknown value). In this study, we evaluated an attentional focus explanation of the goal specificity effect. According to the attentional focus view, solving NG problems causes attention to be directed to local relations among successive problem states, whereas solving SG problems causes attention to be directed to relations between the various problem states and the goal state. Attention to the former is thought to enhance structural knowledge about the problem domain and thus promote transfer. Results supported this view because structurally different transfer problems were solved faster following NG training than following SG training. Moreover, structural knowledge representations revealed more links depicting local relations following NG training and more links to the training goal following SG training. As predicted, these effects were obtained only by domain novices.     

Disrupted attentional learning in high schizotypy: Evidence of aberrant salience

The relationship between learned variations in attention and schizotypy was examined in two experiments. In Experiment 1, participants low on a negative subscale of schizotypy exhibited an explicit bias in overt attention towards stimuli that were established as predictive of a trial outcome, relative to stimuli that were irrelevant. The same participants also showed a bias in learning about these stimuli when they presented in a novel context. Neither of these effects was observed in participants high in schizotypy. In Experiment 2, participants low on the negative subscale of schizotypy exhibited faster reaction times towards a target that was cued by a stimulus that had a history of predictive validity relative to a stimulus that had a history of irrelevance. Again, this effect was not present in participants high in schizotypy. These results imply a disruption in the normal allocation of attention to cues that have predictive significance in schizotypy.     

Goal-driven attentional capture by invisible colors: Evidence from event-related potentials

We combined event-related brain potentials (ERPs) and behavioral measures to test whether subliminal visual stimuli can capture attention in a goal-dependent manner. Participants searched for visual targets defined by a specific color. Search displays served as metacontrast masks for preceding cue displays that contained one cue in the target color. Although this target-color cue was spatially uninformative, it produced behavioral spatial cuing effects and triggered an ERP correlate of attentional selection (i.e., the N2pc component). These results demonstrate that target-color cues captured attention, in spite of the fact that cue localization performance assessed in separate blocks was at chance level. We conclude that task-set contingent attentional capture is not restricted to supraliminal stimuli, but is also elicited by visual events that are not consciously perceived.     

Attention capture while switching search strategies: Evidence for a breakdown in top-down attentional control

Whereas capture experiments typically repeat a single task many times, real world cognition is characterized by frequent switching. Lien, Ruthruff, and Johnston (2010) reported that the attentional control system can rapidly and fully switch between different search settings (e.g., red to green), with no carryover and no intertrial priming. The present study examined whether this impressive flexibility is possible even when the switch is not between different features along the same dimension, but between mutually incompatible search modes. On each trial, participants were prompted to find and identify the letter that was in a specific colour (feature search mode) or was uniquely coloured (singleton search mode). Within each block, search mode was either pure or mixed; the mixed blocks contained a fixed AABB search sequence (singleton-singleton-feature-feature) in Experiment 1 and a random sequence in Experiment 2. The target display was preceded by a noninformative cue display containing a nontarget colour singleton. In pure feature search blocks, these irrelevant singleton cues were generally unable to capture attention, replicating previous findings of “contingent capture”. In mixed blocks, however, irrelevant colour singletons captured attention on feature search trials. This breakdown indicates a limitation in the sharpness of attentional control following mode switches, which might be common in the real world.     

An attentional blink for sequentially presented targets: Evidence in favor of resource depletion accounts

Several accounts of the attentional blink (AB) have postulated that this dual-target deficit occurs because of limited-capacity attentional resources being devoted to processing the first target at the expense of the second (resource depletion accounts; e.g., Chun & Potter, 1995). Recent accounts have challenged this model (e.g., Di Lollo, Kawahara, Ghorashi, & Enns, 2005; Olivers, van der Stigchel, & Hulleman, 2007), proposing instead that the AB occurs because of subjects’ inability to maintain appropriate levels of attentional control when targets are separated by distractors. Accordingly, the AB is eliminated when three targets from the same attentional set are presented sequentially in a rapid serial visual presentation (RSVP) stream. However, under such conditions poorer identification of the first target is typically observed, hinting at a potential trade-off between the first and subsequent target performances. Consistent with this hypothesis, the present study shows that an AB is observed for successive targets from the same attentional set in an RSVP stream when the first target powerfully captures attention. These results suggest that resource depletion contributes significantly to the AB.     

Involuntary transfer of a top-down attentional set into the focus of attention: Evidence from a contingent attentional capture paradigm

In the present study, we investigated whether involuntarily directing attention to a target-colored distractor causes the corresponding attentional set to enter a limited-capacity focus of attention, thereby facilitating the identification of a subsequent target whose color matches the same attentional set. As predicted, in Experiment 1, contingent attentional capture effects from a target-colored distractor were only one half to one third as large when subsequent target identification relied on the same (vs. a different) attentional set. In Experiment 2, this effect was eliminated when all of the target colors matched the same attentional set, arguing against bottomup perceptual priming of the distractor’s color as an alternative account of our findings. In Experiment 3, this effect was reversed when a target-colored distractor appeared after the target, ruling out a feature-based interference account of our findings. We conclude that capacity limitations in working memory strongly influence contingent attentional capture when multiple attentional sets guide selection.     

On the saliency of negative stimuli: Evidence from attentional blink1

Abstract: When people are asked to detect two targets from a rapid serial visual presentation (RSVP) stream, impairment of recognition of the second target (T2) can be observed if the T2 is presented several hundred milliseconds later than the first target (T1). This phenomenon is known as attentional blink, and is considered to reflect some temporal characteristic of the attentional process. The aim of the present study was to use the attentional blink paradigm to examine whether the affective meaning of the stimuli could affect the magnitude of attentional blink. In Experiment 1, the valence of the T2 (neutral, positive, and negative) was manipulated. Significant T2 detection deficit was observed with neutral and positive T2 but not with negative T2. Experiment 2 demonstrated that non‐significant attentional blink in negative T2 in Experiment 1 could be attributed to the negative affective meaning of T2. Results are discussed in terms of the high saliency of negative information.     

Self-esteem modulates attentional responses to rejection: Evidence from event-related brain potentials

Individuals with low self-esteem have been shown to exhibit an attentional bias for social rejection cues. The present study investigated whether individuals with low self-esteem would demonstrate greater reactivity to rejection-related stimuli during an attention shifting task than was exhibited by those with high self-esteem. Individuals with low self-esteem showed higher amplitude event-related potentials (ERPs) in response to rejection cues than was observed for those with high self-esteem. These results suggest that individuals with low self-esteem allocate more attentional resources to rejection cues than those with high self-esteem. Discussion will focus on the implications of these findings for understanding the connection between low self-esteem and social rejection.