Singleton Target Research Articles

Attending is not enough: Responding to targets is needed for across-trial statistical learning

Recent evidence shows that observers are able to learn across-trial regularities as indicated by faster responses to targets whose location was predicted by the target’s location on the preceding trial. The present study investigated whether responding to both targets of the pair, as was the case in studies thus far, was needed for learning to occur. Participants searched for a shape singleton target and responded to the line inside. There were two across-trial predicting-predicted regularities regarding target locations: if the target appeared at one specific location on a given trial, it would appear at another specific location on the next trial. Unlike previous experiments, for one of these regularity pairs a response was only needed on either the first or the second target in the pair. Experiment 1 showed that across-trial learning only occurred when responding was required to both targets of a pair. If the response to one target of a pair had to be withheld, no learning occurred. Experiment 2 showed that the absence of learning cannot be attributed to carry-over inhibition resulting from not having to respond. After learning across-trial contingencies, learning remained in place even when the response to the first target of the pair had to be withheld. Our findings show that the execution of the (arbitrary) simple key-press response for both trials of the pair was needed for across-trial statistical learning to occur, whereas solely attending target locations did not result in any learning.

Relative saliency affects attentional capture and suppression of color and face singleton distractors: evidence from event-related potential studies.

Prior research has yet to fully elucidate the impact of varying relative saliency between target and distractor on attentional capture and suppression, along with their underlying neural mechanisms, especially when social (e.g. face) and perceptual (e.g. color) information interchangeably serve as singleton targets or distractors, competing for attention in a search array. Here, we employed an additional singleton paradigm to investigate the effects of relative saliency on attentional capture (as assessed by N2pc) and suppression (as assessed by PD) of color or face singleton distractors in a visual search task by recording event-related potentials. We found that face singleton distractors with higher relative saliency induced stronger attentional processing. Furthermore, enhancing the physical salience of colors using a bold color ring could enhance attentional processing toward color singleton distractors. Reducing the physical salience of facial stimuli by blurring weakened attentional processing toward face singleton distractors; however, blurring enhanced attentional processing toward color singleton distractors because of the change in relative saliency. In conclusion, the attentional processes of singleton distractors are affected by their relative saliency to singleton targets, with higher relative saliency of singleton distractors resulting in stronger attentional capture and suppression; faces, however, exhibit some specificity in attentional capture and suppression due to high social saliency.

Statistical learning of motor preparation.

Statistical learning, the process of extracting regularities from the environment, is one of the most fundamental abilities playing an essential role in almost all aspects of human cognition. Previous studies have shown that attentional selection is biased toward locations that are likely to contain a target and away from locations that are likely to contain a distractor. The current study investigated whether participants can also learn to extract that a specific motor response is more likely when the target is presented at specific locations within the visual field. To that end, the additional singleton paradigm was adapted such that when the singleton target was presented at one specific location, one response (e.g., right index finger) was more likely than the other (e.g., right middle finger) and the reverse was true for another location. The results show that participants learned to extract that a particular motor response is more likely when the singleton target (which was unrelated to the response) was presented at a specific location within the visual field. The results also suggest that it is the location of the target and not its shape that is associated with the biased response. This learning cannot be considered as being top-down or conscious as participants showed little, if any, awareness of the response biases present. The results are discussed in terms of the event coding theory. The study increases the scope of statistical learning and shows how individuals adapt automatically, without much awareness, to the regularities present in the environment. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Retinal eccentricity modulates saliency-driven but not relevance-driven visual selection.

Where we move our eyes during visual search is controlled by the relative saliency and relevance of stimuli in the visual field. However, the visual field is not homogeneous, as both sensory representations and attention change with eccentricity. Here we present an experiment investigating how eccentricity differences between competing stimuli affect saliency- and relevance-driven selection. Participants made a single eye movement to a predefined orientation singleton target that was simultaneously presented with an orientation singleton distractor in a background of multiple homogenously oriented other items. The target was either more or less salient than the distractor. Moreover, each of the two singletons could be presented at one of three different retinal eccentricities, such that both were presented at the same eccentricity, one eccentricity value apart, or two eccentricity values apart. The results showed that selection was initially determined by saliency, followed after about 300 ms by relevance. In addition, observers preferred to select the closer over the more distant singleton, and this central selection bias increased with increasing eccentricity difference. Importantly, it largely emerged within the same time window as the saliency effect, thereby resulting in a net reduction of the influence of saliency on the selection outcome. In contrast, the relevance effect remained unaffected by eccentricity. Together, these findings demonstrate that eccentricity is a major determinant of selection behavior, even to the extent that it modifies the relative contribution of saliency in determining where people move their eyes.

Feature intertrial priming biases attentional priority: Evidence from the capture-probe paradigm.

Prior experience has a strong impact on search performance, and most recent models of attention incorporate selection history as an important source of attentional guidance. Here, we focused on feature intertrial priming, a robust effect showing that responses to a singleton target are considerably faster when its unique feature repeats versus changes across successive trials. Previous studies showed that such target repetition does not reliably reduce the interference exerted by a salient distractor. This finding has been taken to indicate that target repetition does not enhance the target's competitive edge relative to the salient distractor. Therefore, it challenges the notion that intertrial priming modulates attentional priority. Here, we suggest that this inference may be misguided because the interpretation of distractor interference as a measure of the attentional priority of the salient distractor relative to the target is incorrect. To obtain a more direct measure of the impact of feature intertrial priming on the target's priority relative to a salient distractor and nontargets, we used the capture-probe paradigm. Across two experiments, probe reports from the target location increased at the expense of the salient distractor and nontarget locations when the target feature repeated versus changed, whereas distractor interference was unaffected. These findings show that feature intertrial repetition influences attentional priority. They also clearly illustrate that distractor interference indexes the priority of the salient distractor relative to the nontarget it replaces, not relative to the target-a reinterpretation that has important implications for the field of attentional capture. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Little engagement of attention by salient distractors defined in a different dimension or modality to the visual search target.

Singleton distractors may inadvertently capture attention, interfering with the task at hand. The underlying neural mechanisms of how we prevent or handle distractor interference remain elusive. Here, we varied the type of salient distractor introduced in a visual search task: the distractor could be defined in the same (shape) dimension as the target, a different (color) dimension, or a different (tactile) modality (intra-dimensional, cross-dimensional, and, respectively, cross-modal distractor, all matched for physical salience); and besides behavioral interference, we measured lateralized electrophysiological indicators of attentional selectivity (the N2pc, Ppc, PD , CCN/CCP, CDA, and cCDA). The results revealed the intra-dimensional distractor to produce the strongest reaction-time interference, associated with the smallest target-elicited N2pc. In contrast, the cross-dimensional and cross-modal distractors did not engender any significant interference, and the target-elicited N2pc was comparable to the condition in which the search display contained only the target singleton, thus ruling out early attentional capture. Moreover, the cross-modal distractor elicited a significant early CCN/CCP, but did not influence the target-elicited N2pc, suggesting that the tactile distractor is registered by the somatosensory system (rather than being proactively suppressed), without, however, engaging attention. Together, our findings indicate that, in contrast to distractors defined in the same dimension as the target, distractors singled out in a different dimension or modality can be effectively prevented to engage attention, consistent with dimension- or modality-weighting accounts of attentional priority computation.

Attentional shift to the newer object in the successive and simultaneous distractors previewing search

When some distractors (old items) appear before the other distractors and the target (new items) during an inefficient visual search task, the old items are effectively excluded from the search (preview benefit). Previous studies have shown that this preview benefit is observed when items are presented in two temporal stages, namely the initial and second displays. In this situation, new and old items are defined by a single time point (i.e., new items appearing), and the newness of the items is constant through the target search. However, in the real world, the newness of items is updated by the newer objects appearing, which requires more complex computations to detect relevant information among them. The present study examined whether previewing affects the attentional shift to a newer object if multiple new items appear successively. I used the modified preview-search paradigm, which contains three temporally separated displays, and examined what happens if the singleton target appears 200 ms after other distractors appear in the third display. This successive (search) condition was compared to the simultaneous (search) condition in which no distractors were presented in the initial display, and all distractors appeared simultaneously in the second display. The results showed that attentional shift to a newer object requires more time in the successive condition than in the simultaneous condition (Experiment 1). Moreover, the search cost for the newer target would not be induced by a mere difference in the onset timings (Experiment 2) and would occur when the duration of the initial distractors was short, and thus visual marking of the initial distractors might not occur maximally (Experiment 3). Therefore, previewing degrades attentional shift to a newer object when multiple new items appear successively.

Target templates and the time course of distractor location learning

When searching for a shape target, colour distractors typically capture our attention. Capture is smaller when observers search for a fixed target that allows for a feature-specific target template compared to a varying shape singleton target. Capture is also reduced when observers learn to predict the likely distractor location. We investigated how the precision of the target template modulates distractor location learning in an additional singleton search task. As observers are less prone to capture with a feature-specific target, we assumed that distractor location learning is less beneficial and therefore less pronounced than with a mixed-feature target. Hierarchical Bayesian parameter estimation was used to fit fine-grained distractor location learning curves. A model-based analysis of the time course of distractor location learning revealed an effect on the asymptotic performance level: when searching for a fixed-feature target, the asymptotic distractor cost indicated smaller distractor interference than with a mixed-feature target. Although interference was reduced for distractors at the high-probability location in both tasks, asymptotic distractor suppression was less pronounced with fixed-feature compared to mixed-feature targets. We conclude that with a more precise target template less distractor location learning is required, likely because the distractor dimension is down-weighted and its salience signal reduced.

The eyes prefer targets nearby fixation: Quantifying eccentricity-dependent attentional biases in oculomotor selection

An important function of peripheral vision is to provide the target of the next eye movement. Here we investigate the extent to which the eyes are biased to select a target closer to fixation over one further away. Participants were presented with displays containing two identical singleton targets and were asked to move their eyes to either one of them. The targets could be presented at three different eccentricities relative to central fixation. In one condition both singletons were presented at the same eccentricity, providing an estimate of the speed of selection at each of the eccentricities. The saccadic latency distributions from this same-eccentricity condition were then used to predict the selection bias when both targets were presented at different eccentricities. The results show that when targets are presented at different eccentricities, participants are biased to select the item closest to fixation. This eccentricity-based bias was considerably stronger than predicted on the basis of saccadic latency distributions in the same-eccentricity condition. This rules out speed of processing per se as a sole explanation for such a bias. Instead, the results are consistent with attentional competition being weighted in favour of items close to fixation.

Age-related differences in frontoparietal activation for target and distractor singletons during visual search.

Age-related decline in visual search performance has been associated with different patterns of activation in frontoparietal regions using functional magnetic resonance imaging (fMRI), but whether these age-related effects represent specific influences of target and distractor processing is unclear. Therefore, we acquired event-related fMRI data from 68 healthy, community-dwelling adults ages 18-78 years, during both conjunction (T/F target among rotated Ts and Fs) and feature (T/F target among Os) search. Some displays contained a color singleton that could correspond to either the target or a distractor. A diffusion decision analysis indicated age-related increases in sensorimotor response time across all task conditions, but an age-related decrease in the rate of evidence accumulation (drift rate) was specific to conjunction search. Moreover, the color singleton facilitated search performance when occurring as a target and disrupted performance when occurring as a distractor, but only during conjunction search, and these effects were independent of age. The fMRI data indicated that decreased search efficiency for conjunction relative to feature search was evident as widespread frontoparietal activation. Activation within the left insula mediated the age-related decrease in drift rate for conjunction search, whereas this relation in the FEF and parietal cortex was significant only for individuals younger than 30 or 44 years, respectively. Finally, distractor singletons were associated with significant parietal activation, whereas target singletons were associated with significant frontoparietal deactivation, and this latter effect increased with adult age. Age-related differences in frontoparietal activation therefore reflect both the overall efficiency of search and the enhancement from salient targets.

Selection history influences an attentional decision bias toward singleton targets.

Selection history effects are ubiquitous findings that show how implicitly encoding a target's feature or location on a trial can facilitate target activation on the following trial. Although the target-defining feature (e.g., color) is usually unpredictable, it is often relevant to determining the target on a given trial. The present study used a feature priming task, like the three-item oddball search task, but varied the target-defining feature (shape) orthogonal to the priming feature (color) that could influence target activation. On any trial the target could be a color singleton or not, and the target's feature could repeat or switch between trials. Larger priming effects were seen when the current target was a color singleton than a nonsingleton. Importantly, diffusion analyses showed that pretrial selection bias contributed to these larger priming effects. The results suggest selection history facilitates target activation through an attentional decision bias to select the object with the most recently attended color, and this attentional decision is easier when the current target is also distinct.

Is Statistical Learning of a Salient Distractor's Color Implicit, Inflexible and Distinct From Inter-Trial Priming?

Being able to overcome distraction by salient distractors is critical in order to allocate our attention efficiently. Previous research showed that observers can learn to ignore salient distractors endowed with some regularity, such as a high-probability location or feature - a phenomenon known as distractor statistical learning. Unlike goal-directed attentional guidance, the bias induced by statistical learning is thought to be implicit, long-lasting and inflexible. We tested these claims with regard to statistical learning of distractor color in a high-power (N = 160) pre-registered experiment. Participants searched for a known-shape singleton target and a color singleton distractor, when present, appeared most often in one color during the learning phase, but equally often in all possible colors during the extinction phase. We used a sensitive measure of participants' awareness of the probability manipulation. The awareness test was administered after the extinction phase for one group, and after the leaning phase for another group - which was informed that the probability imbalance would be discontinued in the upcoming extinction phase. Participants learned to suppress the high-probability distractor color very fast, an effect partly due to intertrial priming. Crucially, there was only little evidence that the bias survived during extinction. Awareness of the manipulation was associated with reduced color suppression, suggesting that the bias was implicit. Finally, results showed that the awareness test was more sensitive when administered early vs. late. We conclude that learnt color suppression is an implicit bias that emerges and decays rapidly, and discuss the methodological implications of our findings.

Multisensory Rather than Unisensory Representations Contribute to Statistical Context Learning in Tactile Search.

Using a combination of behavioral and EEG measures in a tactile odd-one-out search task with collocated visual items, we investigated the mechanisms underlying facilitation of search by repeated (vs. nonrepeated) spatial distractor-target configurations ("contextual cueing") when either the tactile (same-modality) or the visual array (different-modality) context was predictive of the location of the tactile singleton target. Importantly, in both conditions, the stimulation was multisensory, consisting of tactile plus visual items, although the target was singled out in the tactile modality and so the visual items were task-irrelevant. We found that when the predictive context was tactile, facilitation of search RTs by repeated configurations was accompanied by, and correlated with, enhanced lateralized ERP markers of pre-attentive (N1, N2) and, respectively focal-attentional processing (contralateral delay activity) not only over central ("somatosensory"), but also posterior ("visual") electrode sites, although the ERP effects were less marked over visual cortex. A similar pattern-of facilitated RTs and enhanced lateralized (N2 and contralateral delay activity) ERP components-was found when the predictive context was visual, although the ERP effects were less marked over somatosensory cortex. These findings indicate that both somatosensory and visual cortical regions contribute to the more efficient processing of the tactile target in repeated stimulus arrays, although their involvement is differentially weighted depending on the sensory modality that contains the predictive information.

Targeting TOR and SnRK1 Genes in Rice with CRISPR/Cas9.

Genome targeting with CRISPR/Cas9 is a popular method for introducing mutations and creating knock-out effects. However, limited information is currently available on the mutagenesis of essential genes. This study investigated the efficiency of CRISPR/Cas9 in targeting rice essential genes: the singleton TARGET OF RAPAMYCIN (OsTOR) and the three paralogs of the Sucrose non-fermenting-1 (SNF1)-related kinase 1 (OsSnRK1α), OsSnRK1αA, OsSnRK1αB and OsSnRK1αC. Strong activity of constitutively expressed CRISPR/Cas9 was effective in creating mutations in OsTOR and OsSnRK1α genes, but inducible CRISPR/Cas9 failed to generate detectable mutations. The rate of OsTOR mutagenesis was relatively lower and only the kinase domain of OsTOR could be targeted, while mutations in the HEAT region were unrecoverable. OsSnRK1α paralogs could be targeted at higher rates; however, sterility or early senescence was observed in >50% of the primary mutants. Additionally, OsSnRK1αB and OsSnRK1αC, which bear high sequence homologies, could be targeted simultaneously to generate double-mutants. Further, although limited types of mutations were found in the surviving mutants, the recovered lines displayed loss-of-function or knockdown tor or snrk1 phenotypes. Overall, our data show that mutations in these essential genes can be created by CRISPR/Cas9 to facilitate investigations on their roles in plant development and environmental response in rice.

Proactive enhancement and suppression elicited by statistical regularities in visual search.

The present study investigated how attentional selection is affected by simultaneous statistical learning of target and distractor regularities. Participants performed an additional singleton task in which the target singleton was presented more often in one location while the distractor singleton was presented more often in another location. On some trials, instead of the search task, participants performed a probe task, in which they had to detect the offset of a probe dot. This probe task made it possible to take a peek at the proactive selection priorities just at the moment the search display was presented. The results show that observers learn the regularities present in the search display such the location that is most likely to contain the target is enhanced while the location that is most likely to contain a distractor is suppressed. We show that these contingencies can be learned simultaneously resulting in optimal selection priorities. The probe task shows that both spatial enhancement and spatial suppression are present at the moment the actual search display is presented, indicating that the attentional priority settings are proactively modulated. We claim that through statistical learning the weights within the spatial priority map of selection are set in such a way that selection is optimally adapted to the implicitly learned regularities. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Item-specific control of attention capture: An eye movement study.

Measures of attentional capture are sensitive to attentional control settings. Recent research suggests that such control settings can be linked associatively to specific items. Rapid item-specific retrieval of these control settings can then modulate measures of attentional capture. However, the processes that produce this item-specific control of attentional capture are unclear. The current study addressed this issue by examining eye-movement patterns associated with the item-specific proportion congruency effect (ISPC). Participants searched for a shape singleton target in search displays that also contained a colour singleton-the colour singleton was either the same item as the shape singleton (congruent trials) or a different item (incongruent trials). The relative proportions of congruent and incongruent trials were manipulated separately for two distinct item types that were randomly intermixed. Response times (RTs) were faster on congruent than incongruent trials, and this congruency effect was larger for high-proportion congruent (HPC) than low-proportion congruent (LPC) items. Eye movement data revealed a higher proportion of saccades towards the distractor and longer dwell times on the distractor in the HPC condition. These results suggest that item-specific associative learning can influence the strength of representation of the task goal (e.g., find the odd shape), a form of selection history effect in visual search.

More or less? Improving monocular head mounted display assisted visual search by reducing guidance precision

ObjectiveTo test six different methods of directing a user's attention in a peripheral head mounted display assisted visual search task. BackgroundEach time a user needs to shift their attention between virtual information and their environment has a cost. The faster a user can process a guiding cue and the fewer times they need to return to it, the more efficient that cue will be at directing a user's attention. The most effective method, creating a visual effect at the location of the target, is not suitable for peripheral head mounted displays. This study tests alternative guiding cues better suited to these devices. MethodParticipants searched for a singleton target hidden among 299 distractors while directed with one of six device-delivered guiding cues. Search times were recorded. ResultsA static region map was the most efficient and most preferred cue. Static and dynamic directional cues were also effective in comparison to non-guided search. Cues designed to work solely within the participants’ peripheral vision were relatively ineffective ConclusionGuidance cues that direct a user's attention to targets within the real environment do not need to precisely lead to the target. It is instead more efficient to lead a user to the general vicinity of the target quickly and then have the user revert to their natural visual search behaviour. ApplicationThis finding is broadly useful when assisting visual search tasks with handheld or worn devices which do not cover the user's full field of view. PrécisThis study tested six different methods of guiding attention in a peripheral head-mounted display assisted visual search task. This study compared static, dynamic and peripheral-vision endogenous cues to targets and found a static simple map cue both fastest and most preferred by users.

Statistical learning of across-trial regularities during serial search.

Previous studies have shown that attention becomes biased toward those locations that frequently contain a target and is biased away from locations that have a high probability to contain a distractor. A recent study showed that participants also learned regularities that exist across trials: Participants were faster to find the singleton when its location was predicted by the location of the target singleton on the previous trial. Note, however, that this across-trial statistical learning was only demonstrated for parallel search involving "pop-out" singleton targets. The current study investigated whether there is also learning of across-trial regularities when search is serial, using a T-among-Ls task. In Experiment 1, using search displays with a gray T-target among gray Ls, we found that participants did not learn the existing across-trial regularities. In Experiment 2 we used the same display and same regularities except that during the first half of the experiment the targets were colored red, allowing feature search. Critically, now participants did learn the across-trial regularities during pop-out feature search and the learned biases persisted when search was serial again. Participants were not aware of these regularities suggesting that learning was automatic and implicit. We propose that across-trial target-target associations learned during feature search shape a flexible priority map whereby the selection of the predicting location results in up-weighting of the predicted location on the next trial. This flexible priority map remained active even when search task changed dramatically from parallel to serial search. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Spatial suppression due to statistical regularities in a visual detection task

Increasing evidence demonstrates that observers can learn the likely location of salient singleton distractors during visual search. To date, the reduced attentional capture at high-probability distractor locations has typically been examined using so called compound search, in which by design a target is always present. Here, we explored whether statistical distractor learning can also be observed in a visual detection task, in which participants respond target present if the singleton target is present and respond target absent when the singleton target is absent. If so, this allows us to examine suppression of the location that is likely to contain a distractor both in the presence, but critically also in the absence, of a priority signal generated by the target singleton. In an online variant of the additional singleton paradigm, observers had to indicate whether a unique shape was present or absent, while ignoring a colored singleton, which appeared with a higher probability in one specific location. We show that attentional capture was reduced, but not absent, at high-probability distractor locations, irrespective of whether the display contained a target or not. By contrast, target processing at the high-probability distractor location was selectively impaired on distractor-present displays. Moreover, all suppressive effects were characterized by a gradient such that suppression scaled with the distance to the high-probability distractor location. We conclude that statistical distractor learning can be examined in visual detection tasks, and discuss the implications for attentional suppression due to statistical learning.

Statistical distractor learning modulates perceptual sensitivity.

The present study used perceptual sensitivity (d′) to determine the spatial distribution of attention in displays in which participants have learned to suppress a location that is most likely to contain a distractor. Participants had to indicate whether a horizontal or a vertical line, which was shown only briefly before it was masked, was present within a target shape. Critically, the target shape could be accompanied by a singleton distractor color, which when present appeared with a high probability at one display location. The results show that perceptual sensitivity was reduced for locations likely to contain a distractor, as d′ was lower for this location than for all other locations in the display. We also found that the presence of an irrelevant color singleton reduced the gain for input at the target location, particularly when the irrelevant singleton was close to the target singleton. We conclude that, through the repeated encounter with a distractor at a particular location, the weights within the attentional priority map are changed such that the perceptual sensitivity for objects presented at that location is reduced relative to all other locations. This reduction of perceptual sensitivity signifies that this location competes less for attention than all other locations.