Learning to suppress a distractor may not be unconscious

The additional singleton task has become a popular paradigm to explore visual statistical learning and selective attention. In this task, participants are instructed to find a different-shaped target among a series of distractors as fast as possible. In some trials, the search display includes a singleton distractor with a different colour, making search harder. This singleton distractor appears more often in one location than in all the remaining locations. The typical results of these experiments show that participants learn to ignore the area of the screen that is more likely to contain the singleton distractor. It is often claimed that this learning takes place unconsciously, because at the end of the experiment participants seem to be unable to identify the location where the singleton distractor appeared most frequently during the task. In the present study, we tested participants’ awareness in three high-powered experiments using alternative measures. Contrary to previous studies, the results show clear evidence of explicit knowledge about which area of the display was more likely to contain the singleton distractor, suggesting that this type of learning might not be unconscious.

Is probabilistic cuing of visual search an inflexible attentional habit? A meta-analytic review

AbstractIn studies on probabilistic cuing of visual search, participants search for a target among several distractors and report some feature of the target. In a biased stage the target appears more frequently in one specific area of the search display. Eventually, participants become faster at finding the target in that rich region compared to the sparse region. In some experiments, this stage is followed by an unbiased stage, where the target is evenly located across all regions of the display. Despite this change in the spatial distribution of targets, search speed usually remains faster when the target is located in the previously rich region. The persistence of the bias even when it is no longer advantageous has been taken as evidence that this phenomenon is an attentional habit. The aim of this meta-analysis was to test whether the magnitude of probabilistic cuing decreases from the biased to the unbiased stage. A meta-analysis of 42 studies confirmed that probabilistic cuing during the unbiased stage was roughly half the size of cuing during the biased stage, and this decrease persisted even after correcting for publication bias. Thus, the evidence supporting the claim that probabilistic cuing is an attentional habit might not be as compelling as previously thought.

Feature distribution learning by passive exposure

Humans can rapidly estimate the statistical properties of groups of stimuli, including their average and variability. But recent studies of so-called Feature Distribution Learning (FDL) have shown that observers can quickly learn even more complex aspects of feature distributions. In FDL, observers learn the full shape of a distribution of features in a set of distractor stimuli and use this information to improve visual search: response times (RT) are slowed if the target feature lies inside the previous distractor distribution, and the RT patterns closely reflect the distribution shape. FDL requires only a few trials and is markedly sensitive to different distribution types. It is unknown, however, whether our perceptual system encodes feature distributions automatically and by passive exposure, or whether this learning requires active engagement with the stimuli. In two experiments, we sought to answer this question. During an initial exposure stage, participants passively viewed a display of 36 lines that included one orientation singleton or no singletons. In the following search display, they had to find an oddly oriented target. The orientations of the lines were determined either by a Gaussian or a uniform distribution. We found evidence for FDL only when the passive trials contained an orientation singleton. Under these conditions, RT decreased as a function of the orientation distance between the target and the exposed distractor distribution. These results suggest that FDL can occur by passive exposure, but only if an orientation singleton appears during exposure to the distribution.

Attentional capture by signals of food and drink reward persists following outcome devaluation

Attention, the mechanism that prioritises stimuli in the environment for further processing, plays an important role in behavioural choice. In the current study we investigated the automatic orienting of attention to cues that signal reward. Such attentional capture occurs despite negative consequences, but the sensitivity of this counterproductive and reflexive behaviour to shifts in outcome value has not yet been investigated. Thirsty participants completed a visual-search task, in which the colour of a distractor stimulus in the search display signalled whether participants would earn water or potato chips for making a rapid eye movement to a diamond target, but looking at the coloured distractor was punished by omission of the signalled reward. Nevertheless, participants looked at the water-signalling distractor more frequently than the chips-signalling distractor. Half the participants then drank water ad libitum before continuing with the visual-search task. Although the water was now significantly less desirable for half of the participants, there was no difference between groups in the tendency for the water-signalling distractor to capture attention. These findings suggest that once established, attentional bias to signals of food and drink rewards persists, even when those outcomes are no longer valuable. This suggests a ‘habit-like’ attentional mechanism which prioritises reward stimuli in the environment for further action, regardless of whether those stimuli are aligned with current goals, or currently desired.

The development of foraging organization

In foraging tasks multiple targets must be found within a single display. The targets can be of one or more types, typically surrounded by numerous distractors. Visual attention has traditionally been studied with single target search tasks but adding more targets to the search display results in several additional measures of interest, such as how attention is oriented to different features and locations over time. We measured foraging among five age groups: Children in grades 1, 4, 7, and 10, as well as adults, using both simple feature foraging tasks and more challenging conjunction foraging tasks, with two target types per task. We assessed participants’ foraging organization, or systematicity when selecting all the targets within the foraging display, on four measures: Intertarget distance, number of intersections, best-r, and the percentage above optimal path length (PAO). We found that foraging organization increases with age, in both simple feature-based foraging and more complex foraging for targets defined by feature conjunctions, and that feature foraging was more organized than conjunction foraging. Separate analyses for different target types indicated that children’s, and to some extent adults’, conjunction foraging consisted of two relatively organized foraging paths through the display where one target type is exhaustively selected before the other target type is selected. Lastly, we found that the development of foraging organization is closely related to the development of other foraging measures. Our results suggest that measuring foraging organization is a promising avenue for further research into the development of visual orienting.

Simulated central vision loss does not impair implicit location probability learning when participants search through simple displays

Central vision loss disrupts voluntary shifts of spatial attention during visual search. Recently, we reported that a simulated scotoma impaired implicit spatial attention towards regions likely to contain search targets. In that task, search items were overlaid on natural scenes. Because natural scenes can induce explicit awareness of learned biases leading to voluntary shifts of attention, here we used a search display with a blank background less likely to induce awareness of target location probabilities. Participants searched both with and without a simulated central scotoma: a training phase contained targets more often in one screen quadrant and a testing phase contained targets equally often in all quadrants. In Experiment 1, training used no scotoma, while testing alternated between blocks of scotoma and no-scotoma search. Experiment 2 training included the scotoma and testing again alternated between scotoma and no-scotoma search. Response times and saccadic behaviors in both experiments showed attentional biases towards the high-probability target quadrant during scotoma and no-scotoma search. Whereas simulated central vision loss impairs implicitly learned spatial attention in the context of natural scenes, our results show that this may not arise from impairments to the basic mechanisms of attentional learning indexed by visual search tasks without scenes.

Is probabilistic cuing of visual search an inflexible attentional habit? A meta-analytic review

In studies on probabilistic cuing of visual search, participants search for a target among several distractors and report some feature of the target. In a biased stage the target appears more frequently in one specific area of the search display. Eventually, participants become faster at finding the target in that rich region compared to the sparse region. In some experiments, this stage is followed by an unbiased stage, where the target is evenly located across all regions of the display. Despite this change in the spatial distribution of targets, search speed usually remains faster when the target is located in the previously rich region. The persistence of the bias even when it is no longer advantageous underpins the claim that this phenomenon is a habit-like process. The aim of this meta-analysis was to test whether the magnitude of probabilistic cuing decreases from the biased to the unbiased stage. A multi-level random-effects meta-analysis of 42 studies confirmed that probabilistic cuing during the unbiased stage was roughly half the size of cuing during the biased stage, and this decrease persisted even after correcting for publication bias. We propose that probabilistic cuing is better understood as evidence of top-down attentional control than as an attentional habit.

Attentional Templates Are Sharpened through Differential Signal Enhancement, Not Differential Allocation of Attention

In visual search, the internal representation of the target feature is referred to as attentional template. The attentional template can be broad or precise depending on the task requirements. In singleton search, the attentional template is broad because the target is the only colored element in the display. In feature search, a precise attentional template is required because the target is in a specific color in an array of varied colors. To measure the precision of the attentional template, we used a cue-target paradigm where cueing benefits decrease when the cue color differs from the target color. Consistent with broad and precise attentional templates, the decrease of cueing effects was stronger in feature than in singleton search. Measurements of ERPs showed that the N2pc elicited by the cue decreased with increasing color difference, suggesting that attention was more strongly captured by cues that were similar to the target. However, the cue-elicited N2pc did not differ between feature and singleton search, making it unlikely to reflect the mechanism underlying attentional template precision. Furthermore, there was no evidence for attentional suppression as there was no cue-elicited PD, even in conditions where the cueing benefit turned into a same-location cost. However, an index of signal enhancement, the contralateral positivity, reflected attention template precision. In general, there was sensory enhancement of the stimulus appearing at the cued location in the search display. With broad attentional templates, any stimulus at the cued location was enhanced, whereas enhancement was restricted to target-matching colors with precise attentional templates.

Contextual Cueing Effect Under Rapid Presentation

In contextual cueing, previously encountered context tends to facilitate the detection of the target embedded in it than when the target appears in a novel context. In this study, we investigated whether the contextual cueing could develop at early time when the search display was presented briefly. In four experiments, participants searched for a target T in an array of distractor Ls. The results showed that with a rather short presentation time of the search display, participants were able to learn the spatial context and speeded up their response time overall, with the learning effect lasting for a long period. Specifically, the contextual cueing effect was observed either with or without a mask after a duration of 300-ms presentation of the search display. Such a context learning under rapid presentation could not operate only with the local context information repeated, thus suggesting that a global context was required to guide spatial attention when the viewing time of the search display was limited. Overall, these findings indicate that contextual cueing might arise at an “early,” target selection stage and that the global context is necessary for the context learning under rapid presentation to function.