Intermixed levels of visual search difficulty produce asymmetric probability learning.

When performing novel tasks, we often apply the rules we have learned from previous, similar tasks. Knowing when to generalize previous knowledge, however, is a complex challenge. In this study, we investigated the properties of learning generalization in a visual search task, focusing on the role of search difficulty. We used a spatial probability learning paradigm in which individuals learn to prioritize their search toward the locations where a target appears more often (i.e., high-probable location) than others (i.e., low-probable location) in a search display. In the first experiment, during a training phase, we intermixed the easy and difficult search trials within blocks, and each was respectively paired with a distinct high-probable location. Then, during a testing phase, we removed the probability manipulation and assessed any generalization of spatial biases to a novel, intermediate difficulty task. Results showed that, as training progressed, the easy search evoked a stronger spatial bias to its high-probable location than the difficult search. Moreover, there was greater generalization of the easy search learning than difficult search learning at test, revealed by a stronger bias toward the former's high-probable location. Two additional experiments ruled out alternatives that learning during difficult search itself is weak and learning during easy search specifically weakens learning of the difficult search. Overall, the results demonstrate that easy search interferes with difficult search learning and generalizability when the two levels of search difficulty are intermixed.

Familiarity enhances mnemonic precision but impairs mnemonic accuracy in visual working memory.

Prior stimulus familiarity has a variety of effects on visual working memory representations and processes. However, it is still unclear how familiarity interacts with the veridical correspondence between mnemonic representation and external stimuli. Here, we examined the effect of familiarity on two aspects of mnemonic correspondence, precision and accuracy, in visual working memory. Specifically, we used a hierarchical Bayesian method to model task performance in a change detection task with celebrity lookalikes (morphed faces between celebrities and noncelebrities with various ratios) as the memory stimuli. We found that familiarity improves memory precision by sharpening mnemonic representation but impairs memory accuracy by biasing mnemonic representation toward familiar faces (i.e., celebrity faces). These findings provide an integrated account of the puzzling celebrity sighting phenomena with the dissociable effects on mnemonic imprecision and bias and further highlight the importance of assessing these two aspects of memory correspondence in future research.

Memory precision for salient distractors decreases with learned suppression.

Attention operates as a cognitive gate that selects sensory information for entry into memory and awareness (Driver, 2001, British Journal of Psychology, 92, 53-78). Under many circumstances, the selected information is task-relevant and important to remember, but sometimes perceptually salient nontarget objects will capture attention and enter into awareness despite their irrelevance (Adams & Gaspelin, 2020, Attention, Perception, & Psychophysics, 82[4], 1586-1598). Recent studies have shown that repeated exposures with salient distractor will diminish their ability to capture attention, but the relationship between suppression and later cognitive processes such as memory and awareness remains unclear. If learned attentional suppression (indicated by reduced capture costs) occurs at the sensory level and prevents readout to other cognitive processes, one would expect memory and awareness to dimmish commensurate with improved suppression. Here, we test this hypothesis by measuring memory precision and awareness of salient nontargets over repeated exposures as capture costs decreased. Our results show that stronger learned suppression is accompanied by reductions in memory precision and confidence in having seen a color singleton at all, suggesting that such suppression operates at the sensory level to prevent further processing of the distractor object.

Changes in visual cortical processing attenuate singleton distraction during visual search.

The ability to suppress distractions is essential to successful completion of goal-directed behaviors. Several behavioral studies have recently provided strong evidence that learned suppression may be particularly efficient in reducing distractor interference. Expectations about a distractor's repeated location, color, or even presence are rapidly learned and used to attenuate interference. In this study, we use a visual search paradigm in which a color singleton, which is known to capture attention, occurs within blocks with high or low frequency. The behavioral results show reduced singleton interference during the high compared to the low frequency block (Won et al., 2019). The fMRI results provide evidence that the attenuation of distractor interference is supported by changes in singleton, target, and non-salient distractor representations within retinotopic visual cortex. These changes in visual cortex are accompanied by findings that singleton-present trials compared to non-singleton trials produce greater activation in bilateral parietal cortex, indicative of attentional capture, in low frequency, but not high frequency blocks. Together, these results suggest that the readout of saliency signals associated with an expected color singleton from visual cortex is suppressed, resulting in less competition for attentional priority in frontoparietal attentional control regions.

Passive exposure attenuates distraction during visual search.

Distractions are ubiquitous in our sensory environments. How do we keep them from capturing attention? Existing research has focused primarily on mechanisms of strategic control or statistical learning, both of which require knowledge (explicit or implicit) of what features belong to distractors before suppression occurs. Here, we test the hypothesis that task-free exposure to stimuli is sufficient to attenuate their effect as distractors later on. In 3 experiments, subjects were exposed to either colored or achromatic circles on "circle displays" interleaved with "target search displays." Later, new distractors were introduced into the search displays using colors from the circle displays. We consistently found that passively viewed colors produced less interference when introduced as new visual search distractors. We conclude that learning during passive exposure was due to habituation mechanisms that attenuate sensory responsivity to recurring stimuli, allowing attention to operate more efficiently to select task-relevant targets or novel stimuli. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Flexible target templates improve visual search accuracy for faces depicting emotion.

Theories of visual attention hypothesize that target selection depends upon matching visual inputs to a memory representation of the target - i.e., the target or attentional template. Most theories assume that the template contains a veridical copy of target features, but recent studies suggest that target representations may shift "off veridical" from actual target features to increase target-to-distractor distinctiveness. However, these studies have been limited to simple visual features (e.g., orientation, color), which leaves open the question of whether similar principles apply to complex stimuli, such as a face depicting an emotion, the perception of which is known to be shaped by conceptual knowledge. In three studies, we find confirmatory evidence for the hypothesis that attention modulates the representation of an emotional face to increase target-to-distractor distinctiveness. This occurs over-and-above strong pre-existing conceptual and perceptual biases in the representation of individual faces. The results are consistent with the view that visual search accuracy is determined by the representational distance between the target template in memory and distractor information in the environment, not the veridical target and distractor features.

Evidence for second-order singleton suppression based on probabilistic expectations.

Decades of research in attention have shown that salient distractors (e.g., a color singleton) tend to capture attention. However, in most studies, singleton distractors are just as likely to be present as absent. We therefore have little knowledge of how probabilistic expectations of the salient distractor's occurrence and features affect suppression. In three experiments, we explored this question by manipulating the frequency of a singleton distractor and the variability of its color within a search display. We found that increased expectations regarding the occurrence of the singleton distractor eliminated the singleton response time cost and reduced the number of first saccades to the singleton. In contrast, expectations regarding variability in the singleton color did not affect singleton capture. This was surprising and suggests the ability to suppress second-order salience over and above that of first-order features. We next inserted the probe display that included a to-be-reported letter inside each shape between search trials to measure if attention went to multiple objects. The letter in the singleton location was reported less often in the high-frequency condition, suggesting proactive suppression of expected singleton. Additionally, we found that trial-to-trial repetitions of a singleton (irrespective of its color and location) facilitated performance (i.e., singleton repetition priming), but repetitions of its specific color or location did not. Together our findings demonstrate that attentional capture by a color singleton distractor is attenuated by probabilistic expectations of its occurrence, but not of its color and location. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Distractor ignoring: strategies, learning, and passive filtering.

Our sensory environments contain more information than we can processes and successful behaviors require the ability to separate task-relevant information from task-irrelevant information. While much research on attention has focused on the mechanisms that result in selection of desired information, much less is known about how distracting information is ignored. Here we describe evidence that strategic, learned, and passive information can all contribute to better distractor ignoring. The evidence suggests that there are multiple ways in which distractor ignoring is supported that may be different than those of target selection. Future work will need to identify the mechanisms by which each source of information adjusts attentional priority such that irrelevant information is better ignored.

Learned suppression for multiple distractors in visual search.

Visual search for a target object occurs rapidly if there were no distractors to compete for attention, but this rarely happens in real-world environments. Distractors are almost always present and must be suppressed for target selection to succeed. Previous research suggests that one way this occurs is through the creation of a stimulus-specific distractor template. However, it remains unknown how information within such templates scale up with multiple distractors. Here we investigated the informational content of distractor templates created from repeated exposures to multiple distractors. We investigated this question using a visual search task in which participants searched for a gray square among colored squares. During "training," participants always saw the same set of colored distractors. During "testing," new distractor sets were interleaved with the trained distractors. The critical manipulation in each study was the distance (in color space) of the new test distractors from the trained distractors. We hypothesized that the pattern of distractor interference during testing would reveal the tuning of the suppression template: RTs should be commensurate with the degree to which distractor colors are encoded within the suppression template. Results from four experiments converged on the notion that the distractor template includes information about specific color values, but has broad "tuning," allowing suppression to generalize to new distractors. These results suggest that distractor templates, unlike target templates, encode multiple features and have broad representations, which have the advantage of generalizing suppression more easily to other potential distractors. (PsycINFO Database Record

How do magnitude and frequency of monetary reward guide visual search?

How does reward guide spatial attention during visual search? In the present study, we examine whether and how two types of reward information-magnitude and frequency-guide search behavior. Observers were asked to find a target among distractors in a search display to earn points. We manipulated multiple levels of value across the search display quadrants in two ways: For reward magnitude, targets appeared equally often in each quadrant, and the value of each quadrant was determined by the average points earned per target; for reward frequency, we varied how often the target appeared in each quadrant but held the average points earned per target constant across the quadrants. In Experiment 1, we found that observers were highly sensitive to the reward frequency information, and prioritized their search accordingly, whereas we did not find much prioritization based on magnitude information. In Experiment 2, we found that magnitude information for a nonspatial feature (color) could bias search performance, showing that the relative insensitivity to magnitude information during visual search is not generalized across all types of information. In Experiment 3, we replicated the negligible use of spatial magnitude information even when we used limited-exposure displays to incentivize the expression of learning. In Experiment 4, we found participants used the spatial magnitude information during a modified choice task-but again not during search. Taken together, these findings suggest that the visual search apparatus does not equally exploit all potential sources of spatial value information; instead, it favors spatial reward frequency information over spatial reward magnitude information.

Statistical learning modulates the direction of the first head movement in a large-scale search task.

Foraging and search tasks in everyday activities are often performed in large, open spaces, necessitating head and body movements. Such activities are rarely studied in the laboratory, leaving important questions unanswered regarding the role of attention in large-scale tasks. Here we examined the guidance of visual attention by statistical learning in a large-scale, outdoor environment. We used the orientation of the first head movement as a proxy for spatial attention and examined its correspondence with reaction time (RT). Participants wore a lightweight camera on a baseball cap while searching for a coin on the concrete floor of a 64-m(2) outdoor space. We coded the direction of the first head movement at the start of a trial. The results showed that the first head movement was highly sensitive to the location probability of the coin and demonstrated more rapid adjustment to changes in environmental statistics than RTs did. Because the first head movement occurred ten times faster than the search RT, these results show that visual statistical learning affected attentional orienting early in large-scale tasks.

Spatial scale, rather than nature of task or locomotion, modulates the spatial reference frame of attention.

Visuospatial attention is strongly biased to locations that had frequently contained a search target before. However, the function of this bias depends on the reference frame in which attended locations are coded. Previous research has shown a striking difference between tasks administered on a computer monitor and those administered in a large environment, with the former inducing viewer-centered learning and the latter environment-centered learning. Why does environment-centered learning fail on a computer? Here, we tested 3 possibilities: differences in spatial scale, the nature of task, and locomotion may each influence the reference frame of attention. Participants searched for a target on a monitor placed flat on a stand. On each trial, they stood at a different location around the monitor. The target was frequently located in a fixed area of the monitor, but changes in participants' perspective rendered this area random relative to the participants. Under incidental learning conditions, participants failed to acquire environment-centered learning even when (a) the task and display resembled those of a large-scale task and (b) the search task required locomotion. The difficulty in inducing environment-centered learning on a computer underscores the egocentric nature of visual attention. It supports the idea that spatial scale modulates the reference frame of attention.

Spatial working memory interferes with explicit, but not probabilistic cuing of spatial attention.

Recent empirical and theoretical work has depicted a close relationship between visual attention and visual working memory. For example, rehearsal in spatial working memory depends on spatial attention, whereas adding a secondary spatial working memory task impairs attentional deployment in visual search. These findings have led to the proposal that working memory is attention directed toward internal representations. Here, we show that the close relationship between these 2 constructs is limited to some but not all forms of spatial attention. In 5 experiments, participants held color arrays, dot locations, or a sequence of dots in working memory. During the memory retention interval, they performed a T-among-L visual search task. Crucially, the probable target location was cued either implicitly through location probability learning or explicitly with a central arrow or verbal instruction. Our results showed that whereas imposing a visual working memory load diminished the effectiveness of explicit cuing, it did not interfere with probability cuing. We conclude that spatial working memory shares similar mechanisms with explicit, goal-driven attention but is dissociated from implicitly learned attention.

Task specificity of attention training: the case of probability cuing.

Statistical regularities in our environment enhance perception and modulate the allocation of spatial attention. Surprisingly little is known about how learning-induced changes in spatial attention transfer across tasks. In this study, we investigated whether a spatial attentional bias learned in one task transfers to another. Most of the experiments began with a training phase in which a search target was more likely to be located in one quadrant of the screen than in the other quadrants. An attentional bias toward the high-probability quadrant developed during training (probability cuing). In a subsequent, testing phase, the target's location distribution became random. In addition, the training and testing phases were based on different tasks. Probability cuing did not transfer between visual search and a foraging-like task. However, it did transfer between various types of visual search tasks that differed in stimuli and difficulty. These data suggest that different visual search tasks share a common and transferrable learned attentional bias. However, this bias is not shared by high-level, decision-making tasks such as foraging.

Spatial reference frame of attention in a large outdoor environment.

A central question about spatial attention is whether it is referenced relative to the external environment or to the viewer. This question has received great interest in recent psychological and neuroscience research, with many but not all, finding evidence for a viewer-centered representation. However, these previous findings were confined to computer-based tasks that involved stationary viewers. Because natural search behaviors differ from computer-based tasks in viewer mobility and spatial scale, it is important to understand how spatial attention is coded in the natural environment. To this end, we created an outdoor visual search task in which participants searched a large (690 square ft), concrete, outdoor space to report which side of a coin on the ground faced up. They began search in the middle of the space and were free to move around. Attentional cuing by statistical learning was examined by placing the coin in 1 quadrant of the search space on 50% of the trials. As in computer-based tasks, participants learned and used these regularities to guide search. However, cuing could be referenced to either the environment or the viewer. The spatial reference frame of attention shows greater flexibility in the natural environment than previously found in the lab.

First saccadic eye movement reveals persistent attentional guidance by implicit learning.

Implicit learning about where a visual search target is likely to appear often speeds up search. However, whether implicit learning guides spatial attention or affects postsearch decisional processes remains controversial. Using eye tracking, this study provides compelling evidence that implicit learning guides attention. In a training phase, participants often found the target in a high-frequency, "rich" quadrant of the display. When subsequently tested in a phase during which the target was randomly located, participants were twice as likely to direct the first saccadic eye movement to the previously rich quadrant than to any of the sparse quadrants. The attentional bias persisted for nearly 200 trials after training and was unabated by explicit instructions to distribute attention evenly. We propose that implicit learning guides spatial attention but in a qualitatively different manner than goal-driven attention.

Redundancy effects in the processing of emotional faces.

How does the visual system represent the ensemble statistics of visual objects? This question has received intense interest in vision research, yet most studies have focused on the extraction of mean statistics rather than its dispersion. This study focuses on another aspect of ensemble statistics: the redundancy of the sample. In two experiments, participants were faster judging the facial expression and gender of multiple faces than a single face. The redundancy gain was equivalent for multiple identical faces and for multiple faces of different identities. To test whether the redundancy gain was due to increased strength in perceptual representation, we measured the magnitude of facial expression aftereffects. The aftereffects were equivalent when induced by a single face and by four identical faces, ruling out increased perceptual strength as an explanation for the redundancy gain. We conclude that redundant faces facilitate perception by enhancing the robustness of representation of each face.