Foreground bias: Semantic consistency effects modulated when searching across depth

When processing visual scenes, we tend to prioritize information in the foreground, often at the expense of background information. The foreground bias has been supported by data demonstrating that there are more fixations to foreground, and faster and more accurate detection of targets embedded in foreground. However, it is also known that semantic consistency is associated with more efficient search. Here, we examined whether semantic context interacts with foreground prioritization, either amplifying or mitigating the effect of target semantic consistency. For each scene, targets were placed in the foreground or background and were either semantically consistent or inconsistent with the context of immediately surrounding depth region. Results indicated faster response times (RTs) for foreground and semantically consistent targets, replicating established effects. More importantly, we found the magnitude of the semantic consistency effect was significantly smaller in the foreground than background region. To examine the robustness of this effect, in Experiment 2, we strengthened the reliability of semantics by increasing the proportion of targets consistent with the scene region to 80%. We found the overall results pattern to replicate the incongruous effect of semantic consistency across depth observed in Experiment 1. This suggests foreground bias modulates the effects of semantics so that performance is less impacted in near space.

Target selection during "snapshot" foraging

While previous foraging studies have identified key variables that determine attentional selection, they are affected by the global statistics of the tasks. In most studies, targets are selected one at a time without replacement while distractor numbers remain constant, steadily reducing the ratios of targets to distractors with every selection. We designed a foraging task with a sequence of local "snapshots" of foraging displays, with each snapshot requiring a target selection. This enabled tighter control of local target and distractor type ratios while maintaining the flavor of a sequential, multiple-target foraging task. Observers saw only six items for each target selection during a "snapshot" containing varying numbers of two target types and two distractor types. After each selection, a new six-item array (the following snapshot) immediately appeared, centered on the locus of the last selected target. We contrasted feature-based and conjunction-based foraging and analyzed the data by the proportion of different target types in each trial. We found that target type proportion affected selection, with longer response times during conjunction foraging when the number of the alternate target types was greater than the repeated target types. In addition, the choice of target in each snapshot was influenced by the relative positions of selected targets and distractors during preceding snapshots. Importantly, this shows to what degree previous findings on foraging can be attributed to changing global statistics of the foraging array. We propose that "snapshot foraging" can increase experimental control in understanding how people choose targets during continuous attentional orienting.

Differential patch-leaving behavior during probabilistic foraging in humans and gerbils

Foraging confronts animals, including humans, with the need to balance exploration and exploitation: exploiting a resource until it depletes and then deciding when to move to a new location for more resources. Research across various species has identified rules for when to leave a depleting patch, influenced by environmental factors like patch quality. Here we compare human and gerbil patch-leaving behavior through two analogous tasks: a visual search for humans and a physical foraging task for gerbils, both involving patches with randomly varying initial rewards that decreased exponentially. Patch-leaving decisions of humans but not gerbils follow an incremental mechanism based on reward encounters that is considered optimal for maximizing reward yields in variable foraging environments. The two species also differ in their giving-up times, and some human subjects tend to overharvest. However, gerbils and individual humans who do not overharvest are equally sensitive to declining collection rates in accordance with the marginal value theorem. Altogether this study introduces a paradigm for a between-species comparison on how to resolve the exploitation-exploration dilemma.

Investigating an effort avoidance account of attentional strategy choice

People often choose suboptimal attentional control strategies during visual search. This has been at least partially attributed to the avoidance of the cognitive effort associated with the optimal strategy, but aspects of the task triggering such avoidance remain unclear. Here, we attempted to measure effort avoidance of an isolated task component to assess whether this component might drive suboptimal behavior. We adopted a modified version of the Adaptive Choice Visual Search (ACVS), a task designed to measure people's visual search strategies. To perform optimally, participants must make a numerosity judgment-estimating and comparing two color sets-before they can advantageously search through the less numerous of the two. If participants skip the numerosity judgment step, they can still perform accurately, albeit substantially more slowly. To study whether effort associated with performing the optional numerosity judgment could be an obstacle to optimal performance, we created a variant of the demand selection task to quantify the avoidance of numerosity judgment effort. Results revealed a robust avoidance of the numerosity judgment, offering a potential explanation for why individuals choose suboptimal strategies in the ACVS task. Nevertheless, we did not find a significant relationship between individual numerosity judgment avoidance and ACVS optimality, and we discussed potential reasons for this lack of an observed relationship. Altogether, our results showed that the effort avoidance for specific subcomponents of a visual search task can be probed and linked to overall strategy choices.

Research on re-searching: interrupted foraging is not disrupted foraging

In classic visual search, observers typically search for the presence of a target in a scene or display. In foraging tasks, there may be multiple targets in the same display (or "patch"). Observers typically search for and collect these target items in one patch until they decide to leave that patch and move to the next one. This is a highly rule-governed behavior. The current study investigated whether these rules are disrupted when the foraging is interrupted in various manners. In Experiment 1, the foraging was briefly interrupted and then resumed in the same patch. In Experiments 2 and 3, the foraging in each patch either ended voluntarily or compulsorily after a fixed amount of time. In these cases, foraging resumed in a patch only after all patches were visited. Overall, the rules of foraging remained largely intact, though Experiment 2 shows that foraging rules can be overridden by the demand characteristics of the task. The results show that participants tended to perform approximately consistently despite interruptions. The results suggest that foraging behavior in a relatively simple foraging environment is resilient and not easily disrupted by interruption.

Joint contributions of preview and task instructions on visual search strategy selection

People tend to employ suboptimal attention control strategies during visual search. Here we question why people are suboptimal, specifically investigating how knowledge of the optimal strategies and the time available to apply such strategies affect strategy use. We used the Adaptive Choice Visual Search (ACVS), a task designed to assess attentional control optimality. We used explicit strategy instructions to manipulate explicit strategy knowledge, and we used display previews to manipulate time to apply the strategies. In the first two experiments, the strategy instructions increased optimality. However, the preview manipulation did not significantly boost optimality for participants who did not receive strategy instruction. Finally, in Experiments 3A and 3B, we jointly manipulated preview and instruction with a larger sample size. Preview and instruction both produced significant main effects; furthermore, they interacted significantly, such that the beneficial effect of instructions emerged with greater preview time. Taken together, these results have important implications for understanding the strategic use of attentional control. Individuals with explicit knowledge of the optimal strategy are more likely to exploit relevant information in their visual environment, but only to the extent that they have the time to do so.

How can I find what I want? Can children, chimpanzees and capuchin monkeys form abstract representations to guide their behavior in a sampling task?

concepts are a powerful tool for making wide-ranging predictions in new situations based on little experience. Whereas looking-time studies suggest an early emergence of this ability in human infancy, other paradigms like the relational match to sample task often fail to detect abstract concepts until late preschool years. Similarly, non-human animals show difficulties and often succeed only after long training regimes. Given the considerable influence of slight task modifications, the conclusiveness of these findings for the development and phylogenetic distribution of abstract reasoning is debated. Here, we tested the abilities of 3 to 5-year-old children, chimpanzees, and capuchin monkeys in a unified and more ecologically valid task design based on the concept of "overhypotheses" (Goodman, 1955). Participants sampled high- and low-valued items from containers that either each offered items of uniform value or a mix of high- and low-valued items. In a test situation, participants should switch away earlier from a container offering low-valued items when they learned that, in general, items within a container are of the same type, but should stay longer if they formed the overhypothesis that containers bear a mix of types. We compared each species' performance to the predictions of a probabilistic hierarchical Bayesian model forming overhypotheses at a first and second level of abstraction, adapted to each species' reward preferences. Children and, to a more limited extent, chimpanzees demonstrated their sensitivity to abstract patterns in the evidence. In contrast, capuchin monkeys did not exhibit conclusive evidence for the ability of abstract knowledge formation.

Testing a relational account of search templates in visual foraging

Search templates guide human visual attention toward relevant targets. Templates are often seen as encoding exact target features, but recent studies suggest that templates rather contain "relational properties" (e.g., they facilitate "redder" stimuli instead of specific hues of red). Such relational guidance seems helpful in naturalistic searches where illumination or perspective renders exact feature values unreliable. So far relational guidance has only been demonstrated in rather artificial single-target search tasks with briefly flashed displays. Here, we investigate whether relational guidance also occurs when humans interact with the search environment for longer durations to collect multiple target elements. In a visual foraging task, participants searched for and collected multiple targets among distractors of different relationships to the target colour. Distractors whose colour differed from the environment in the same direction as the targets reduced foraging efficiency to the same amount as distractors whose colour matched the target colour. Distractors that differed by the same colour distance but in the opposite direction of the target colour did not reduce efficiency. These findings provide evidence that search templates encode relational target features in naturalistic search tasks and suggest that attention guidance based on relational features is a common mode in dynamic, real-world search environments.

Visual search for reach targets in actionable space is influenced by movement costs imposed by obstacles

Real world search tasks often involve action on a target object once it has been located. However, few studies have examined whether movement-related costs associated with acting on located objects influence visual search. Here, using a task in which participants reached to a target object after locating it, we examined whether people take into account obstacles that increase movement-related costs for some regions of the reachable search space but not others. In each trial, a set of 36 objects (4 targets and 32 distractors) were displayed on a vertical screen and participants moved a cursor to a target after locating it. Participants had to fixate on an object to determine whether it was a target or distractor. A rectangular obstacle, of varying length, location, and orientation, was briefly displayed at the start of the trial. Participants controlled the cursor by moving the handle of a robotic manipulandum in a horizontal plane. The handle applied forces to simulate contact between the cursor and the unseen obstacle. We found that search, measured using eye movements, was biased to regions of the search space that could be reached without moving around the obstacle. This result suggests that when deciding where to search, people can incorporate the physical structure of the environment so as to reduce the movement-related cost of subsequently acting on the located target.

Bayesian approximations to the theory of visual attention (TVA) in a foraging task

Foraging as a natural visual search for multiple targets has increasingly been studied in humans in recent years. Here, we aimed to model the differences in foraging strategies between feature and conjunction foraging tasks found by Á. Kristjánsson et al. Bundesen proposed the theory of visual attention (TVA) as a computational model of attentional function that divides the selection process into filtering and pigeonholing. The theory describes a mechanism by which the strength of sensory evidence serves to categorise elements. We combined these ideas to train augmented Naïve Bayesian classifiers using data from Á. Kristjánsson et al. as input. Specifically, we attempted to answer whether it is possible to predict how frequently observers switch between different target types during consecutive selections (switches) during feature and conjunction foraging using Bayesian classifiers. We formulated 11 new parameters that represent key sensory and bias information that could be used for each selection during the foraging task and tested them with multiple Bayesian models. Separate Bayesian networks were trained on feature and conjunction foraging data, and parameters that had no impact on the model's predictability were pruned away. We report high accuracy for switch prediction in both tasks from the classifiers, although the model for conjunction foraging was more accurate. We also report our Bayesian parameters in terms of their theoretical associations with TVA parameters, πj (denoting the pertinence value), and βi (denoting the decision-making bias).

Rational information search in welfare-tradeoff cognition

One of the most important dimensions along which we evaluate others is their propensity to value our welfare: we like people who are disposed to incur costs for our benefit and who refrain from imposing costs on us to benefit themselves. The evolutionary importance of social valuation in our species suggests that humans have cognitive mechanisms that are able to efficiently extract information about how much another person values them. Here I test the hypothesis that people are spontaneously interested in the kinds of events that have the most potential to reveal such information. In two studies, I presented participants (Ns = 216; 300) with pairs of dilemmas that another individual faced in an economic game; for each pair, I asked them to choose the dilemma for which they would most like to see the decision that the individual had made. On average, people spontaneously selected the choices that had the potential to reveal the most information about the individual's valuation of the participant, as quantified by a Bayesian ideal search model. This finding suggests that human cooperation is supported by sophisticated cognitive mechanisms for information-gathering.

Using Gaze for Behavioural Biometrics

A principled approach to the analysis of eye movements for behavioural biometrics is laid down. The approach grounds in foraging theory, which provides a sound basis to capture the uniqueness of individual eye movement behaviour. We propose a composite Ornstein-Uhlenbeck process for quantifying the exploration/exploitation signature characterising the foraging eye behaviour. The relevant parameters of the composite model, inferred from eye-tracking data via Bayesian analysis, are shown to yield a suitable feature set for biometric identification; the latter is eventually accomplished via a classical classification technique. A proof of concept of the method is provided by measuring its identification performance on a publicly available dataset. Data and code for reproducing the analyses are made available. Overall, we argue that the approach offers a fresh view on either the analyses of eye-tracking data and prospective applications in this field.

Visuospatial information foraging describes search behavior in learning latent environmental features

In the real world, making sequences of decisions to achieve goals often depends upon the ability to learn aspects of the environment that are not directly perceptible. Learning these so-called latent features requires seeking information about them. Prior efforts to study latent feature learning often used single decisions, used few features, and failed to distinguish between reward-seeking and information-seeking. To overcome this, we designed a task in which humans and monkeys made a series of choices to search for shapes hidden on a grid. On our task, the effects of reward and information outcomes from uncovering parts of shapes could be disentangled. Members of both species adeptly learned the shapes and preferred to select tiles expected to be informative earlier in trials than previously rewarding ones, searching a part of the grid until their outcomes dropped below the average information outcome-a pattern consistent with foraging behavior. In addition, how quickly humans learned the shapes was predicted by how well their choice sequences matched the foraging pattern, revealing an unexpected connection between foraging and learning. This adaptive search for information may underlie the ability in humans and monkeys to learn latent features to support goal-directed behavior in the long run.

Humans trade off search costs and accuracy in a combined visual search and perceptual task

To interact with one's environment, relevant objects have to be selected as targets for saccadic eye movements. Previous studies have demonstrated that factors such as visual saliency and reward influence saccade target selection, and that humans can dynamically trade off these factors to maximize expected value during visual search. However, expected value in everyday situations not only depends on saliency and reward, but also on the required time to find objects, and the likelihood of a successful object-interaction after search. Here we studied whether search costs and the accuracy to discriminate an object feature can be traded off to maximize expected value. We designed a combined visual search and perceptual discrimination task, where participants chose whether to search for an easy- or difficult-to-discriminate target in search displays populated by distractors that shared features with either the easy or the difficult target. Participants received a monetary reward for correct discriminations and were given limited time to complete as many trials as they could. We found that participants considered their discrimination performance and the search costs when choosing targets and, by this, maximized expected value. However, the accumulated reward was constrained by noise in both the choice of which target to search for, and which elements to fixate during search. We conclude that humans take into account the prospective search time and the likelihood of successful a object-interaction, when deciding what to search for. However, search performance is constrained by noise in decisions about what to search for and how to search for it.

Into the Wild: Biological Timing in Natural Environments

Biological timing (including circadian and interval timing) has mainly focused on rigorously controlled laboratory experiments. There are relatively few studies looking into interval timing behaviors in the wild, which could be understandable due to the complexity of the experimental design but are definitely needed in order to comprehend the adaptive value of such behavior. In this opinion paper we review some of the literature regarding timing observations under field conditions, including reports from birds and mammals, and propose a call-to-action to think about the need of a more naturalistic interpretation of time production and perception, as well as the advantage of designing more ‘natural’ settings in the laboratory.

Satisfaction of Search Can Be Ameliorated by Perceptual Learning: A Proof-of-Principle Study

When searching a visual image that contains multiple target objects of interest, human subjects often show a satisfaction of search (SOS) effect, whereby if the subjects find one target, they are less likely to find additional targets in the image. Reducing SOS or, equivalently, subsequent search miss (SSM), is of great significance in many real-world situations where it is of paramount importance to find all targets in a given image, not just one. However, studies have shown that even highly trained and experienced subjects, such as expert radiologists, are subject to SOS. Here, using the detection of camouflaged objects (or camouflage-breaking) as an illustrative case, we demonstrate that when naïve subjects are trained to detect camouflaged objects more effectively, it has the side effect of reducing subjects’ SOS. We tested subjects in the SOS task before and after they were trained in camouflage-breaking. During SOS testing, subjects viewed naturalistic scenes that contained zero, one, or two targets, depending on the image. As expected, before camouflage-training, subjects showed a strong SOS effect, whereby if they had found a target with relatively high visual saliency in a given image, they were less likely to have also found a lower-saliency target when one existed in the image. Subjects were then trained in the camouflage-breaking task to criterion using non-SOS images, i.e., camouflage images that contained zero or one target. Surprisingly, the trained subjects no longer showed significant levels of SOS. This reduction was specific to the particular background texture in which the subjects received camouflage training; subjects continued to show significant SOS when tested using a different background texture in which they did not receive camouflage training. A separate experiment showed that the reduction in SOS was not attributable to non-specific exposure or practice effects. Together, our results demonstrate that perceptual expertise can, in principle, reduce SOS, even when the perceptual training does not specifically target SOS reduction.

Advances in the application of a computational Theory of Visual Attention (TVA): Moving towards more naturalistic stimuli and game-like tasks

The theory of visual attention, “TVA”, is an influential and formal theory of attentional selection. It is widely applied in clinical assessment of attention and fundamental attention research. However, most TVA-based research is based on accuracy data from letter report experiments performed in controlled laboratory environments. While such basic approaches to questions regarding attentional selection are undoubtedly useful, recent technological advances have enabled the use of increasingly sophisticated experimental paradigms involving more realistic scenarios. Notably, these studies have in many cases resulted in different estimates of capacity limits than those found in studies using traditional TVA-based assessment. Here we review recent developments in TVA-based assessment of attention that goes beyond the use of letter report experiments and experiments performed in controlled laboratory environments. We show that TVA can be used with other tasks and new stimuli, that TVA-based parameter estimation can be embedded into complex scenarios, such as games that can be used to investigate particular problems regarding visual attention, and how TVA-based simulations of “visual foraging” can elucidate attentional control in more naturalistic tasks. We also discuss how these developments may inform future advances of TVA.

Great Minds Think Alike? Spatial Search Processes Can Be More Idiosyncratic When Guided by More Accurate Information

Existing research demonstrates that pre‐decisional information sampling strategies are often stable within a given person while varying greatly across people. However, it remains largely unknown what drives these individual differences, that is, why in some circumstances we collect information more idiosyncratically. In this brief report, we present a pre‐registered online study of spatial search. Using a novel technique that combines machine‐learning dimension reduction and sequence alignment algorithms, we quantify the extent to which the shape and temporal properties of a search trajectory are idiosyncratic. We show that this metric increases (trajectories become more idiosyncratic) when a person is better informed about the likely location of the search target, while poorly informed individuals seem more likely to resort to default search routines determined bottom‐up by the properties of the search field. This shows that when many people independently attempt to solve a task in a similar way, they are not necessarily “onto something.”

Foraging tempo: Human run patterns in multiple-target search are constrained by the rate of successive responses

Human foraging tasks are beginning to provide new insights into the roles of vision, attention, and working memory during complex, multiple-target search. Here, we test the idea that "foraging tempo"-the rate of successive target selections-helps determine patterns of behaviour in these tasks. Previously, we established that the majority of target selections during unconstrained foraging happen at regular, rapid intervals, forming the "cruise phase" of a foraging trial. Furthermore, we noted that when the temporal interval between cruise phase responses was longer, the tendency to switch between target categories increased. To directly explore this relationship, we modified our standard iPad foraging task so that observers had to synchronise each response with an auditory metronome signal. Across trials, we increased the tempo and examined how this changed patterns of foraging when targets were defined either by a single feature or by a conjunction of features. The results were very clear. Increasing tempo systematically decreased the tendency for participants to switch between target categories. Although this was true for both feature and conjunction trials, there was also evidence that time constraints and target complexity interacted. As in our previous work, we also observed clear individual differences in how participants responded to changes in task difficulty. Overall, our results show that foraging tempo does influence the way participants respond, and we suggest this parameter may prove to be useful in further explorations of group and individual strategies during multiple-target search.

Foraging as sampling without replacement: A Bayesian statistical model for estimating biases in target selection

Foraging entails finding multiple targets sequentially. In humans and other animals, a key observation has been a tendency to forage in 'runs' of the same target type. This tendency is context-sensitive, and in humans, it is strongest when the targets are difficult to distinguish from the distractors. Many important questions have yet to be addressed about this and other tendencies in human foraging, and a key limitation is a lack of precise measures of foraging behaviour. The standard measures tend to be run statistics, such as the maximum run length and the number of runs. But these measures are not only interdependent, they are also constrained by the number and distribution of targets, making it difficult to make inferences about the effects of these aspects of the environment on foraging. Moreover, run statistics are underspecified about the underlying cognitive processes determining foraging behaviour. We present an alternative approach: modelling foraging as a procedure of generative sampling without replacement, implemented in a Bayesian multilevel model. This allows us to break behaviour down into a number of biases that influence target selection, such as the proximity of targets and a bias for selecting targets in runs, in a way that is not dependent on the number of targets present. Our method thereby facilitates direct comparison of specific foraging tendencies between search environments that differ in theoretically important dimensions. We demonstrate the use of our model with simulation examples and re-analysis of existing data. We believe our model will provide deeper insights into visual foraging and provide a foundation for further modelling work in this area.

How Psychedelic-Assisted Treatment Works in the Bayesian Brain

Psychedelics are experiencing a renaissance in clinical research. In recent years, an increasing number of studies on psychedelic-assisted treatment have been conducted. So far, the results are promising, suggesting that this new (or rather, rediscovered) form of therapy has great potential. One particular reason for that appears to be the synergistic combination of the pharmacological and psychotherapeutic interventions in psychedelic-assisted treatment. But how exactly do these two interventions complement each other? This paper provides the first account of the interaction between pharmacological and psychological effects in psychedelic-assisted treatment. Building on the relaxed beliefs under psychedelics (REBUS) hypothesis of Carhart-Harris and Friston and the contextual model of Wampold, it argues that psychedelics amplify the common factors and thereby the remedial effects of psychotherapy. More precisely, psychedelics are assumed to attenuate the precision of high-level predictions, making them more revisable by bottom-up input. Psychotherapy constitutes an important source of such input. At best, it signalizes a safe and supportive environment (cf. setting) and induces remedial expectations (cf. set). During treatment, these signals should become incorporated when high-level predictions are revised: a process that is hypothesized to occur as a matter of course in psychotherapy but to get reinforced and accelerated under psychedelics. Ultimately, these revisions should lead to a relief of symptoms.

How the value of the environment controls persistence in visual search

Classic foraging theory predicts that humans and animals aim to gain maximum reward per unit time. However, in standard instrumental conditioning tasks individuals adopt an apparently suboptimal strategy: they respond slowly when the expected value is low. This reward-related bias is often explained as reduced motivation in response to low rewards. Here we present evidence this behavior is associated with a complementary increased motivation to search the environment for alternatives. We trained monkeys to search for reward-related visual targets in environments with different values. We found that the reward-related bias scaled with environment value, was consistent with persistent searching after the target was already found, and was associated with increased exploratory gaze to objects in the environment. A novel computational model of foraging suggests that this search strategy could be adaptive in naturalistic settings where both environments and the objects within them provide partial information about hidden, uncertain rewards.

The selection balance: Contrasting value, proximity and priming in a multitarget foraging task

A critical question in visual foraging concerns the mechanisms driving the next target selection. Observers first identify a set of candidate targets, and then select the best option among these candidates. Recent evidence suggests that target selection relies on internal biases towards proximity (nearest target from the last selection), priming (target from the same category as the last selection) and value (target associated with high value). Here, we tested the role of eye movements in target selection, and notably whether disabling eye movements during target selection could affect search strategy. We asked observers to perform four foraging tasks differing by selection modality and target value. During gaze foraging, participants had to accurately fixate the targets to select them and could not anticipate the next selection with their eyes, while during mouse foraging they selected the targets with mouse clicks and were free to move their eyes. We moreover manipulated both target value and proximity. Our results revealed notable individual differences in search strategy, confirming the existence of internal biases towards value, proximity and priming. Critically, there were no differences in search strategy between mouse and gaze foraging, suggesting that disabling eye movements during target selection did not affect foraging behaviour. These results importantly suggest that overt orienting is not necessary for target selection. This study provides fundamental information for theoretical conceptions of attentional selection, and emphasizes the importance of covert attention for target selection during visual foraging.

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.

Target value and prevalence influence visual foraging in younger and older age

The prevalence and reward-value of targets have an influence on visual search. The strength of the effect of an item's reward-value on attentional selection varies substantially between individuals and is potentially sensitive to aging. We investigated individual and age differences in a hybrid foraging task, in which the prevalence and value of multiple target types was varied. Using optimal foraging theory measures, foraging was more efficient overall in younger than older observers. However, the influence of prevalence and value on target selections was similar across age groups, suggesting that the underlying cognitive mechanisms are preserved in older age. When prevalence was varied but target value was balanced, younger and older observers preferably selected the most frequent target type and were biased to select another instance of the previously selected target type. When value was varied, younger and older observers showed a tendency to select high-value targets, but preferences were more diverse between individuals. When value and prevalence were inversely related, some observers showed particularly strong preferences for high-valued target types, while others showed a preference for high-prevalent, albeit low-value, target types. In younger adults, individual differences in the selection choices correlated with a personality index, suggesting that avoiding selections of low-value targets may be related to reward-seeking behaviour.

Gazing at Social Interactions Between Foraging and Decision Theory

Finding the underlying principles of social attention in humans seems to be essential for the design of the interaction between natural and artificial agents. Here, we focus on the computational modeling of gaze dynamics as exhibited by humans when perceiving socially relevant multimodal information. The audio-visual landscape of social interactions is distilled into a number of multimodal patches that convey different social value, and we work under the general frame of foraging as a tradeoff between local patch exploitation and landscape exploration. We show that the spatio-temporal dynamics of gaze shifts can be parsimoniously described by Langevin-type stochastic differential equations triggering a decision equation over time. In particular, value-based patch choice and handling is reduced to a simple multi-alternative perceptual decision making that relies on a race-to-threshold between independent continuous-time perceptual evidence integrators, each integrator being associated with a patch.

Foraging behavior in visual search: A review of theoretical and mathematical models in humans and animals

Visual search (VS) is a fundamental task in daily life widely studied for over half a century. A variant of the classic paradigm-searching one target among distractors-requires the observer to look for several (undetermined) instances of a target (so-called foraging) or several targets that may appear an undefined number of times (recently named as hybrid foraging). In these searches, besides looking for targets, the observer must decide how much time is needed to exploit the area, and when to quit the search to eventually explore new search options. In fact, visual foraging is a very common search task in the real world, probably involving additional cognitive functions than typical VS. It has been widely studied in natural animal environments, for which several mathematical models have been proposed, and just recently applied to humans: Lévy processes, composite and area-restricted search models, marginal value theorem, and Bayesian learning (among others). We conducted a systematic search in the literature to understand those mathematical models and study its applicability in human visual foraging. The review suggests that these models might be the first step, but they seem to be limited to fully comprehend foraging in visual search. There are essential variables involving human visual foraging still to be established and understood. Indeed, a jointly theoretical interpretation based on the different models reviewed could better account for its understanding. In addition, some other relevant variables, such as certain individual differences or time perception might be crucial to understanding visual foraging in humans.

Great expectations: minor differences in initial instructions have a major impact on visual search in the absence of feedback

Professions such as radiology and aviation security screening that rely on visual search-the act of looking for targets among distractors-often cannot provide operators immediate feedback, which can create situations where performance may be largely driven by the searchers' own expectations. For example, if searchers do not expect relatively hard-to-spot targets to be present in a given search, they may find easy-to-spot targets but systematically quit searching before finding more difficult ones. Without feedback, searchers can create self-fulfilling prophecies where they incorrectly reinforce initial biases (e.g., first assuming and then, perhaps wrongly, concluding hard-to-spot targets are rare). In the current study, two groups of searchers completed an identical visual search task but with just a single difference in their initial task instructions before the experiment started; those in the "high-expectation" condition were told that each trial could have one or two targets present (i.e., correctly implying no target-absent trials) and those in the "low-expectation" condition were told that each trial would have up to two targets (i.e., incorrectly implying there could be target-absent trials). Compared to the high-expectation group, the low-expectation group had a lower hit rate, lower false alarm rate and quit trials more quickly, consistent with a lower quitting threshold (i.e., performing less exhaustive searches) and a potentially higher target-present decision criterion. The expectation effect was present from the start and remained across the experiment-despite exposure to the same true distribution of targets, the groups' performances remained divergent, primarily driven by the different subjective experiences caused by each groups' self-fulfilling prophecies. The effects were limited to the single-targets trials, which provides insights into the mechanisms affected by the initial expectations set by the instructions. In sum, initial expectations can have dramatic influences-searchers who do not expect to find a target, are less likely to find a target as they are more likely to quit searching earlier.

Inhibitory control deficits in vascular cognitive impairment revealed using the MILO task

We used the MILO (Multi-Item Localization) task to characterise the performance of a group of older adults diagnosed with mild to moderate vascular cognitive impairment (VCI). The MILO task is designed to explore the temporal context of visual search and in addition to measuring overall completion time, provides a profile of serial reaction time (SRT) patterns across all items in a sequence. Of particular interest here is the Vanish/Remain MILO manipulation that can identify problems with inhibitory control during search. Typically, SRT functions closely overlap, regardless of whether items Vanish or Remain visible when selected, indicating an ability to ignore previously selected targets. Based on the distributed nature of VCI-related pathology and previous visual search studies from our group, we speculated that MILO performance would be compromised in this group of participants when items remained visible after being selected relative to when they vanished. Compared to cognitively healthy, age-matched control participants, the performance of VCI participants was characterised by overall slowing, increased error rates, and crucially, a compromised ability to ignore past locations. As predicted, the Vanish versus Remain SRT functions of VCI participants significantly diverged towards the end of the sequence, which was not the case for control groups. Overall, our findings suggest that the MILO task could be a useful tool for identifying non-age-related changes in behaviour with patient populations, and more generally hints at a possible inhibitory deficit in VCI.

Foraging with Anne Treisman: Features versus conjunctions, patch leaving and memory for foraged locations

Foraging tasks are increasingly used to investigate human visual attention as they may provide a more dynamic and multifaceted picture of attentional orienting than more traditionally used visual search tasks. A common way of assessing foraging performance involves measuring when foragers decide to move to a new "patch" with a higher yield. We assessed this using Anne Treisman's famous feature versus conjunction manipulation in an iPad foraging task. We measured how well patch leaving accorded with the predictions of the marginal value theorem that describes how foragers may optimize their foraging by leaving a patch once the average yield within a patch drops below the average yield in the whole environment. Human foraging in our paradigm deviated from the predictions of such optimal foraging conceptions, and our participants kept on foraging within the same patch for longer than expected. Patch leaving and intertarget times differed surprisingly little between feature and conjunction foraging, especially in light of the dramatic differences typically seen between performance on feature and conjunction visual search tasks. Other aspects of foraging performance (run number and switch costs) differed strongly between feature and conjunction foraging, however. We conclude that human foraging is probably influenced by too many factors to be captured with a relatively simple mathematical model.

Rethinking Space: A Review of Perception, Attention, and Memory in Scene Processing

Scene processing is fundamentally influenced and constrained by spatial layout and spatial associations with objects. However, semantic information has played a vital role in propelling our understanding of real-world scene perception forward. In this article, we review recent advances in assessing how spatial layout and spatial relations influence scene processing. We examine the organization of the larger environment and how we take full advantage of spatial configurations independently of semantic information. We demonstrate that a clear differentiation of spatial from semantic information is necessary to advance research in the field of scene processing.

Looking ahead: When do you find the next item in foraging visual search?

Many real-world visual tasks involve searching for multiple instances of a target (e.g., picking ripe berries). What strategies do observers use when collecting items in this type of search? Do they wait to finish collecting the current item before starting to look for the next target, or do they search ahead for future targets? We utilized behavioral and eye-tracking measures to distinguish between these two possibilities in foraging search. Experiment 1 used a color wheel technique in which observers searched for T shapes among L shapes while all items independently cycled through a set of colors. Trials were abruptly terminated, and observers reported both the color and location of the next target that they intended to click. Using observers’ color reports to infer target-finding times, we demonstrate that observers found the next item before the time of the click on the current target. We validated these results in Experiment 2 by recording fixation locations around the time of each click. Experiment 3 utilized a different procedure, in which all items were intermittently occluded during the trial. We then calculated a distribution of when targets were visible around the time of each click, allowing us to infer when they were most likely found. In a fourth and final experiment, observers indicated the locations of multiple future targets after the search was abruptly terminated. Together, our results provide converging evidence to demonstrate that observers can find the next target before collecting the current target and can typically forage one to two items ahead.

Searching Through Alternating Sequences: Working Memory and Inhibitory Tagging Mechanisms Revealed Using the MILO Task

We used the Multi-Item Localisation (MILO) task to examine search through two sequences. In Sequential blocks of trials, six letters and six digits were touched in order. In Mixed blocks, participants alternated between letters and digits. These conditions mimic the A and B variants of the Trail Making Test (TMT). In both block types, targets either vanished or remained visible after being touched. There were two key findings. First, in Mixed blocks, reaction times exhibited a saw-tooth pattern, suggesting search for successive pairs of targets. Second, reaction time patterns for vanish and remain conditions were identical in Sequential blocks-indicating that participants could ignore past targets-but diverged in Mixed blocks. This suggests a breakdown of inhibitory tagging. These findings may help explain the elevated completion times observed in TMT-B, relative to TMT-A.

Moving foraging into three dimensions: Feature- versus conjunction-based foraging in virtual reality

Visual attention evolved in a three-dimensional (3D) world, yet studies on human attention in three dimensions are sparse. Here we present findings from a human foraging study in immersive 3D virtual reality. We used a foraging task introduced in Kristjánsson et al. to examine how well their findings generalise to more naturalistic settings. The second goal was to examine what effect the motion of targets and distractors has on inter-target times (ITTs), run patterns, and foraging organisation. Observers foraged for 50 targets among 50 distractors in four different conditions. Targets were distinguished from distractors by either a single feature (feature foraging) or a conjunction of features (conjunction foraging). Furthermore, those conditions were performed both with static and moving targets and distractors. Our results replicate previous foraging studies in many aspects, with constant ITTs during a "cruise-phase" within foraging trials and response time peaks at the end of foraging trials. Some key differences emerged, however, such as more frequent switches between target types during conjunction foraging than previously seen and a lack of clear mid-peaks during conjunction foraging, possibly reflecting that differences between feature and conjunction processing are smaller within 3D environments. Observers initiated their foraging in the bottom part of the visual field and motion did not have much of an effect on selection times between different targets (ITTs) or run behaviour patterns except for the end-peaks. Our results cast new light upon visual attention in 3D environments and highlight how 3D virtual reality studies can provide important extensions to two-dimensional studies of visual attention.

MILO Mobile: An iPad App to Measure Search Performance in Multi-Target Sequences

This article introduces a mobile app version of the Multi-Item Localization (MILO) task. The MILO task was designed to explore the temporal context of search through a sequence and has proven useful in both basic and applied research settings. Here, we describe the basic features of the app and how it can be obtained, installed, and modified. We also provide example data files and present two new sets of empirical data to verify that previous findings concerning prospective planning and retrospective memory (i.e., inhibitory tagging) are reproducible with the app. We conclude by discussing ongoing studies and future modifications that illustrate the flexibility and potential of the MILO Mobile app.

Dynamics of visual attention revealed in foraging tasks

Visual search tasks play a key role in theories of visual attention. But single-target search tasks may provide only a snapshot of attentional orienting. Foraging tasks with multiple targets of different types arguably provide a closer analogy to everyday attentional processing. Set-size effects have in the literature formed the basis for inferring how attention operates during visual search. We therefore measured the effects of absolute set-size (constant target-distractor ratio) and relative set-size (constant set-size but target-distractor ratio varies) on foraging patterns during "feature" foraging (targets differed from distractors on a single feature) and "conjunction" foraging (targets differed from distractors on a combination of two features). Patterns of runs of same target-type selection were similar regardless of whether absolute or relative set-size varied: long sequential runs during conjunction foraging but rapid switching between target types during feature foraging. But although foraging strategies differed between feature and conjunction foraging, surprisingly, intertarget times throughout foraging trials did not differ much between the conditions. Typical response time by set-size patterns for single-target visual search tasks were only observed for the last target during foraging. Furthermore, the foraging patterns within trials involved several distinct phases, that may serve as markers of particular attentional operations. Foraging tasks provide a remarkably intricate picture of attentional selection, far more detailed than traditional single-target visual search tasks, and well-known theories of visual attention have difficulty accounting for key aspects of the observed foraging patterns. Finally, we discuss how theoretical conceptions of attention could be modified to account for these effects.

A serious game to explore human foraging in a 3D environment

Traditional search tasks have taught us much about vision and attention. Recently, several groups have begun to use multiple-target search to explore more complex and temporally extended "foraging" behaviour. Many of these new foraging tasks, however, maintain the simplified 2D displays and response demands associated with traditional, single-target visual search. In this respect, they may fail to capture important aspects of real-world search or foraging behaviour. In the current paper, we present a serious game for mobile platforms, developed in Unity3D, in which human participants play the role of an animal foraging for food in a simulated 3D environment. Game settings can be adjusted, so that, for example, custom target and distractor items can be uploaded, and task parameters, such as the number of target categories or target/distractor ratio are all easy to modify. We are also making the Unity3D project available, so that further modifications can also be made. We demonstrate how the app can be used to address specific research questions by conducting two human foraging experiments. Our results indicate that in this 3D environment, a standard feature/conjunction manipulation does not lead to a reduction in foraging runs, as it is known to do in simple, 2D foraging tasks.

What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures

Interpretation of volumetric medical images represents a rapidly growing proportion of the workload in radiology. However, relatively little is known about the strategies that best guide search behavior when looking for abnormalities in volumetric images. Although there is extensive literature on two-dimensional medical image perception, it is an open question whether the conclusions drawn from these images can be generalized to volumetric images. Importantly, volumetric images have distinct characteristics (e.g., scrolling through depth, smooth-pursuit eye-movements, motion onset cues, etc.) that should be considered in future research. In this manuscript, we will review the literature on medical image perception and discuss relevant findings from basic science that can be used to generate predictions about expertise in volumetric image interpretation. By better understanding search through volumetric images, we may be able to identify common sources of error, characterize the optimal strategies for searching through depth, or develop new training and assessment techniques for radiology residents.

"Satisfaction" in search: Individuals' own search expectations predict their errors in multiple-target search

When people search for multiple targets in a display, finding one target hinders their ability to find additional targets. These errors were originally proposed to stem from a "satisfaction" with finding a first target that leads people to prematurely stop searching. However, empirical evidence for this premise has been elusive, prompting consideration of other theories. We returned to the satisfaction proposal and assessed whether people generate expectations regarding the likelihood of multiple targets that lead to search biases that, in turn, predict the rates at which additional targets are missed. Participants searched for one or two targets among distractors. To measure accuracy, most trials allowed search to progress to completion. The remaining trials terminated when participants had found their first target. In these cases, participants guessed whether an additional (unfound) target was present. The time needed to find a first target was inversely related to the searchers' expectations that a second target would be present. These expectations underestimated objective reality, and the strength of an individual's one-target bias was directly related to his or her likelihood of missing subsequent targets. Thus, people's expectations-based on their own behavior-likely impacted search performance, providing a novel mechanistic explanation for the previously posited "satisfaction-of-search" errors.

Guidance and selection history in hybrid foraging visual search

In Hybrid Foraging tasks, observers search for multiple instances of several types of target. Collecting all the dirty laundry and kitchenware out of a child's room would be a real-world example. How are such foraging episodes structured? A series of four experiments shows that selection of one item from the display makes it more likely that the next item will be of the same type. This pattern holds if the targets are defined by basic features like color and shape but not if they are defined by their identity (e.g., the letters p & d). Additionally, switching between target types during search is expensive in time, with longer response times between successive selections if the target type changes than if they are the same. Finally, the decision to leave a screen/patch for the next screen in these foraging tasks is imperfectly consistent with the predictions of optimal foraging theory. The results of these hybrid foraging studies cast new light on the ways in which prior selection history guides subsequent visual search in general.

A review of eye tracking for understanding and improving diagnostic interpretation

Inspecting digital imaging for primary diagnosis introduces perceptual and cognitive demands for physicians tasked with interpreting visual medical information and arriving at appropriate diagnoses and treatment decisions. The process of medical interpretation and diagnosis involves a complex interplay between visual perception and multiple cognitive processes, including memory retrieval, problem-solving, and decision-making. Eye-tracking technologies are becoming increasingly available in the consumer and research markets and provide novel opportunities to learn more about the interpretive process, including differences between novices and experts, how heuristics and biases shape visual perception and decision-making, and the mechanisms underlying misinterpretation and misdiagnosis. The present review provides an overview of eye-tracking technology, the perceptual and cognitive processes involved in medical interpretation, how eye tracking has been employed to understand medical interpretation and promote medical education and training, and some of the promises and challenges for future applications of this technology.

Visual foraging and executive functions: A developmental perspective

Visual foraging tasks, where participants search for multiple targets at a time, may provide a richer picture of visual attention than traditional single-target visual search tasks. To contribute to the mapping of foraging abilities throughout childhood and to assess whether foraging ability is dependent upon EF abilities, we compared the foraging of 66 children aged 4-7 years (mean age = 5.68 years, SD = 0.97 years, 33 girls), 67 children aged 11-12 years (mean age = 11.80 years, SD = 0.30 years; 36 girls), and 31 adults aged 20-37 (mean age 30.32 years, SD 4.37 years, 18 females) in Iceland, with a task involving multiple targets of different types. We also measured three subdomains of executive functions; inhibition, attentional flexibility, and working memory. Our results show that foraging improves dramatically between the preschool and middle school years, with the older children showing similar foraging abilities as adults due to greater ease of switching between target types. The older children and adults randomly switch between target templates during feature foraging, but exhaustively forage for a single target type before switching during conjunction foraging. Younger children, conversely, tended to also stick to the same target type for long runs during feature foraging, showing that they have difficulties with feature-based tasks. Switch costs were much lower for the older children than the youngest age group, and on par with those of adults, resulting in fast and efficient foraging. Lastly, we found a connection between foraging ability and both working memory and attentional flexibility, but not inhibition. Our study shows that foraging is a promising way of studying visual attention, how it changes throughout the lifespan, and how it is connected to other cognitive functions.