Some puzzling findings in multiple object tracking (MOT): II. Inhibition of moving nontargets

Multiple object tracking in the presence of a goal: Attentional anticipation and suppression

In previous studies, we found that tracking multiple objects involves anticipatory attention, especially in the linear direction, even when a target bounced against a wall. We also showed that active involvement, in which the wall was replaced by a controllable paddle, resulted in increased allocation of attention to the bounce direction. In the current experiments, we wanted to further investigate the potential influence of the valence of the heading of an object. In Experiments 1 and 2, participants were instructed to catch targets with a movable goal. In Experiment 3, participants were instructed to manipulate the permeability of a static wall in order to let targets either approach goals (i.e., green goals) or avoid goals (i.e., red goals). The results of Experiment 1 showed that probe detection ahead of a target that moved in the direction of the goal was higher as compared to probe detection in the direction of a no-goal area. Experiment 2 provided further evidence that the attentional highlighting found in the first experiment depends on the movement direction toward the goal. In Experiment 3, we found that not so much the positive (or neutral) valence (here, the green and no-goal areas) led to increased allocation of attention but rather a negative valence (here the red goals) led to a decreased allocation of attention.

Gender comparison of perceptual-cognitive learning in young athletes

Elite athletes demonstrate higher perceptual cognitive abilities compared to non-athletes and those capacities can be trained. A recent study showed that differences were observed between male and female athletes in their cognitive abilities whereby male athletes showed superior perceptual abilities compared to female athletes. The purpose of this study was to investigate whether there were gender differences in athletes' perceptual cognitive learning using a 3D-MOT tracking task. The study was performed on 72 young people from 16 to 22 years of age; athlete males and females and non-athlete males and females were distributed in four distinct groups. Five sessions comprised of three thresholds were performed with each participant. Results indicated that all participants benefited from training and significantly increased their speed thresholds. Initial scores showed that male athletes achieved higher speed thresholds than any other groups. Furthermore, after 5 weeks, female athletes obtained higher speed thresholds in comparison to their non-athlete counterparts. In conclusion, engaging in sporting activity is associated with improved perceptual-cognitive abilities and learning. The results support the notion that competitive sport-related activity is beneficial for perceptual-cognitive functions and emphasizes the benefits of participating in sport-related activities for improved brain function with an even greater impact for females.

Multiple object tracking with extended occlusions

In everyday life, we often view objects through a limited aperture (e.g., soccer players on TV or cars slipping into our blind spot on a busy road), where objects often move out of view and reappear in a different place later. We modelled this situation in a series of multiple object tracking (MOT) experiments, in which we introduced a cover on the edges of the observed area and manipulated its width. This method introduced systematic occlusions, which were longer than those used in previous MOT studies. Experiment 1 (N = 50) showed that tracking under such conditions is possible, although difficult. An item-level analysis confirmed that people made more errors in targets that were covered longer and more often. In Experiment 2 (N = 50), we manipulated the tracking workload and found that the participants were less affected by the cover when the tracking load was low. In Experiment 3 (N = 50), we asked the participants to keep track of the objects' identities (multiple identity tracking [MIT]). Although MIT is subjectively more demanding, memorising identities improved performance in the most difficult cover conditions. Contrary to previous reports, we also found that even partial occlusions negatively affected tracking.

Disentangling working memory from multiple-object tracking: Evidence from dual-task interferences

Multiple object tracking (MOT) is generally regarded as a pure attention-consuming task that draws heavily on attention resources. In the present study, we adopted a cross-channel visual-audio dual-task paradigm, i.e., the MOT task combined with the concurrent auditory N-back working memory task, to test whether working memory indeed plays a necessary role in the process of multiple tracking, as well as to further identify the specific types of working memory components involved in this process. Experiments 1a and 1b examined the relationship between the MOT task and nonspatial object working memory (OWM) processing by manipulating the tracking load and working memory load, respectively. Results in both experiments indicated that the concurrent nonspatial OWM task did not have a significant effect on the tracking capacity of the MOT task. In contrast, Experiments 2a and 2b examined the relationship between the MOT task and spatial working memory (SWM) processing by a similar approach. Results in both experiments indicated that the concurrent SWM task significantly impaired the tracking capacity of the MOT task, showing a gradual decrease with increasing SWM load. Overall, our study provides empirical evidence that multiple object tracking does involve working memory, primarily related to spatial working memory rather than nonspatial object working memory, which sheds more light on the mechanisms of multiple object tracking.

Inattentional blindness to unexpected hazard in augmented reality head-up display assisted driving: The impact of the relative position between stimulus and augmented graph

OBJECTIVE

An augmented reality head-up display (AR-HUD) is a promising technology in assisted driving. It provides additional information in the driving environment. However, considering the registration problem related to the limitations of interactive technology, we suspect that an AR-HUD may not be able to recognize unpredictable stimuli in a timely manner, inducing inattentional blindness to these non-augmented stimuli. Actually, non-augmented stimuli may accidentally have a brief superimposition to AR graphics. This condition may also influence the rate of inattentional blindness accordingly. Thus, this study examined the problem of inattentional blindness in AR-HUD systems that may result from the immaturity of AR technology.

METHOD

We investigated the impact of AR graphic position (peripheral AOI v.s. central AOI) and the relative position of the AR graphic on unpredictable stimuli (on-HUD hazard v.s. off-HUD hazard) on the occurrence of inattentional blindness. Thirty Participants watched an AR-augmented driving video that included four augmented conditions. Participants were instructed to respond to four critical events (speeding, running of red lights, unexpected pedestrians or motorcycles). The rate of inattentional blindness and response time were recorded. We only analyzed data on unexpected pedestrian and motorcycle incidents.

RESULTS

The relative position of the AR graphic on unpredictable stimuli and AR graphic positions significantly affected the rate of inattentional blindness and response time. Drivers had a higher rate of inattentional blindness to the unpredictable stimulus briefly superimposed on the AR graphic (i.e., on-HUD hazard) in the peripheral visual field (i.e., peripheral AOI). Also, drivers exhibited a higher rate of inattentional blindness to the unpredictable stimuli outside the AR graphic (i.e., off-HUD hazard) in the central visual field (i.e., central AOI).

CONCLUSION

The study is expected to be beneficial for furthering the design of an AR-HUD-assisted system to reduce inattentional blindness in driving. Our results found that in the peripheral visual field, unpredictable stimuli accidentally superimposed on the AR graphic (i.e., on-HUD hazard) lead to a higher probability of ignoring the accidental events and seemed to require a longer response time for drivers. This study illustrated that inattentional blindness to non-augmented stimuli is also influenced by the AR graphic position when AR technology fails to augment them in a timely manner. An important recommendation emerging from this work is to consider the design of AR graphics according to the AR graphic positions and stimulus types to reduce the occurrence of inattentional blindness.

Perceptual cognitive abilities in young athletes: A gender comparison

To achieve optimal performance in sports, it is essential to have strong perceptual cognitive abilities. Evidence suggests that athletes have superior perceptual abilities compared to nonathletes. However, gender differences in athletes’ perceptual cognitive abilities have not been previously reported. This project aims to evaluate perceptual cognitive abilities among male and female adolescents. To measure perceptual abilities, a 3-dimensional multiple-object tracking task was used. The findings confirm the superior perceptual cognitive abilities in young athletes relative to nonathletes. However, our results indicate differences in performance patterns between male and female athletes. These results demonstrate that sports engagement and perceptual cognitive abilities are strongly related during adolescence and that this relationship seems more prevalent in male athletes for this age group.

Exploring the effectiveness of auditory, visual, and audio-visual sensory cues in a multiple object tracking environment

Maintaining object correspondence among multiple moving objects is an essential task of the perceptual system in many everyday life activities. A substantial body of research has confirmed that observers are able to track multiple target objects amongst identical distractors based only on their spatiotemporal information. However, naturalistic tasks typically involve the integration of information from more than one modality, and there is limited research investigating whether auditory and audio-visual cues improve tracking. In two experiments, we asked participants to track either five target objects or three versus five target objects amongst similarly indistinguishable distractor objects for 14 s. During the tracking interval, the target objects bounced occasionally against the boundary of a centralised orange circle. A visual cue, an auditory cue, neither or both coincided with these collisions. Following the motion interval, the participants were asked to indicate all target objects. Across both experiments and both set sizes, our results indicated that visual and auditory cues increased tracking accuracy although visual cues were more effective than auditory cues. Audio-visual cues, however, did not increase tracking performance beyond the level of purely visual cues for both high and low load conditions. We discuss the theoretical implications of our findings for multiple object tracking as well as for the principles of multisensory integration.

Influences of active control on attention allocation in MOT

We investigated the influence of active involvement on the way visual attention is distributed during multiple-object tracking (MOT), specifically when objects bounce, using two experiments modeled after the videogame Pong. In both experiments, participants were either assigned to an active group or a passive group. The active groups were instructed to move a virtual paddle in order to bounce target objects as often as possible. Participants in the passive groups viewed recordings of trials from the active groups. In all conditions, participants were asked to track the target objects and to detect dot probes that briefly appeared on the screen. Using probe detection, we explored the distribution of attentional resources over the linear and bounce trajectories of tracked objects. We found that active involvement can enhance probe detection along the future post-bounce trajectory, but it depends on the difficulty of the task.

Attentional capture in multiple object tracking

Attentional processes are generally assumed to be involved in multiple object tracking (MOT). The attentional capture paradigm is regularly used to study conditions of attentional control. It has up to now not been used to assess influences of sudden onset distractor stimuli in MOT. We investigated whether attentional capture does occur in MOT: Are onset distractors processed at all in dynamic attentional tasks? We found that sudden onset distractors were effective in lowering probe detection, thus demonstrating attentional capture. Tracking performance as dependent measure was not affected. The attentional capture effect persisted in conditions of higher tracking load (Experiment 2) and was dramatically increased in lower presentation frequency of the onset distractor (Experiment 3). Tracking performance was shown to suffer only when onset distractors were presented serially with very short time gaps in between, thus effectively disturbing re-engaging attention on the tracking set (Experiment 4). We discuss that rapid dis- and re-engagement of the attention process on target objects and an additional more basic process that continuously provides location information allow managing strong disruptions of attention during tracking.

Capturing attention improves accommodation: An experimental study in children with ADHD using multiple object tracking

The present study was aimed at assessing the impact of manipulating the attentional load using a multiple object tracking (MOT) task on the dynamics of the accommodative response in children with attention deficit hyperactivity disorder (ADHD). The pupil size was recorded to assess the effectiveness of the experimental manipulation, and the role of ADHD medication was also explored. The accommodative and pupil dynamics (magnitude and variability) were monitored with an open-field autorefractometer (WAM-5500) in 41 children with ADHD (24 non-medicated and 17 medicated) and 21 non-ADHD controls, while they performed the MOT task with four different levels of complexity (i.e., tracking zero, one, two, or three targets). We found that increasing the attentional load caused a heightened accommodative response, showing a negative association between MOT complexity and accommodative lag in children with ADHD and non-ADHD controls. Complementarily, the pupil size increased as a function of task complexity, confirming a successful experimental manipulation. The stability of accommodation was insensitive to the attentional manipulation, but it differed between groups. Specifically, non-medicated children with ADHD exhibited a greater variability of accommodation in comparison to controls. Increasing the attentional load is associated with a reduction in the accommodative lag in children with ADHD and controls. Our findings show that the allocation of attention plays an important role in the dynamics of the accommodative response, which may be of relevance in the diagnosis and treatment of accommodative deficits in children with and without ADHD.

A critical systematic review of the Neurotracker perceptual-cognitive training tool

In this systematic review, we evaluate the scientific evidence behind “Neurotracker,” one of the most popular perceptual-cognitive training tools in sports. The tool, which is also used in rehabilitation and aging research to examine cognitive abilities, uses a 3D multiple object-tracking (MOT) task. In this review, we examine Neurotracker from both a sport science and a basic science perspective. We first summarize the sport science debate regarding the value of general cognitive skill training, based on tools such as Neurotracker, versus sport-specific skill training. We then consider the several hundred MOT publications in cognitive and vision science from the last 30 years that have investigated cognitive functions and object tracking processes. This literature suggests that the abilities underlying object tracking are not those advertised by the Neurotracker manufacturers. With a systematic literature search, we scrutinize the evidence for whether general cognitive skills can be tested and trained with Neurotracker and whether these trained skills transfer to other domains. The literature has major limitations, for example a total absence of preregistered studies, which makes the evidence for improvements for working memory and sustained attention very weak. For other skills as well, the effects are mixed. Only three studies investigated far transfer to ecologically valid tasks, two of which did not find any effect. We provide recommendations for future Neurotracker research to improve the evidence base and for making better use of sport and basic science findings.

Multiple-object tracking and visually guided touch

Multiple-object tracking (MOT) involves keeping track of the positions of multiple independent target items as they move among distractors. According to Pylyshyn (Cognition, 80, 127-158, 2001), the item individuation mechanism used in MOT is also used in visually guided touch. To test this, we compared single-task MOT (MOT alone) with dual-task MOT (MOT while touching items that changed colour), looking for interference: cases where single-task performance was worse than dual-task. Touching items that changed colour interfered with MOT, but effects varied depending on whether the item touched was a target or distractor in MOT. Touching distractors always reduced MOT performance more than touching targets. Touching targets during MOT did not interfere when there was only a single target to track but interfered more once there were two or more targets. We also measured interference based on latencies to touch items that changed colour, comparing single and dual-task conditions (touch alone, touch + track). MOT interfered with touch, increasing RT to touch items that changed colour, with latencies significantly higher when those items were distractors rather than targets. Overall, there was general interference (differences between single and dual-task performance), as might be expected if coordinating the two tasks required a common limited resource such as general attention or working memory. However, there was also differential interference that varied based on whether the touched item was a target or distractor in MOT. This differential interference suggests the specific mechanisms used in MOT may also play a role in visually guided touch.

Adaptive target enhancement determines levels of guidability in Multiple Object Tracking

Flexible resource models suggest that attentional deployment in Multiple Object Tracking either shows in target enhancement or distractor inhibition or both. In order to gauge the influence of these processes we manipulated distinctiveness of targets and distractors along a single dimension by finely grading gray values of objects. We established that a quantitative increase in distinctiveness results in a quantitative increase in tracking performance thus demonstrating a new finding. Further increases of distinctiveness beyond a certain degree produced no further improvements in tracking. This effect, however, was moderated by levels of task difficulty thus providing evidence for the relativity of this effect. With higher task difficulty higher degrees of distinctiveness still resulted in a significant performance gain (Experiment 1). A follow up experiment generalized this finding. By manipulating speed of objects, a situation with a yet higher task difficulty could be established showing that an increase of an already striking distinctiveness can produce an even further performance gain - provided higher task difficulty (Experiment 2). Finally we tested the hypothesis that target enhancement and distractor inhibition are influenced by feature distinctiveness. Although we found possible indications for distractor inhibition, we could not demonstrate an effect of feature distinctiveness on distractor inhibition. Target enhancement, however, was substantially influenced by variation of feature distinctiveness (Experiment 3).

Distinguishing the neural mechanism of attentional control and working memory in feature-based attentive tracking

Surface features are an important component in attentive tracking. However, the neural mechanisms underlying how features affect attentive tracking remain unknown. The present fMRI study addressed this issue by manipulating the intragroup feature complexity and intergroup feature similarity. In particular, this study distinguished the different neural mechanisms of intragroup feature complexity and intergroup feature similarity by investigating the roles of attentional control and working memory in dynamic feature-based attentive tracking. Behavioral and neuroimaging evidence showed that when targets are distinct from distractors, the intragroup feature complexity of the targets, rather than that of the distractors, mainly increases the visual working memory load and significantly activates the frontoparietal cortical circuit. Thus, the involvement of working memory in feature-based attentive tracking is modulated by goal-directed attention control. In addition, when targets are similar to distractors, the intergroup feature similarity (i.e., target-distractor similarity) mainly affects the allocation of attention. Specifically, target-distractor similarity affects the goal-directed attention toward the targets in a stimulus-driven way and induces an interaction between the ventral and dorsal attention networks.

Selection enables enhancement: An integrated model of object tracking

The diversity of research on visual attention and multiple-object tracking presents challenges for anyone hoping to develop a unified account. One key challenge is identifying the attentional limitations that give rise to competition among targets during tracking. To address this challenge, we present a computational model of object tracking that relies on two attentional mechanisms: serial selection and parallel enhancement. Selection picks out an object for further processing, whereas enhancement increases sensitivity to stimuli in regions where objects have been selected previously. In this model, multiple target locations can be tracked in parallel via enhancement, whereas a single target can be selected so that additional information beyond its location can be processed. In simulations of two psychological experiments, we demonstrate that spatial competition during enhancement and temporal competition for selection can explain a range of findings on multiple-object tracking, and we argue that the interaction between selection and enhancement captured in the model is critical to understanding attention more broadly.

How selective attention affects the detection of motion changes with peripheral vision in MOT

In sports, peripheral vision is expected to play an important role in tasks that demand distributed attention and motion-change detection. By using the Multiple-Object-Tracking (MOT) task, these demands were simulated in a well-controlled laboratory environment. Participants tracked four target out of ten moving objects (6 distractors) and pressed a button when one of the ten objects stopped. Detection rates for tracked targets were compared to detection rates of non-tracked distractors at eccentricities between 5° and 25°. The study's aim was to test how the location of attention affects peripheral motion detection. The results show a large attention effect because target stops were detected in 89 % and distractor stops only in 55 % of the trials. Distractor stops were more likely detected when they occurred closer to the fovea while target stops were detected at all eccentricities. That means, orienting attention at target objects facilitates the peripheral detection of their motion changes in monitoring tasks. Having distractors closer to the fovea increases the chance to also detect motion changes of unattended objects. On a theoretical level, results support a tracking mechanism with object-based attention, serial covert attention shifts and flexible but limited attentional resources. On a practical level, sports' experts should use their extensive knowledge to locate attention on most-relevant objects and reduce the eccentricity to other objects to detect motion changes of attended and unattended objects.

The Global Properties of Objects Play the Main Role in Facilitating Multiple Object Tracking Performance

Previous research has revealed the uniqueness-facilitation effect in the multiple object tracking (MOT) task: simple distinct identities and surface features of moving targets could facilitate attentional tracking. By adapting compound stimuli, the present study investigated whether the global or local properties played the main role in the uniqueness-facilitation effect in the MOT task. The uniqueness of local properties, of global properties or of both local and global properties were considered. Observers’ tracking performance in alternative conditions were compared with that in the homogeneous condition wherein all stimuli have identical local and global properties. Results from two experiments suggest that the global properties played the key role in facilitating tracking. The distinctiveness of local properties can also facilitate tracking with global properties being homogeneous. However, when the stimuli’s global properties are distinct from each other—whether the local properties being unique or not—observers’ tracking performance can achieve the same level as that in the unitary-uniqueness condition wherein the moving objects were distinct unitary letters. These results revealed a global superiority effect in the MOT task. Finally, the facilitation effects of the global and local properties might depend on the stimulus sparsity. When the compound stimuli had fewer local elements, the uniqueness facilitation effect on tracking decreased.

The effects of colour complexity and similarity on multiple object tracking performance

Surface features can be used during multiple object tracking (MOT). Previous studies suggested that surface features might be stored in visual working memory to assist object tracking, and attentive tracking and visual working memory share common attentional resources. However, it is still unknown whether features of both the target and distractor sets will be stored, or features of the target and distractor sets are processed differently. Moreover, how feature distinctiveness and similarity between the target and distractor sets affect tracking and allocation of attentional resources are still not clear. First, we manipulated the colour complexity of the target set (CT) and the colour complexity of the distractor set (CD), respectively, in two experiments, where colours of the target and distractor sets were always distinct, to test their effects on tracking performance. If features of the target and distractor sets are stored, manipulating feature complexity of the target and distractor sets would significantly affect tracking performance. Second, this study tested whether tracking performance was affected by different levels of distinctiveness between the target and distractor sets (DTD) and explored how distinctiveness affected tracking and allocation of attentional resources. Results showed that DTD and CT significantly affect tracking performance and allocation of attentional resources, but not CD. These results indicated that when targets and distractors have distinct features, only the surface features of the targets are maintained in visual working memory. And when targets have the same colour with the distractors, they are more difficult and consume more attentional resources to track.

Influence of sports expertise level on attention in multiple object tracking

Background

This study aimed to investigate whether performance in a multiple object tracking (MOT) task could be improved incrementally with sports expertise, and whether differences between experienced and less experienced athletes, or non-athletes, were modulated by load.

Methods

We asked 22 elite and 20 intermediate basketball players, and 23 non-athletes, to perform an MOT task under three attentional load conditions (two, three, and four targets). Accuracies were analyzed to examine whether different levels of sports expertise influence MOT task performance.

Results

The elite athletes displayed better tracking performance compared with the intermediate or non-athletes when tracking three or four targets. However, no significant difference was found between the intermediate athletes and the non-athletes. Further, no differences were observed among the three groups when tracking two targets.

Discussion

The results suggest that the effects of expertise in team ball sports could transfer to a non-sports-specific attention task. These transfer effects to general cognitive functions occur only in elite athletes with extensive training under higher attentional load.

A Vector Field Design Approach to Animated Transitions

Animated transitions can be effective in explaining and exploring a small number of visualizations where there are drastic changes in the scene over a short interval of time. This is especially true if data elements cannot be visually distinguished by other means. Current research in animated transitions has mainly focused on linear transitions (all elements follow straight line paths) or enhancing coordinated motion through bundling of linear trajectories. In this paper, we introduce animated transition design, a technique to build smooth, non-linear transitions for clustered data with either minimal or no user involvement. The technique is flexible and simple to implement, and has the additional advantage that it explicitly enhances coordinated motion and can avoid crowding, which are both important factors to support object tracking in a scene. We investigate its usability, provide preliminary evidence for the effectiveness of this technique through metric evaluations and user study and discuss limitations and future directions.

The semantic category-based grouping in the Multiple Identity Tracking task

In the Multiple Identity Tracking (MIT) task, categorical distinctions between targets and distractors have been found to facilitate tracking (Wei, Zhang, Lyu, & Li in Frontiers in Psychology, 7, 589, 2016). The purpose of this study was to further investigate the reasons for the facilitation effect, through six experiments. The results of Experiments 1-3 excluded the potential explanations of visual distinctiveness, attentional distribution strategy, and a working memory mechanism, respectively. When objects' visual information was preserved and categorical information was removed, the facilitation effect disappeared, suggesting that the visual distinctiveness between targets and distractors was not the main reason for the facilitation effect. Moreover, the facilitation effect was not the result of strategically shifting the attentional distribution, because the targets received more attention than the distractors in all conditions. Additionally, the facilitation effect did not come about because the identities of targets were encoded and stored in visual working memory to assist in the recovery from tracking errors; when working memory was disturbed by the object identities changing during tracking, the facilitation effect still existed. Experiments 4 and 5 showed that observers grouped targets together and segregated them from distractors on the basis of their categorical information. By doing this, observers could largely avoid distractor interference with tracking and improve tracking performance. Finally, Experiment 6 indicated that category-based grouping is not an automatic, but a goal-directed and effortful, strategy. In summary, the present findings show that a semantic category-based target-grouping mechanism exists in the MIT task, which is likely to be the major reason for the tracking facilitation effect.

The effect of negative emotion on multiple object tracking task: An ERP study

Previous studies have revealed that negative emotion may influence participants' cognitive processing. However, the neural mechanism of the impact of negative emotion on dynamic task like Multiple Object Tracking (MOT) is still unknown. This present study used electrophysiological (Event-Related Potentials, ERP) measures to investigate the effect of negative emotion on MOT tasks. Participants were required to complete MOT tasks while detecting the probe dots that would appear on targets, distractors or the space between them during tracking. Results of N2 amplitude showed that the distractor inhibition effect existed only in the neutral emotional picture condition. The P3 amplitude in the parietal area was also modulated by the emotion condition. P3 amplitude in the occipital area showed a target enhancement effect for both the neutral and negative emotion condition. The present study indicates that negative emotion could affect attention resource allocation during MOT.

All eyes on relevance: strategic allocation of attention as a result of feature-based task demands in multiple object tracking

Multiple object tracking (MOT) plays a fundamental role in processing and interpreting dynamic environments. Regarding the type of information utilized by the observer, recent studies reported evidence for the use of object features in an automatic, low- level manner. By introducing a novel paradigm that allowed us to combine tracking with a noninterfering top-down task, we tested whether a voluntary component can regulate the deployment of attention to task-relevant features in a selective manner. In four experiments we found conclusive evidence for a task-driven selection mechanism that guides attention during tracking: The observers were able to ignore or prioritize distinct objects. They marked the distinct (cued) object (target/distractor) more or less often than other objects of the same type (targets /distractors)-but only when they had received an identification task that required them to actively process object features (cues) during tracking. These effects are discussed with regard to existing theoretical approaches to attentive tracking, gaze-cue usability as well as attentional readiness, a term that originally stems from research on attention capture and visual search. Our findings indicate that existing theories of MOT need to be adjusted to allow for flexible top-down, voluntary processing during tracking.

The Categorical Distinction Between Targets and Distractors Facilitates Tracking in Multiple Identity Tracking Task

This study investigates the tracking facilitation effect during categorical distinction between targets and distractors in the Multiple Identity Tracking task. We asked observers to track four targets in a total of eight moving objects, and manipulated categorical distinctions of targets and distractors across four experiments, with different combinations of inter-category and intra-category differences. Results show that tracking performance was significantly better when the targets and distractors were inter-category different, compared to when the targets and distractors were identical or intra-category distinctive. As the inter-category distinction between targets and distractors narrowed, tracking performance improved, but the inter-category facilitation effect decreased. These results may indicate a category-based grouping effect: the observers organized the targets within the same semantic category into one group and made the targets more easily and accurately rediscovered when lost during tracking. Furthermore, the tracking facilitation of categorical distinction diminished when all the objects were inverted. This proved that besides their visual distinctiveness, objects’ semantic category information also played an important role during tracking.

Attention Modulates Spatial Precision in Multiple-Object Tracking

We present a computational model of multiple-object tracking that makes trial-level predictions about the allocation of visual attention and the effect of this allocation on observers' ability to track multiple objects simultaneously. This model follows the intuition that increased attention to a location increases the spatial resolution of its internal representation. Using a combination of empirical and computational experiments, we demonstrate the existence of a tight coupling between cognitive and perceptual resources in this task: Low-level tracking of objects generates bottom-up predictions of error likelihood, and high-level attention allocation selectively reduces error probabilities in attended locations while increasing it at non-attended locations. Whereas earlier models of multiple-object tracking have predicted the big picture relationship between stimulus complexity and response accuracy, our approach makes accurate predictions of both the macro-scale effect of target number and velocity on tracking difficulty and micro-scale variations in difficulty across individual trials and targets arising from the idiosyncratic within-trial interactions of targets and distractors.

Brain Activation of Identity Switching in Multiple Identity Tracking Task

When different objects switch identities in the multiple identity tracking (MIT) task, viewers need to rebind objects’ identity and location, which requires attention. This rebinding helps people identify the regions targets are in (where they need to focus their attention) and inhibit unimportant regions (where distractors are). This study investigated the processing of attentional tracking after identity switching in an adapted MIT task. This experiment used three identity-switching conditions: a target-switching condition (where the target objects switched identities), a distractor-switching condition (where the distractor objects switched identities), and a no-switching condition. Compared to the distractor-switching condition, the target-switching condition elicited greater activation in the frontal eye fields (FEF), intraparietal sulcus (IPS), and visual cortex. Compared to the no-switching condition, the target-switching condition elicited greater activation in the FEF, inferior frontal gyrus (pars orbitalis) (IFG-Orb), IPS, visual cortex, middle temporal lobule, and anterior cingulate cortex. Finally, the distractor-switching condition showed greater activation in the IFG-Orb compared to the no-switching condition. These results suggest that, in the target-switching condition, the FEF and IPS (the dorsal attention network) might be involved in goal-driven attention to targets during attentional tracking. In addition, in the distractor-switching condition, the activation of the IFG-Orb may indicate salient change that pulls attention away automatically.

The Effect of Fearful Expressions on Multiple Face Tracking

How does the visual system realize dynamic tracking? This topic has become popular within cognitive science in recent years. The classical theory argues that multiple object tracking is accomplished via pre-attention visual indexes as part of a cognitively impenetrable low-level visual system. The present research aimed to investigate whether and how tracking processes are influenced by facial expressions that convey abundant social information about one’s mental state and situated environment. The results showed that participants tracked fearful faces more effectively than neutral faces. However, this advantage was only present under the low-attentional load condition, and distractor face emotion did not impact tracking performance. These findings imply that visual tracking is not driven entirely by low-level vision and encapsulated by high-level representations; rather, that facial expressions, a kind of social information, are able to influence dynamic tracking. Furthermore, the effect of fearful expressions on multiple face tracking is mediated by the availability of attentional resources.

Distractor Locations Influence Multiple Object Tracking Beyond Interobject Spacing: Evidence From Equidistant Distractor Displacements

Human observers are able to keep track of several independently moving objects among other objects. Within theories of multiple object tracking (MOT), distractors are assumed to influence tracking performance only by their distance toward the next target. In order to test this assumption, we designed a variant of the MOT paradigm that involved spatially arranged target-distractor pairs and sudden displacements of distractors during a brief flash. Critically, these displacements maintained target-distractor spacing. Our results show that displacing distractors hurts tracking performance (Experiment 1). Importantly, target-distractor confusions occur within target-distractor pairs with displaced distractors (Experiment 2). This displacement effect increases with an increasing displacement angle (Experiment 3) but is equal at different distances between target and distractor (Experiment 4). This finding illustrates that distractors influence tracking performance beyond pure interobject spacing. We discuss how inhibitory processes as well as relations between targets and distractors might interfere with target tracking.

The role of spatial configuration in multiple identity tracking

Background

The simultaneous tracking and identification of multiple moving objects encountered in everyday life requires one to correctly bind identities to objects. In the present study, we investigated the role of spatial configuration made by multiple targets when observers are asked to track multiple moving objects with distinct identities.

Methodology/Principal Findings

The overall spatial configuration made by the targets was manipulated: In the constant condition, the configuration remained as a virtual convex polygon throughout the tracking, and in the collapsed condition, one of the moving targets (critical target) crossed over an edge of the virtual polygon during tracking, destroying it. Identification performance was higher when the configuration remained intact than when it collapsed (Experiments 1a, 1b, and 2). Moreover, destroying the configuration affected the allocation of dynamic attention: the critical target captured more attention than did the other targets. However, observers were worse at identifying the critical target and were more likely to confuse it with the targets that formed the virtual crossed edge (Experiments 3–5). Experiment 6 further showed that the visual system constructs an overall configuration only by using the targets (and not the distractors); identification performance was not affected by whether the distractor violated the spatial configuration.

Conclusions/Significance

In sum, these results suggest that the visual system may integrate targets (but not distractors) into a spatial configuration during multiple identity tracking, which affects the distribution of dynamic attention and the updating of identity-location binding.

Interactive multiple object tracking (iMOT)

We introduce a new task for exploring the relationship between action and attention. In this interactive multiple object tracking (iMOT) task, implemented as an iPad app, participants were presented with a display of multiple, visually identical disks which moved independently. The task was to prevent any collisions during a fixed duration. Participants could perturb object trajectories via the touchscreen. In Experiment 1, we used a staircase procedure to measure the ability to control moving objects. Object speed was set to 1°/s. On average participants could control 8.4 items without collision. Individual control strategies were quite variable, but did not predict overall performance. In Experiment 2, we compared iMOT with standard MOT performance using identical displays. Object speed was set to 2°/s. Participants could reliably control more objects (M = 6.6) than they could track (M = 4.0), but performance in the two tasks was positively correlated. In Experiment 3, we used a dual-task design. Compared to single-task baseline, iMOT performance decreased and MOT performance increased when the two tasks had to be completed together. Overall, these findings suggest: 1) There is a clear limit to the number of items that can be simultaneously controlled, for a given speed and display density; 2) participants can control more items than they can track; 3) task-relevant action appears not to disrupt MOT performance in the current experimental context.

Speed has an effect on multiple-object tracking independently of the number of close encounters between targets and distractors

Multiple-object tracking (MOT) studies have shown that tracking ability declines as object speed increases. However, this might be attributed solely to the increased number of times that target and distractor objects usually pass close to each other ("close encounters") when speed is increased, resulting in more target-distractor confusions. The present study investigates whether speed itself affects MOT ability by using displays in which the number of close encounters is held constant across speeds. Observers viewed several pairs of disks, and each pair rotated about the pair's midpoint and, also, about the center of the display at varying speeds. Results showed that even with the number of close encounters held constant across speeds, increased speed impairs tracking performance, and the effect of speed is greater when the number of targets to be tracked is large. Moreover, neither the effect of number of distractors nor the effect of target-distractor distance was dependent on speed, when speed was isolated from the typical concomitant increase in close encounters. These results imply that increased speed does not impair tracking solely by increasing close encounters. Rather, they support the view that speed affects MOT capacity by requiring more attentional resources to track at higher speeds.

Multiple-object tracking among individuals with Down syndrome and typically developing children

We investigated differences in multiple-object tracking among individuals with Down syndrome (DS) as compared to typically developing children matched on a visual–spatial mental age of approximately 5.5 years. In order to ensure that these effects did not originate in differences in encoding or reporting the positions of targets in distracters after a delay, immediate and delayed report were measured for static items. Although their immediate and delayed report for multiple static items was comparable to that of the typically developing children, the participants with DS performed as if they were only capable of tracking a single item at a time regardless of the number of targets that needed to be tracked. This finding is surprising because the operations used in multiple-object tracking are thought to be necessary for visuospatial tasks, which are an area of relative strength among persons with DS. These results call into question the idea that abilities or deficits in multiple-object tracking predict visuospatial performance, and highlight ways that atypical development can inform our understanding of typical development.

Changing target trajectories influences tracking performance

People have the ability to attentively select and successfully track several moving objects, a process known as multiple-object tracking (MOT; Pylyshyn & Storm Spatial Vision 3: 179-197, 1988). Various factors have been known to influence MOT performance, such as speed, number of distractors, and proximity, while recent work has suggested that object trajectories may also be a factor (Fencsik, Kleiger, & Horowitz Perception and Psychophysics 69: 567-577, 2007). Meanwhile, unexpected changes in motion information have been demonstrated to be a critical facet for attracting attention Howard & Holcombe Attention, Perception & Psychophysics 72: 2087-2095, (2010). Therefore, we suggest that unexpected changes in target trajectories are an important factor in tracking performance. The research presented here controlled for spatial proximity while manipulating the number of instances in which an object changed trajectory. We found that spatial proximity had no effect on tracking performance but, rather, as the number of trajectory changes increased, tracking performance suffered. Results imply that the ability to track multiple moving objects is limited by unexpected changes in direction.

Swapping or dropping? Electrophysiological measures of difficulty during multiple object tracking

In the multiple object tracking task, participants are asked to keep targets separate from identical distractors as all items move randomly. It is well known that simple manipulations such as object speed and number of distractors dramatically alter the number of targets that are successfully tracked, but very little is known about what causes this variation in performance. One possibility is that participants tend to lose track of objects (dropping) more frequently under these conditions. Another is that the tendency to confuse a target with a distractor increases (swapping). These two mechanisms have very different implications for the attentional architecture underlying tracking. However, behavioral data alone cannot differentiate between these possibilities. In the current study, we used an electrophysiological marker of the number of items being actively tracked to assess which type of errors tended to occur during speed and distractor load manipulations. Our neural measures suggest that increased distractor load led to an increased likelihood of confusing targets with distractors while increased speed led to an increased chance of a target item being dropped. Behavioral experiments designed to test this novel prediction support this assertion.

Neuronal correlates of multiple top-down signals during covert tracking of moving objects in macaque prefrontal cortex

Resistance to distraction is a key component of executive functions and is strongly linked to the prefrontal cortex. Recent evidence suggests that neural mechanisms exist for selective suppression of task-irrelevant information. However, neuronal signals related to selective suppression have not yet been identified, whereas nonselective surround suppression, which results from attentional enhancement for relevant stimuli, has been well documented. This study examined single neuron activities in the lateral PFC when monkeys covertly tracked one of randomly moving objects. Although many neurons responded to the target, we also found a group of neurons that exhibited a selective response to the distractor that was visually identical to the target. Because most neurons were insensitive to an additional distractor that explicitly differed in color from the target, the brain seemed to monitor the distractor only when necessary to maintain internal object segregation. Our results suggest that the lateral PFC might provide at least two top-down signals during covert object tracking: one for enhancement of visual processing for the target and the other for selective suppression of visual processing for the distractor. These signals might work together to discriminate objects, thereby regulating both the sensitivity and specificity of target choice during covert object tracking.

Oscillatory synchronization model of attention to moving objects

The world is a dynamic environment hence it is important for the visual system to be able to deploy attention on moving objects and attentively track them. Psychophysical experiments indicate that processes of both attentional enhancement and inhibition are spatially focused on the moving objects; however the mechanisms of these processes are unknown. The studies indicate that the attentional selection of target objects is sustained via a feedforward-feedback loop in the visual cortical hierarchy and only the target objects are represented in attention-related areas. We suggest that feedback from the attention-related areas to early visual areas modulates the activity of neurons; establishes synchronization with respect to a common oscillatory signal for target items via excitatory feedback, and also establishes de-synchronization for distractor items via inhibitory feedback. A two layer computational neural network model with integrate-and-fire neurons is proposed and simulated for simple attentive tracking tasks. Consistent with previous modeling studies, we show that via temporal tagging of neural activity, distractors can be attentively suppressed from propagating to higher levels. However, simulations also suggest attentional enhancement of activity for distractors in the first layer which represents neural substrate dedicated for low level feature processing. Inspired by this enhancement mechanism, we developed a feature based object tracking algorithm with surround processing. Surround processing improved tracking performance by 57% in PETS 2001 dataset, via eliminating target features that are likely to suffer from faulty correspondence assignments.

Beauty is Better Pursued: Effects of Attractiveness in Multiple-Face Tracking

Using the multiple-object tracking paradigm, this study examines how spontaneous appraisal for facial beauty affects distributed attention to multiple faces in dynamic displays. Observers tracked attractive faces more effectively than unattractive faces in this task. Tracking performance was only affected by target attractiveness, suggesting an absence of appraisal for distractor attractiveness. Attractive male faces also produced stronger binding of face identity and location for female participants. Together, the results suggest that facial attractiveness was appraised during tracking even though this was task irrelevant. Contrary to the theory that multiple-object tracking is driven by encapsulated low-level vision, our results show that the content of target representation is not only penetrable by social cognition but also modulates the course of tracking operations.

The Effects of Distractors in Multiple Object Tracking are Modulated by the Similarity of Distractor and Target Features

Is the effect of distractors in multiple object tracking dependent on the distractors sharing the features of the targets? In experiment 1, observers tracked five targets among five distractors that were identical to the targets and a number of additional distractors that were either identical to or featurally distinct from the targets. Results showed that distractors that are distinct from the targets in shape or color, or are stationary, impair tracking less than distractors that are identical to the targets. However, tracking performance declined as the number of distractors increased, even for featurally distinct distractors. Experiment 2 showed that distractors that differ from the targets on two features impair tracking less than distractors that differ from the targets on only one feature, but only when target tracking load is low. These results indicate that shape, color, and motion information about distractors can be used to distinguish them from targets during tracking, although even distractors with a different feature from the targets produce some interference with tracking. These findings suggest that the effect of distractors on tracking is dependent on top–down settings for target features.

Spatial Reference in Multiple Object Tracking

Spatial reference in multiple object tracking is available from configurations of dynamic objects and static reference objects. In three experiments, we studied the use of spatial reference in tracking and in relocating targets after abrupt scene rotations. Observers tracked 1, 2, 3, 4, and 6 targets in 3D scenes, in which white balls moved on a square floor plane. The floor plane was either visible thus providing static spatial reference or it was invisible. Without scene rotations, the configuration of dynamic objects provided sufficient spatial reference and static spatial reference was not advantageous. In contrast, with abrupt scene rotations of 20°, static spatial reference supported in relocating targets. A wireframe floor plane lacking local visual detail was as effective as a checkerboard. Individually colored geometric forms as static reference objects provided no additional benefit either, even if targets were centered on these forms at the abrupt scene rotation. Individualizing the dynamic objects themselves by color for a brief interval around the abrupt scene rotation, however, did improve performance. We conclude that attentional tracking of moving targets proceeds within dynamic configurations but detached from static local background.

Selective Attention Warps Spatial Representation

Selective attention not only influences which objects in a display are perceived, but also directly changes the character of how they are perceived—for example, making attended objects appear larger or sharper. In studies of multiple-object tracking and probe detection, we explored the influence of sustained selective attention on where objects are seen to be in relation to each other in dynamic multi-object displays. Surprisingly, we found that sustained attention can warp the representation of space in a way that is object-specific: In immediate recall of the positions of objects that have just disappeared, space between targets is compressed, whereas space between distractors is expanded. These effects suggest that sustained attention can warp spatial representation in unexpected ways.