Visual search training benefits from the integrative effect of enhanced covert attention and optimized overt eye movements

Visual search in a complex environment requires efficient discrimination between target and distractors. Training serves as an effective approach to improve visual search performance when the target does not automatically pop out from the distractors. In the present study, we trained subjects on a conjunction visual search task and examined the training effects in behavior and eye movement from Experiments 1 to 4. The results showed that training improved behavioral performance and reduced the number of saccades and overall scanning time. Training also increased the search initiation time before the first saccade and the proportion of trials in which the subjects correctly identified the target without any saccade, but these effects were modulated by stimulus' parameters. In Experiment 5, we replicated these training effects when eye movements and EEG signals were recorded simultaneously. The results revealed significant N2pc components after the stimulus onset (i.e., stimulus-locked) and before the first saccade (i.e., saccade-locked) when the search target was the trained one. These N2pc components can be considered as the neural signatures for the training-induced boost of covert attention to the trained target. The enhanced covert attention led to a beneficial tradeoff between search initiation time and the number of saccades as a small amount of increase in search initiation time could result in a larger reduction in scanning time. These findings suggest that the enhanced covert attention to target and optimized overt eye movements are coordinated together to facilitate visual search training.

Shear Strength Determination in RC Beams Using ANN Trained with Tabu Search Training Algorithm

The shear failure of reinforced concrete (RC) beams is a critical issue and has attracted the attention of researchers. The specific challenges of shear failure are the numerous factors affecting shear strength, the nonlinear behavior, and the nonlinear relationship between affecting parameters and the concrete properties. This study tackles this challenge by employing Artificial Neural Network (ANN) models. Since, according to No Free Lunch theorem, the performance of optimization algorithms is problem-dependent, this paper aims to assess the feasibility of modeling the shear strength of RC beams using ANNs trained with the Tabu Search Training (TST) algorithm. To this end, 248 experimental results were collected from the literature, and a feed-forward ANN model was employed to predict the shear strength. To assess its feasibility, the ANNs were also modeled using the Particle Swarm Optimization, and Imperialist Competitive Algorithms. As a traditional technique, the multiple regression model was also employed. The shear design equations of ACI-318-2019 were also investigated and compared with Tabu Search Trained ANN model. The analysis of results suggests the superiority of Tabu Search Trained ANNs in comparison to other suggested models in literature and the ACI-318-2019 design code.

The effects of induced optical blur on visual search performance and training

Visual search is a task often used in the rehabilitation of patients with cortical and non-cortical visual pathologies such as visual field loss. Reduced visual acuity is often comorbid with these disorders, and it remains poorly defined how low visual acuity may affect a patient’s ability to recover visual function through visual search training. The two experiments reported here investigated whether induced blurring of vision (from 6/15 to 6/60) in a neurotypical population differentially affected various types of feature search tasks, whether there is a minimal acceptable level of visual acuity required for normal search performance, and whether these factors affected the degree to which participants could improve with training. From the results, it can be seen that reducing visual acuity did reduce search speed, but only for tasks where the target was defined by shape or size (not colour), and only when acuity was worse than 6/15. Furthermore, searching behaviour was seen to improve with training in all three feature search tasks, irrespective of the degree of blurring that was induced. The improvement also generalised to a non-trained search task, indicating that an enhanced search strategy had been developed. These findings have important implications for the use of visual search as a rehabilitation aid for partial visual loss, indicating that individuals with even severe comorbid blurring should still be able to benefit from such training.

Diving in Nose First: The Influence of Unfamiliar Search Scale and Environmental Context on the Search Performance of Volunteer Conservation Detection Dog–Handler Teams

Conservation detection dogs (CDDs) are trained to locate biological material from plants and animals of interest to conservation efforts and are often more effective and economical than other detection methods. However, the financial costs of developing and appropriately caring for CDDs can nonetheless prohibit their use, particularly by smaller conservation organizations. Training skilled volunteers to work with suitable pet dogs may help address this constraint. We sought to further develop the skills of 13 volunteer dog–handler teams that were trained in a previous study to detect myrrh essential oil in controlled laboratory conditions. We assessed search sensitivity, search effort, search precision and false-alert instances through progressive training stages increasing in size and environmental complexity. First, teams searched various-sized areas before and after 12 weeks of search training on a sports-field. Next, teams searched various-sized areas before and after seven weeks of training in bushland. Overall, search sensitivity decreased by approximately 20% in each unfamiliar context, compared to performance in familiar contexts. However, sensitivity typically improved from baseline performance by 10–20% after a period of training. Six teams found at least 78% of targets after training in bushland, yet sensitivity ranged from 29% to 86% between teams. We maintain that the foundational skills developed previously were necessary to prepare volunteer teams for field surveys involving conservation related targets. However, our results highlight the need to also train volunteer CDD teams in search scale and environmental contexts similar to their intended working conditions.

Improved X-ray baggage screening sensitivity with ‘targetless’ search training

When searching for a known target, mental representations of target features, or templates, guide attention towards matching objects and facilitate recognition. When only distractor features are known, distractor templates allow irrelevant objects to be recognised and attention to be shifted away. This is particularly true in X-ray baggage search, a challenging real-world visual search task with implications for public safety, where targets may be unknown, difficult to predict and concealed by an adversary, but distractors are typically benign and easier to identify. In the present study, we draw on basic principles of distractor suppression and rejection to investigate a counterintuitive ‘targetless’ approach to training baggage search. In a simulated X-ray baggage search task, we observed significant benefits to target detection sensitivity (d′) for targetless relative to target-based training, but no effects of performance-contingent rewards or the inclusion of superordinate semantic categories during training. The benefits of targetless search training were most apparent for stimuli involving less spatial overlap (occlusion), which likely represents the difficulty and greater individual variation involved in searching more visually complex images. Together, these results demonstrate the effectiveness of a counterintuitive targetless approach to training target detection in X-ray baggage search, based on basic principles of distractor suppression and rejection, with potential for use as a real-world training tool.

Assessing the learning and transfer of gaze behaviours in immersive virtual reality

Virtual reality (VR) has clear potential for improving simulation training in many industries. Yet, methods for testing the fidelity, validity and training efficacy of VR environments are, in general, lagging behind their adoption. There is limited understanding of how readily skills learned in VR will transfer, and what features of training design will facilitate effective transfer. Two potentially important elements are the psychological fidelity of the environment, and the stimulus correspondence with the transfer context. In this study, we examined the effectiveness of VR for training police room searching procedures, and assessed the corresponding development of perceptual-cognitive skill through eye-tracking indices of search efficiency. Participants (n = 54) were assigned to a VR rule-learning and search training task (FTG), a search only training task (SG) or a no-practice control group (CG). Both FTG and SG developed more efficient search behaviours during the training task, as indexed by increases in saccade size and reductions in search rate. The FTG performed marginally better than the CG on a novel VR transfer test, but no better than the SG. More efficient gaze behaviours learned during training were not, however, evident during the transfer test. These findings demonstrate how VR can be used to develop perceptual-cognitive skills, but also highlight the challenges of achieving transfer of training.

The development of visual search behaviours in immersive virtual reality

Virtual reality (VR) has clear potential for improving simulation training in many industries. Yet, methods for testing the fidelity, validity and training efficacy of VR environments is, in general, lagging behind their adoption. In this study we examined the effectiveness of VR for training Police room searching procedures, and assessed the corresponding development of perceptual-cognitive expertise through eye-tracking indices of search efficiency. Participants (n=54) were assigned to a VR rule-learning and search training game, a search only training game or a no-practice control group. The VR search training group developed more efficient search behaviours (indexed by saccade size, search rate and gaze entropy) and performed better than controls on a novel transfer test. Efficient gaze behaviours learned during training were not, however, evident during the transfer test. These findings demonstrate how VR can be used to develop perceptual-cognitive skills, but also highlight the challenges of achieving transfer of training.

Exemplar learning reveals the representational origins of expert category perception

Irrespective of whether one has substantial perceptual expertise for a class of stimuli, an observer invariably encounters novel exemplars from this class. To understand how novel exemplars are represented, we examined the extent to which previous experience with a category constrains the acquisition and nature of representation of subsequent exemplars from that category. Participants completed a perceptual training paradigm with either novel other-race faces (category of experience) or novel computer-generated objects (YUFOs) that included pairwise similarity ratings at the beginning, middle, and end of training, and a 20-d visual search training task on a subset of category exemplars. Analyses of pairwise similarity ratings revealed multiple dissociations between the representational spaces for those learning faces and those learning YUFOs. First, representational distance changes were more selective for faces than YUFOs; trained faces exhibited greater magnitude in representational distance change relative to untrained faces, whereas this trained–untrained distance change was much smaller for YUFOs. Second, there was a difference in where the representational distance changes were observed; for faces, representations that were closer together before training exhibited a greater distance change relative to those that were farther apart before training. For YUFOs, however, the distance changes occurred more uniformly across representational space. Last, there was a decrease in dimensionality of the representational space after training on YUFOs, but not after training on faces. Together, these findings demonstrate how previous category experience governs representational patterns of exemplar learning as well as the underlying dimensionality of the representational space.

Effect of Visual Search Training on Saccades in Age-related Macular Degeneration Subjects

Objective: To compare the impact of unilateral versus bilateral Age-related Macular Degeneration (AMD) on saccadic movements, and to show the effect of visual search training on these eye movement performances in AMD subjects. We hypothesized that unilateral and bilateral AMD subjects had abnormal saccadic performances, and that visual search training could improve their performances. Methods: Three groups participated in visual search training: 13 elderly unilateral AMD subjects (mean age: 74.6 ± 1.6 years), 15 elderly bilateral AMD subjects (mean age: 74.2 ± 1.2 years), and 15 healthy age-matched control subjects (mean age: 70.9 ± 1.3 years). Horizontal saccadic performances were recorded before and after visual search training (Metrisquare®) with the Mobile Eye Tracker (Mobile EBT®). We analyzed the saccadic movement performances: latency, mean velocity and gain. We measured the training performances for each exercise: the time, the number of omissions and the number of errors. We analyzed the performances with Kruskal-Wallis and posthoc tests. Results: The latency of saccades in AMD subjects is significantly longer compared to healthy elderly for 15° (p<0.03), 10° (p<0.003) and 5° (p<10-3). Unilateral and bilateral AMD subjects normalized their latency of saccades after training for small saccades (respectively p=0.30 and p=0.23 for 10°, and p=0.09 and p=0.52 for 5°). In elderly, performances depend on the saccade’s amplitude. Conclusion: AMD subjects’ saccadic movements are disrupted: the execution needs more time but is efficient. The visual search training improved the saccadic performances in AMD subjects. Further studies will aim to improve knowledge on such issues and to explore the benefit of training over time in unilateral AMD subjects.