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In practical visual search fields, observers often encounter errors that result from an unknown number of targets, which may induce reduced accuracy and speed. Our current study addresses the potential enhancement of collaborative search efficiency as a dyad to mitigate such incurred search costs. Utilizing the capacity coefficient, we evaluated search efficiency and explored the interplay of task difficulty and termination rule in collaborative visual search. Our prediction that collaborative benefits increased with elevated task difficulty was not supported in Experiment 1, where participants were tasked with judging the presence of any target. In contrast, Experiment 2 demonstrated that dyads exhibited greater search efficiency during exhaustive searches for multiple targets with elevated task difficulty. Notably, our findings indicated an advantage in dyad searches compared to baseline predictions from individual searches. Our results underscored the significance of task difficulty and termination rules in leveraging human resources for improved collaborative visual search performance.

The low-prevalence effect (LPE) is the finding that target detection rates decline as targets become less frequent in a visual search task. A major source of this effect is thought to be that fewer targets result in lower quitting thresholds, i.e., observers respond target-absent after looking at fewer items compared to searches with a higher prevalence of targets. However, a lower quitting threshold does not directly account for an LPE in searches where observers continuously monitor a dynamic display for targets. In these tasks there are no discrete “trials” to which a quitting threshold could be applied. This study examines whether the LPE persists in this type of dynamic search context. Experiment 1 was a 2 (dynamic/static) x 2 (10%/40% prevalence targets) design. Although overall performance was worse in the dynamic task, both tasks showed a similar magnitude LPE. In Experiment 2, we replicated this effect using a task where subjects searched for either of two targets (Ts and Ls). One target appeared infrequently (10%) and the other moderately (40%). Given this method of manipulating prevalence rate, the quitting threshold explanation does not account for the LPE even for static displays. However, replicating Experiment 1, we found an LPE of similar magnitude for both search scenarios, and lower target detection rates with the dynamic displays, demonstrating the LPE is a potential concern for both static and dynamic searches. These findings suggest an activation threshold explanation of the LPE may better account for our observations than the traditional quitting threshold model.

Previous studies have found that emotional states affect the extent of attention, and the effect has been explained by adaptive views. If the adaptive explanations are true, emotion should modulate attentional focus toward a peripheral stimulus. The present study investigated if emotion affects the focus of attention toward a peripheral target in a visual search paradigm with event-related brain potential (ERP) measurement. In each trial of the experiment, participants performed a visual search task after an emotion (unpleasant, neutral, or pleasant) was induced by presenting an international affective picture system (IAPS) image. We measured N2pc, which is an ERP index reflecting attentional focus toward a peripheral target in a visual search, and compared the amplitudes among the emotion conditions. According to the adaptive view of emotional effects on cognition, this study hypothesized that unpleasant emotion would enhance the focus of attention, and pleasant emotion would inhibit it. These hypotheses predicted that N2pc amplitude would increase with unpleasant emotion and decrease with pleasant emotion. However, this study obtained inconsistent results; N2pc amplitude decreased in the unpleasant condition, and there was no significant effect of pleasant emotion on the ERP. The results suggest that unpleasant emotion inhibited the attentional focusing process. This is the first report to examine how emotion modulates the focus of attention toward a peripheral target in a visual search by using ERP. The findings contribute to understanding the relationship between emotion and cognition.

As targets become rare in visual search tasks, the likelihood of missing them increases—a phenomenon known as the low-prevalence effect (LPE). This has important implications for real-world searches, but reducing the LPE has proven challenging. In Experiment 1, we used a low-prevalence T-among-Ls task and found that distributing “probe” trials—trials with known targets and post-response feedback—reduced the LPE. In Experiment 2, participants searched for two low-prevalence targets (T and O among Ls and Qs), and we varied how often each appeared in probe trials. The probe benefit scaled with the frequency of the matching target, suggesting limited generalizability to non-probed targets. Experiment 3 used eye tracking to examine whether probes affected quitting thresholds, decision criteria, or guidance. Results showed that probes biased top-down guidance toward features of frequently probed targets, without affecting the number of items inspected or the decision criterion. In Experiment 4, we tested whether feedback was necessary for the probe benefit. Findings suggest that probes improve rare-target search by altering perceived prevalence, not through feedback alone. Overall, probes may reduce the LPE by increasing perceived prevalence and thereby increasing search guidance, but only when probe targets closely match actual search targets.

Visual search is an integral part of animal life. Two search strategies, intuitive vs. deliberate search, are adopted by almost all animals including humans to adapt to different extent of environmental uncertainty. In two eye-tracking experiments involving simple visual search (Study 1) and complex information search (Study 2), we used the evolutionary life history (LH) approach to investigate the interaction between childhood environmental unpredictability and primed concurrent uncertainty in enabling these two search strategies. The results indicate that when individuals with greater childhood unpredictability were exposed to uncertainty cues, they exhibited intuitive rather than deliberate visual search (i.e., fewer fixations, reduced dwell time, a larger saccade size, and fewer repetitive inspections relative to individuals with lower childhood unpredictability). We conclude that childhood environment is crucial in calibrating LH including visual and cognitive strategies to adaptively respond to current environmental conditions.

Visual inspection of luggage using X-ray technology at airports is a time-sensitive task that is often supported by automated systems to increase performance and reduce workload. The present study evaluated how time pressure and automation support influence visual search behavior and performance in a simulated luggage screening task. Moreover, we also investigated how target expectancy (i.e., targets appearing in a target-often location or not) influenced performance and visual search behavior. We used a paradigm where participants used the mouse to uncover a portion of the screen which allowed us to track how much of the stimulus participants uncovered prior to their decision. Participants were randomly assigned to either a high (5-s time per trial) or a low (10-s time per trial) time-pressure condition. In half of the trials, participants were supported by an automated diagnostic aid (85% reliability) in deciding whether a threat item was present. Moreover, within each half, in target-present trials, targets appeared in a predictable location (i.e., 70% of targets appeared in the same quadrant of the image) to investigate effects of target expectancy. The results revealed better detection performance with low time pressure and faster response times with high time pressure. There was an overall negative effect of automation support because the automation was only moderately reliable. Participants also uncovered a smaller amount of the stimulus under high time pressure in target-absent trials. Target expectancy of target location improved accuracy, speed, and the amount of uncovered space needed for the search. Significance Statement Luggage screening is a safety–critical real-world visual search task which often has to be done under time pressure. The present research found that time pressure compromises performance and increases the risk to miss critical items even with automation support. Moreover, even highly reliable automated support may not improve performance if it does not exceed the manual capabilities of the human screener. Lastly, the present research also showed that heuristic search strategies (e.g., areas where targets appear more often) seem to guide attention also in luggage screening.

Road horizontal curves, which significantly influence drivers’ visual search behavior and are closely linked to traffic safety, also constitute a crucial factor in sustainable road traffic development. This paper uses simulation driving experiments to explore the dynamic response characteristics of 27 typical subject drivers’ visual search behavior regarding road horizontal curve radius. Results show that in a monotonous, open road environment, the driver’s visual search is biased towards the inside of the curve; as the radius increases, the 85th percentile value of the longitudinal visual search length gradually increases, the 85th percentile value of the horizontal search angle gradually decreases, the 85th percentile value of vehicle speed gradually increases, and the dispersion and bias of the gaze points gradually decrease. The search length, horizontal angle, and speed approach the level of straight road sections (380 m, 10° and 115 km/h, respectively). When R ≥ 1200 m, a driver’s dynamic visual search range reaches a stable distribution state that is the same as that of a straight road. A dynamic visual search range distribution model for drivers on straight and horizontal curved road sections is constructed. Based on psychological knowledge such as attention resource theory and eye–mind theory, a human factor engineering explanation was provided for drivers’ attention distribution and speed selection mechanism on road horizontal curve sections. The research results can provide theoretical references for the optimization design of road traffic, decision support to improve the driver training system, and a theoretical basis for determining the visual search characteristics of human drivers in autonomous driving technology, thereby promoting the safe and sustainable development of road traffic.

The use of scene context is a powerful way by which biological organisms guide and facilitate visual search. Although many studies have shown enhancements of target-related electroencephalographic activity (EEG) with synthetic cues, there have been fewer studies demonstrating such enhancements during search with scene context and objects in real world scenes. Here, observers covertly searched for a target in images of real scenes while we used EEG to measure the steady state visual evoked response to objects flickering at different frequencies. The target appeared in its typical contextual location or out of context while we controlled for low-level properties of the image including target saliency against the background and retinal eccentricity. A pattern classifier using EEG activity at the relevant modulated frequencies showed target detection accuracy increased when the target was in a contextually appropriate location. A control condition for which observers searched the same images for a different target orthogonal to the contextual manipulation, resulted in no effects of scene context on classifier performance, confirming that image properties cannot explain the contextual modulations of neural activity. Pattern classifier decisions for individual images were also related to the aggregated observer behavioral decisions for individual images. Together, these findings demonstrate target-related neural responses are modulated by scene context during visual search with real world scenes and can be related to behavioral search decisions.

Plaids consist of two orthogonally oriented gratings. However, their structure may be perceived as a checkerboard with an oblique orientation or as two overlaid gratings. We used a visual search paradigm to investigate how plaids with different perceived structures influence search efficiency for determining whether a preattentive plaid-specific or grating-specific mechanism is involved in representing the plaid. Participants searched for a grating among plaids (Experiment 1) or a plaid among gratings (Experiment 2). Contrast (low vs. high), composed spatial frequency (SF) of the plaid (coherent vs. mixed), and target-distractor orientation relationship (component orientation-aligned vs. structure orientation-aligned) were manipulated to vary the perceived structure of the plaid. Parallel search was observed when the target was a coherent checkerboard plaid, and orientation manipulation did not influence search efficiency. However, search performance was less efficient when the target plaid was perceived as overlaid gratings. When searching for a grating among plaids, low-SF gratings were located more quickly than high-SF gratings, regardless of the plaid distractor type. The results provide evidence for the existence of a preattentive plaid-specific mechanism that is distinct from the grating-sensitive mechanism. KEYWORDS visual search plaid feature integration grating

Background: Although people can pay attention to targets while ignoring distractors, previous research suggests that target enhancement and distractor suppression work separately and independently. Here, we sought to replicate previous findings and re-establish their independence. Methods: We employed an internet-based psychological experiment. We presented participants with a visual search task in which they searched for a specified shape with or without a singleton. We replicated the singleton-presence benefit in search performance, but this effect was limited to cases where the target color was fixed across all trials. In a randomly intermixed probe task (30% of all trials), the participants searched for a letter among colored probes; we used this task to assess how far attention was separately allocated toward the target or distractor dimensions. Results: We found a negative correlation between target enhancement and distractor suppression, indicating that the participants who paid closer attention to target features ignored distractor features less effectively and vice versa. Averaged data showed no benefit from target color or cost from distractor color, possibly because of the substantial differences in strategy across participants. Conclusions: These results suggest that target enhancement and distractor suppression guide attention in mutually dependent ways and that the relative contribution of these components depends on the participants' search strategy.