# Visual and Haptic Guidance for Enhancing Target Search Performance in Dual-Task Settings
## 2 Related Works
### Visual Displays for Attention Cue and Information Awareness  
Visual guidance can provide consistent assistance to users based on their current location and direction across various digital devices, such as HMDs or mobile screens. This form of user attention guidance can be applied in a wide range of scenarios. For instance, in medical surgery and training, AR visual cues could direct a doctor's attention [1,24]. Visual guidance techniques are also employed in manual assembly assistance systems for target cueing [2]. In tourism navigation information systems, location searching on a digital map is a common task, and visual guidance could assist users in locating nearby points of interest [3].  
Searching for and locating an out-of-view object is a common task for augmented reality (AR) applications on mobile devices and HMDs. Several visual guidance techniques, including halos [6], attention funnels [7], and wedges [8], have been employed to aid users. Among these techniques, arrow guidance can prove to be a straightforward and effective method used to guide user attention [2,4,5]. Arrow guidance typically entails the direction from the user's line of sight toward the position of the out-of-view object. As arrows are familiar to users, they offer high usability and low workload [4]. Arrow cues also exhibit the greatest overall benefit in target searching tasks [5]. In supporting manual assembly assistance systems in target search guidance tasks, arrow guidance has demonstrated the fastest guiding performance [2]. While other dynamic visual effects, like adding background flickering, result in a slow user performance and induce more eye fixation on the arrow rather than searching for the target [2].  
Arrow guidance has been utilized across various computing platforms. For example, 3D arrows have been proven as effective visual cues in mobile AR applications in terms of the target searching performance, workload, and user experience [25]. Arrows are also effective in mobile tourism applications, enabling users to estimate the position of objects more precisely [3]. Furthermore, 3D arrows have proven to be efficient and accurate in densely populated mobile 3D environments, compared to other techniques such as 3 DWedge+ and Halo3D [26]. On HMDs, arrow guidance leads to a faster localization, higher accuracy, lower workload, and slight decrease in physiological stress [27]. It also facilitates the faster recognition of simultaneous events compared to exocentric viewpoint guidance on visual attention [27]. In virtual reality (VR) training environments, arrow guidance aids the guidance and restoration performance [28].  
However, researchers and designers have noted that the presence of cuing to aid target detection for expected targets could divert attention away from unexpected targets in tasks such as piloting an unmanned air vehicles [29], as well as target searching tasks such as in endoscopic navigation exercises [30]. Since shifting attention toward compelling guidance information could have detrimental effects, designers should use strategies to mitigate attention costs. Furthermore, research suggests that visual information placement should avoid the visual center to minimize interference with the visual scene, thereby achieving an optimal visual search [31].