Evaluation of Attention Guidance through Visual Subthreshold Stimulus Using a HMD
Authors: Yusuke Maeda, Keiichi Watanuki, Kazunori Kaede
Abstract: Attention guidance is used as a means of conveying important information. Many attention guides use colors or color gradations that stand out from the surrounding environment, such as signs, or directional shapes such as arrows. In the past, some studies have used directional events such as the gaze of others, optical flow, and optical illusions to guide attention. However, such stimulus presentation methods may cause annoyance and discomfort to people because of their high degree of stimulation. For example, when an alert is displayed for a hazard that appears probabilistically when driving a car, it often causes annoyance and discomfort to the driver when the hazard does not appear. In this paper, we propose a new method of alerting the driver by affecting the unconscious region of the brain. In past research, it has been reported that displaying an object in the frame before the visual search task induced attention and shortened the reaction time. In addition, it has been reported that by displaying a short cue during eye movement, the gaze moved in the direction of the cue. The purpose of this study is to evaluate the validity of attentional guidance by presenting such visual subthreshold stimuli. The participants wore a head-mounted display and performed a visual search task in which they had to find and answer one search object different from the others among eight search objects. The time from the start of the visual search task to the finding of the target object and the trajectory of the gaze during the search were used as evaluation indicators. Ten healthy males in their twenties (22.8 years old ± 1.72 years old) with corrected eyesight cooperated in the experiment. The objects to be searched were placed 1 m away from the participants and at 30° to the up, down left, right. A masked image was inserted before the visual search task, and one of the explorers could be seen one frame (Approx. 0.01ms) before the visual search task, which was used as a visual subthreshold stimulus. These cues could be either consistent with or different from the search object to be found. The results of this experiment showed that there was no significant difference in mean reaction time between the three conditions: when the cue matched or differed from the search object to be found, and when the cue was not presented. However, there was a tendency that the position at which the participants first started their search was closer to the location of the cue. This suggests that the threshold stimulus has an effect of inducing attention, but there was no tendency to draw attention strongly. In addition, the speed of recognition was large for some participants, and cues were recognized in some cases. The reason for this result is thought to be the contrast ratio between the cue and the mask image and the presentation position of the cue. Therefore, it is necessary to examine the contrast ratio and the presentation position of the cue for each experimental collaborator.
Keywords: Subthreshold Stimulus, Attention Guidance, Assistant
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