Embodiment in immersive virtual reality increases pupillary responses to a spider climbing a virtual arm

Spider phobia is one of the most common types of specific phobias that can be effectively treated with exposure therapy. During exposure therapy, the patients experience encounters with spiders in a safe environment. Exposure sessions are traditionally performed face-to-face and modulate the intensity of the experience by varying the distance to the feared animal. More recently, immersive virtual reality (VR) has been introduced as an alternative treatment option that allows for novel ways of modulating the experienced intensity. In 23 participants (M age = 31.00), we tested whether embodiment with a virtual arm, or visual realism of a spider, influenced self-rated anxiety and pupillary responses as the spider crawled over the virtual arm. Embodiment was manipulated by asking participants to place their arm congruently (high embodiment) or incongruently (low embodiment) with the virtual arm, and visual realism was manipulated by changing the spider's movement, texture and colour to be either realistic or simple. Differences in pupil size between conditions were analysed with permutation testing, and anxiety ratings with repeated measures ANOVA. Results showed that embodiment with the VR arm increased pupil-size and self-rated anxiety (p < .001). In contrast, increased realism of the spider had no effect on pupil-size or anxiety ratings. Findings support that embodiment in immersive VR intensifies emotional experiences, which could have implications for controlling arousal and anxiety within VR exposure therapy settings.