The Effects of Virtual Audience Size on Social Anxiety during Public Speaking

Prior studies have explored the possibility of inducing social anxiety (SA) in virtual reality (VR). Among various existing protocols for this purpose, the Trier Social Stress Test (TSST) has been proven to be robust in evoking SA in the majority of participants in both in vivo as well as VR conditions. The TSST consists of giving a speech and performing mental arithmetic calculations each for five minutes in front of three persons. In this paper, we present an adaptation of TSST to investigate the effects of different numbers of virtual humans (VHs) (i.e., three, six, or fifteen) on perceived SA. In addition, we compare the results with an in vivo TSST with three real persons in the audience. Twenty four participants took part in this experiment. As a result, physiological arousal could be observed with VR inducing SA yet less than in vivo TSST. Furthermore, some of the subjective measures showed a high state of anxiety experienced during the experiment. An effect of the virtual audience size could be observed only in heart rate (HR) as a virtual audience size of three VHs induced the highest HR responses which was significantly different from an audience of size six and fifteen.