## 4 The Pilot Study
### Measures. Emotions experienced in VR
#### 4.2.1 EEG measures  
EEG data were recorded (sampling rate: 100 Hz) using an Emotiv EPOC(r) helmet (www.emotiv.com). Raw EEG data from 14 locations (AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6, F4, F8, and AF4) were stored for each virtual scenario session and each participant and processed off-line using MATLAB 2019a. Using the pipeline applied in former experiments [29], the following processing steps were applied to raw data that corresponded to the entire duration of the scenario session: (1) artefact rejection through an ICA-based procedure [30]; (2) selection of the channels that displayed an SNR, calculated as the ratio of the power in the 3-30 Hz bandwidth and that of the 30-64 Hz bandwidth, which was higher than 3 dB; and (3) band-pass filtering of the data (finite impulse response with 500 samples; frequency range: 3-40 Hz). To estimate power spectral density (PSD), [PERSON]'s method was used, with the data segmented into 1-s-long windows and 50% overlap. Then, to compute the EEG indicators for each channel, PSD was segmented into the following EEG bands, and the power contained in each one was calculated: \(\alpha\) (8-13 Hz), \(\beta\) (13-30 Hz), \(\beta_{\text{low}}\) (13-15 Hz), \(\beta_{\text{high}}\) (23-30 Hz),  
Figure 1: Examples of experimental conditions created by crossing the ethnicity and social appearance of the confederate: (**a**) black confederate dressed as a businessman; (**b**) black confederate dressed casually; and (**c**) white confederate dressed as a beggar.  
and \(\theta\) (4-8 Hz). The values of the indicators described below were then calculated as averages for the selected channels.  
1. Calmness Index (TBR)  
The calmness index (theta-beta ratio, or TBR) was calculated based on the ratio between the beta band and theta band (see Equation (1)) [31]. A decrease in beta band power (which leads to higher TBR) is associated with a decrease in information processing, which leads to a more relaxed condition. TBR has been shown to be negatively correlated to attention and anxiety [31]. Conversely, it increases when the level of attention decreases, and thus it is defined an objective marker of executive cognitive control [32].  
\[TBR=\frac{\theta}{\beta} \tag{1}\]  
2. Engagement Index (EI)  
The engagement index (EI) was obtained by considering alpha, beta, and theta activities (see Equation (2)). An increase in beta activity is directly related to task engagement, while an increase in alpha and theta activities reflects relaxation, a low level of alertness, and a decrease in information processing [33; 34]. An increase in the EI index reflects an increase in the level of engagement [35].  
\[\text{EI}=\beta/(\alpha+\theta) \tag{2}\]  
3. Alertness Index (BBR)  
The alertness index (beta-beta ratio, or BBR) was calculated based on the ratio between the upper beta band and the lower beta band (see Equation (3)) [36]. It has been shown that an increase in \(\beta\)high is linked to an increase in alertness and strain [37], while an increase in \(\beta\)low can be linked to an increase in inattention [36; 37]. Therefore, an increase in BBR may indicate an increase in alertness and attention levels.  
\[\text{BBR}=\beta_{\text{high}}/\beta_{\text{low}} \tag{3}\]